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Sample records for grain-size trends inferred

  1. Comparing spatial grain-size trends inferred from textural parameters using percentile statistical parameters and those based on the log-hyperbolic method

    DEFF Research Database (Denmark)

    Bartholdy, Jesper; Christiansen, C.; Pedersen, Jørn Bjarke Torp

    2007-01-01

    -size distributions, there seems to be a general defect in the log-hyperbolic approximation of the best represented tail. This makes ¿ less sensitive to indicate the correct sign of slightly skewed grain-size distributions than Sk. However, when examining trends, the relative change between ¿ and Sk by and large......, exclusively linked to dynamic sorting. In general, the F&W parameters reflect the observed grain-size trends far better than the corresponding log-hyperbolic parameters. The log-hyperbolic "typical log grain size", ¿, is sensitive to changes in skewness and cannot replace mean grain size, Mz, in grain......The Folk&Ward (F&W) and the log-hyperbolic methods are applied to a small - and easy to overlook - number of typical sand sized grain-size distributions from the Danish Wadden Sea. The sand originates from the same source, and the pattern of change in the grain-size distributions is, therefore...

  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. 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. 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.

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

    Science.gov (United States)

    Li, Tao; Li, Tuan-Jie

    2017-07-01

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

  6. The Effects of Nourishments Using the Grain-Size Trend Analysis on the Intertidal Zone at a Sandy Macrotidal Beach

    Science.gov (United States)

    Choi, J. Y.; Park, J. Y.; Choi, J. H.; Choi, T. J.

    2016-02-01

    Byeonsan Beach is one of the typical macro-tidal beach on the west coast of South Korea, that has been eroded continuously over the past decade, especially after the construction of Seamangum Dike. Starting from 2011, artificial nourishment was conducted on Byeonsan Beach every year, with nearly 8 × 103 m3of well sorted medium sands over the intertidal flat area. Primary purposes of the present study are to understand the pattern of sediment transport using the grain-size trend analysis (GSTA) proposed by Gao and Collins (1992), and to evaluate the effect of nourishment procedures. Because of the monsoonal climate, nourishments are carried out just before the rainy summer season between late May and early Jun. More than 120 surface sediments are collected carefully each times in March before nourishment and also in September about 3-month after nourishment, and the results are considered as representing the equilibrium status of transport pattern in the previous winter season and during summer after nourishment, respectively. Beach morphology was also made monthly by using RTK-GPS system. The result showed that most of the nourished sands remained within the tidalflat-beach system, and thus the nourishment procedures conducted on Byeonsan Beach are considered as successful. Surficial sediments were transported dominantly landward direction from intertidal zone of nourished area, resulting the 20 cm increase in mean elevation along the upper sand beach (Figure 1). Subsequent amounts of nourished sand are considered to be transported seaward direction showing different transport patterns between 2013 and 2014, especially at the northern and southern part of the beach. Local factors influencing the transport pattern are the amount of rainfalls and the resulting outflows from the sluice gates, and the climatic conditions such as strong typhoons in summer and the northwester during winter.

  7. Simulating grain size estimation

    Czech Academy of Sciences Publication Activity Database

    Saxl, Ivan; Sülleiová, K.; Ponížil, P.

    2001-01-01

    Roč. 39, č. 6 (2001), s. 396-409 ISSN 0023-432X R&D Projects: GA ČR GA201/99/0269 Keywords : grain size estimation% ASTM standards%Voronoi tessellations Subject RIV: BE - Theoretical Physics Impact factor: 0.343, year: 2001

  8. 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 bars. Thus, it is advantageous to analyze suspended-sediment concentration and grain-size data to infer changes in the topographic distribution and grain size of the upstream bed sediment. Rubin and Topping (2001) developed and tested a theory-based technique that can be used for this purpose. Their parameter "β " is a nondimensional measure of the average bed-surface grain-size that interacts with the suspended sediment in the flow. Analyses of the laser-acoustic datasets indicate that, when the Colorado River is relatively enriched with respect to finer sand, the discharge of water, and the concentration and grain size of the suspended sand are all positively correlated. During these periods, β is negatively correlated with discharge, indicating that the sand on the bed is finer at higher elevations along the banks. Although water discharge and the concentration of suspended sand remain positively correlated when the river is relatively depleted in finer sand, grain size of suspended sand then becomes negatively correlated with both the discharge of water and suspended-sand concentration. The greater decrease in β as a function of discharge demonstrates the decrease in the grain size of the bed sand as a function of elevation is much greater under sand-depleted conditions than under sand-enriched conditions. Thus, these analyses indicate that, during periods of erosion, sand is winnowed preferentially from lower elevations along the river.

  9. 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.

  10. Grain-size distribution of volcaniclastic rocks 2: Characterizing grain size and hydraulic sorting

    Science.gov (United States)

    Jutzeler, Martin; McPhie, Jocelyn; Allen, Sharon R.; Proussevitch, A. A.

    2015-08-01

    Quantification of the grain size distribution of sediments allows interpretation of processes of transport and deposition. Jutzeler et al. (2012) developed a technique to determine grain size distribution of consolidated clastic rocks using functional stereology, allowing direct comparison between unconsolidated sediments and rocks. Here, we develop this technique to characterize hydraulic sorting and infer transport and deposition processes. We compare computed grain size and sorting of volcaniclastic rocks with field-based characteristics of volcaniclastic facies for which transport and depositional mechanisms have been inferred. We studied pumice-rich, subaqueous facies of volcaniclastic rocks from the Oligocene Ohanapecosh Formation (Ancestral Cascades, Washington, USA), Pliocene Dogashima Formation (Izu Peninsula, Honshu, Japan), Miocene Manukau Subgroup (Northland, New Zealand) and the Quaternary Sierra La Primavera caldera (Jalisco State, Mexico). These sequences differ in bed thickness, grading and abundance of matrix. We propose to evaluate grain size and sorting of volcaniclastic deposits by values of their modes, matrix proportion (< 2 mm; F-1) and D16, instead of median diameter (D50) and standard deviation parameters. F-1 and D16 can be uniformly used to characterize and compare sieving and functional stereology data. Volcaniclastic deposits typically consist of mixtures of particles that vary greatly in density and porosity. Hydraulic sorting ratios can be used to test whether mixed clast populations of pumice and dense clasts are hydraulically sorted with each other, considering various types of transport underwater. Evaluation of this ratio for our samples shows that most studied volcaniclastic facies are deposited by settling from density currents, and that basal dense clast breccias are emplaced by shear rolling. These hydraulic sorting ratios can be applied to any type of clastic rocks, and indifferently on consolidated and unconsolidated samples.

  11. 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

  12. 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...

  13. 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.

  14. Grain size estimation in anisotropic materials

    Czech Academy of Sciences Publication Activity Database

    Saxl, Ivan; Ponížil, P.; Sülleiová, K.

    2005-01-01

    Roč. 482, - (2005), s. 239-242 ISSN 0255-5476 R&D Projects: GA ČR(CZ) GA201/03/0946 Institutional research plan: CEZ:AV0Z10190503 Keywords : 3D grain size * profile count * intercept count Subject RIV: BB - Applied Statistics, Operational Research Impact factor: 0.399, year: 2005

  15. Grain Size Estimation in Anisotropic Materials

    Czech Academy of Sciences Publication Activity Database

    Procházka, J.; Ponížil, P.; Saxl, Ivan

    2008-01-01

    Roč. 568, č. 2 (2008), s. 285-288 ISSN 0255-5476 R&D Projects: GA ČR GA201/06/0302 Institutional research plan: CEZ:AV0Z10190503 Keywords : grain size estimation * anisotropy * planmar sections Subject RIV: JP - Industrial Processing

  16. Solid Particle Erosion of Nanocrystalline Nickel Coatings: Influence of Grain Size and Adiabatic Shear Bands

    Science.gov (United States)

    Wasekar, Nitin P.; Haridoss, Prathap; Sundararajan, G.

    2018-02-01

    The primary objective of the present study is to investigate the influence of nanocrystalline grain size on the solid particle erosion behavior of nickel. For the above purpose, 450- μm-thick nanocrystalline Ni coatings having the average grain sizes of 21, 42, 70, and 195 nm were obtained using pulsed electrodeposition (PED). All these samples along with bulk annealed Ni samples (43 μm grain size) were subjected to solid particle erosion using SiO2 particles as an erodent at a constant impact velocity of 45 m/s and two impact angles (30 and 90 deg). Erosion results indicate that bulk Ni and PED Ni coatings of grain sizes 195 and 70 nm exhibit the same erosion rate, while PED Ni coatings of 42 and 21 nm grain size exhibit marginally higher erosion rates with a clear trend of increasing erosion rate with decreasing grain size. It was also observed that the higher erosion rates exhibited by 21- and 42-nm-grain size PED Ni samples were associated with the formation of adiabatic shear bands (ASBs) originating from the eroded surface and propagating into the eroded sample. The experimental observations have been understood on the basis of a transition from a localization model for erosion for coarse-grained Ni (> 70 nm) to an ASB-induced erosion model for grain sizes less than 70 nm.

  17. Grain size mapping in shallow rivers using spectral information: a lab spectroradiometry perspective

    Science.gov (United States)

    Niroumand-Jadidi, Milad; Vitti, Alfonso

    2017-10-01

    Every individual attribute of a riverine environment defines the overall spectral signature to be observed by an optical sensor. The spectral characteristic of riverbed is influenced not only by the type but also the roughness of substrates. Motivated by this assumption, potential of optical imagery for mapping grain size of shallow rivers (channel. To address these drawbacks, this study examines the effectiveness of spectral information to make distinction among grain sizes for submerged substrates. Spectroscopic experiments are performed in controlled condition of a hydraulic lab. The spectra are collected over a water flume in a range of water depths and bottoms with several grain sizes. A spectral convolution is performed to match the spectra to WorldView-2 spectral bands. The material type of substrates is considered the same for all the experiments with only variable roughness/size of grains. The spectra observed over dry beds revealed that the brightness/reflectance increases with the grain size across all the spectral bands. Based on this finding, the above-water spectra over a river channel are simulated considering different grain sizes in the bottom. A water column correction method is then used to retrieve the bottom reflectances. Then the inferred bottom reflectances are clustered to segregate among grain sizes. The results indicate high potential of the spectral approach for clustering grain sizes (overall accuracy of 92%) which opens up some horizons for mapping this valuable attribute of rivers using remotely sensed data.

  18. 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.)

  19. Inferring population trends of Araucaria angustifolia (Araucariaceae ...

    African Journals Online (AJOL)

    Matrix population models may generate important information to prevent undesirable outcomes for endangered species. This is the case for Araucaria angustifolia, a Critically Endangered conifer, with little knowledge regarding its life history and trends in development over time. This study sought to investigate life-history ...

  20. International Conference on Trends and Perspectives in Linear Statistical Inference

    CERN Document Server

    Rosen, Dietrich

    2018-01-01

    This volume features selected contributions on a variety of topics related to linear statistical inference. The peer-reviewed papers from the International Conference on Trends and Perspectives in Linear Statistical Inference (LinStat 2016) held in Istanbul, Turkey, 22-25 August 2016, cover topics in both theoretical and applied statistics, such as linear models, high-dimensional statistics, computational statistics, the design of experiments, and multivariate analysis. The book is intended for statisticians, Ph.D. students, and professionals who are interested in statistical inference. .

  1. On the anomalous grain size dependence of spall strength

    Science.gov (United States)

    Wilkerson, Justin; Ramesh, Kt

    2017-06-01

    Experimental studies have identified an anomalous grain size dependence of spall strength in a few face-centered cubic metals. Here we derive the first quantitative theory capable of explaining this phenomena. The theory agrees well with experimental measurements and atomistic calculations over a very wide range of conditions. Utilizing this theory, we are able to map out three distinct regimes in which spall strength (i) increases with decreasing grain size in accordance with conventional wisdom, (ii) non-intuitively decreases with decreasing grain size, and (iii) is independent of grain size. The theory also predicts microscopic characteristics of the spall fracture surface, which agree with available data.

  2. Unfolding grain size effects in barium titanate ferroelectric ceramics

    Science.gov (United States)

    Tan, Yongqiang; Zhang, Jialiang; Wu, Yanqing; Wang, Chunlei; Koval, Vladimir; Shi, Baogui; Ye, Haitao; McKinnon, Ruth; Viola, Giuseppe; Yan, Haixue

    2015-01-01

    Grain size effects on the physical properties of polycrystalline ferroelectrics have been extensively studied for decades; however there are still major controversies regarding the dependence of the piezoelectric and ferroelectric properties on the grain size. Dense BaTiO3 ceramics with different grain sizes were fabricated by either conventional sintering or spark plasma sintering using micro- and nano-sized powders. The results show that the grain size effect on the dielectric permittivity is nearly independent of the sintering method and starting powder used. A peak in the permittivity is observed in all the ceramics with a grain size near 1 μm and can be attributed to a maximum domain wall density and mobility. The piezoelectric coefficient d33 and remnant polarization Pr show diverse grain size effects depending on the particle size of the starting powder and sintering temperature. This suggests that besides domain wall density, other factors such as back fields and point defects, which influence the domain wall mobility, could be responsible for the different grain size dependence observed in the dielectric and piezoelectric/ferroelectric properties. In cases where point defects are not the dominant contributor, the piezoelectric constant d33 and the remnant polarization Pr increase with increasing grain size. PMID:25951408

  3. Unfolding grain size effects in barium titanate ferroelectric ceramics.

    Science.gov (United States)

    Tan, Yongqiang; Zhang, Jialiang; Wu, Yanqing; Wang, Chunlei; Koval, Vladimir; Shi, Baogui; Ye, Haitao; McKinnon, Ruth; Viola, Giuseppe; Yan, Haixue

    2015-05-07

    Grain size effects on the physical properties of polycrystalline ferroelectrics have been extensively studied for decades; however there are still major controversies regarding the dependence of the piezoelectric and ferroelectric properties on the grain size. Dense BaTiO3 ceramics with different grain sizes were fabricated by either conventional sintering or spark plasma sintering using micro- and nano-sized powders. The results show that the grain size effect on the dielectric permittivity is nearly independent of the sintering method and starting powder used. A peak in the permittivity is observed in all the ceramics with a grain size near 1 μm and can be attributed to a maximum domain wall density and mobility. The piezoelectric coefficient d33 and remnant polarization Pr show diverse grain size effects depending on the particle size of the starting powder and sintering temperature. This suggests that besides domain wall density, other factors such as back fields and point defects, which influence the domain wall mobility, could be responsible for the different grain size dependence observed in the dielectric and piezoelectric/ferroelectric properties. In cases where point defects are not the dominant contributor, the piezoelectric constant d33 and the remnant polarization Pr increase with increasing grain size.

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

    Science.gov (United States)

    Shi, Jing; Wang, Yachao; Yang, Xiaoping

    2013-11-22

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

  5. 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

  6. 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

  7. 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...

  8. Unraveling the Anomalous Grain Size Dependence of Cavitation

    Science.gov (United States)

    Wilkerson, J. W.; Ramesh, K. T.

    2016-11-01

    Experimental studies have identified an anomalous grain size dependence associated with the critical tensile pressure that a metal may sustain before catastrophic failure by cavitation processes. Here we derive the first quantitative theory (and its associated closed-form solution) capable of explaining this phenomena. The theory agrees well with experimental measurements and atomistic calculations over a very wide range of conditions. Utilizing this theory, we are able to map out three distinct regimes in which the critical tensile pressure for cavitation failure (i) increases with decreasing grain size in accordance with conventional wisdom, (ii) nonintuitively decreases with decreasing grain size, and (iii) is independent of grain size. The theory also predicts microscopic signatures of the cavitation process which agree with available data.

  9. 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

  10. 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 (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 identified in bulk sediment ɛNd compositions over the last 20 k.y., and that overall provenance trends remain consistent with previous findings.

  11. 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.

  12. 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.

  13. GRAIN SIZE CONSTRAINTS ON HL TAU WITH POLARIZATION SIGNATURE

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-20

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

  14. Grain size, stress and creep in polycrystalline solids

    CSIR Research Space (South Africa)

    Nabarro, FRN

    2000-08-01

    Full Text Available creep. Fig. 3. Diagram for aluminum augmented by the line w(s ) determining the dislocation cell size. Where w < L, power- law breakdown occurs at a stress independent of grain size. PHYSICS OF THE SOLID STATE Vol. 42 No. 8 2000 GRAIN SIZE...-7834/00/4208- $20.00 ? 2000 MAIK ?Nauka/Interperiodica? Physics of the Solid State, Vol. 42, No. 8, 2000, pp. 1456?1459. From Fizika Tverdogo Tela, Vol. 42, No. 8, 2000, pp. 1417?1419. Original English Text Copyright ? 2000 by Nabarro. 1. DIFFUSIONAL CREEP...

  15. 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...

  16. 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 ...

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

    Indian Academy of Sciences (India)

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

  18. Prediction of grain size evolution for low alloyed steels

    Science.gov (United States)

    Dub, Vladimir; Churyumov, Alexandr; Rodin, Alexey; Belikov, Sergey; Barbolin, Alexey

    2018-03-01

    The microstructure of the low alloyed steels after hot plastic deformation and high temperature annealing was described for different regimes of treatment. It was shown, that using of the Avrami- Kolmogorov type equation allows to predict the grain size with accuracy about 7%.

  19. Universal scaling of grain size distributions during dislocation creep

    Science.gov (United States)

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

    2017-04-01

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

  20. 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.

  1. Material grain size and crack size influences on cleavage fracturing.

    Science.gov (United States)

    Armstrong, Ronald W

    2015-03-28

    A review is given of the analogous dependence on reciprocal square root of grain size or crack size of fracture strength measurements reported for steel and other potentially brittle materials. The two dependencies have much in common. For onset of cleavage in steel, attention is focused on relationship of the essentially athermal fracture stress compared with a quite different viscoplastic yield stress behaviour. Both grain-size-dependent stresses are accounted for in terms of dislocation pile-up mechanics. Lowering of the cleavage stress occurs in steel because of carbide cracking. For crack size dependence, there is complication of localized crack tip plasticity in fracture mechanics measurements. Crack-size-dependent conventional and indentation fracture mechanics measurements are described also for results obtained on the diverse materials: polymethylmethacrylate, silicon crystals, alumina polycrystals and WC-Co (cermet) composites. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  2. Grain size evaluation of metallic specimens using laser-ultrasonics

    International Nuclear Information System (INIS)

    Lim, Chung Soo; Park, Hyung Kook; Jeon, Hyung Ha; Kim, Dal Woo; Oh, Ki Jang; Hong, Soon Taek

    2002-01-01

    The laser-ultrasonics inspection techniques for the measurement of grain size have been developed in this study. The ultrasonics are generated by pulsed Nd:YAG laser and the pulse energy is 300 mJ and wavelength is 1064 nm. Since the frequency bandwidth of laser-ultrasonics generated by pulsed laser is extremely broad, this laser-ultrasonics are suitable for analysis of frequency dependence of ultrasonic attenuation. The attenuation coefficients (α) in thick steel plates are measured by using laser-ultrasonics of 15 MHz and 30 MHz, which is probed by confocal Fabry-Perot interferometer. The results show that the attenuation coefficients are closely related with grain size and high frequency ultrasonics are more effective to measure the fine pain size. According to the experimental results of this study, we can conclude that laser-ultrasonics inspection is effective method for grain size measurement. The confocal Fabry-Perot interferometer has been developed for non-contact measurement of laser-ultrasonics. The transmittance characteristic of interferometer has been studied experimentally with CW single-mode laser system. The results show that the Fabry-Perot interferometer is a very effective tool for the measurement of ultrasonics. Using the developed Fabry-Perot interferometer, we have measured ultrasonic signals of high temperature specimen up to 1200 degrees C.

  3. 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.

  4. 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.

  5. 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

    references Betzer, P.R., Carder, K.L., Duce, R.A., Merrill, J.T., Tindale, N.W., Uematsu, M., Costello, D.K., Young, R.W., Feely, R.A., Breland, J.A., Bernstein, R.E., Greco, A.M., 1988. Long-range transport of giant mineral aerosol particles. Nature 336, 568. Claquin, T., Roelandt, C., Kohfeld, K.E., Harrison, S.P., Tegen, I., C., P.I., Balkanski, Y., Bergametti, G., Hansson, M., Mahowald, N.M., Rodhe, H., Schulz, M., 2003. Radiative forcing of climate by ice-age atmospheric dust. Climate Dynamics 20, 193-202. Holz, C., Stuut, J.-B.W., Henrich, R., 2004. Terrigenous sedimentation processes along the continental margin off NW-Africa: implications from grain-size analyses of surface sediments. Sedimentology 51, 1145-1154. Otto, S., de Reus, M., Trautmann, T., Thomas, A., Wendisch, M., Borrmann, S., 2007. Atmospheric radiative effects of an in situ measured Saharan dust plume and the role of large particles. Atmos. Chem. Phys. 7, 4887-4903. Prins, M.A., Weltje, G.J., 1999. End-member modeling of siliciclastic grain-size distributions: the Late Quaternary record of eolian and fluvial sediment supply to the Arabian Sea and its paleoclimatic significance., in: Harbaugh, J., Watney, L., Rankey, G., Slingerland, R., Goldstein, R., Franseen, E. (Eds.), Numerical experiments in stratigraphy: Recent advances in stratigraphic and sedimentologic computer simulations. SEPM Special Publication 62. Society for Sedimentary Geology, pp. 91-111. Prins, M.A., Vriend, M., 2007, Glacial and interglacial eolian dust dispersal patterns across the Chinese Loess Plateau inferred from decomposed loess grain-size records. Geochemistry, Geophysics, Geosystems (G-cubed), 8, Q07Q05, doi:10.1029/2006GC001563. Prins, M.A., Vriend, M., Nugteren, G., Vandenberghe, J., Lu, H., Zheng, H., Jan Weltje, G., 2007. Late Quaternary aeolian dust input variability on the Chinese Loess Plateau: inferences from unmixing of loess grain-size records. Quaternary Science Reviews 26, 230-242. Prins, M.A., Zheng, H., Beets, K

  6. Grain Size Measurements of Eolian Ripples in Gale Crater, Mars

    Science.gov (United States)

    Weitz, C. M.; Sullivan, R. J., Jr.; Lapotre, M. G. A.; Rowland, S. K.; Edgett, K. S.; Grant, J. A., III; Yingst, R. A.

    2017-12-01

    The Curiosity rover team has explored several different eolian sand targets in Gale crater, including dunes and ripples. Using Curiosity's Mars Hand Lens Imager (MAHLI), we measured the size of grains on or near ripple crests within dunes, ripple fields, and in isolated ripples. The Barby target (Sol 1184) is on the crest of a ripple on the lower stoss slope of the barchan High dune. Flume Ridge (Sol 1604) and Avery Peak (Sol 1651) are smaller ripples on the Nathan Bridges and Mount Desert Island linear dunes. Schoolhouse Ledge (Sol 1688) is an isolated megaripple not associated with either a dune or ripple field. Enchanted Island (Sol 1751) is a ripple contained within a larger ripple field near the Vera Rubin Ridge. Our results show the grains of the Avery Peak and Flume Ridge targets are mostly 75-150 µm in size and grain motion was observed during each MAHLI imaging sequence. Barby is dominated by 250-450 µm grains assumed to be active based upon the lack of a dust coating, though grain motion was not observed. The Enchanted Island target has slightly larger grains than Barby, with most between 300-500 µm. The grains have some dust aggregates on their surfaces, suggesting they have been less active in recent months or years relative to the ripples examined within the Bagnold dune field. Finally, grains along the crest of Schoolhouse Ledge are the largest, 400-600 µm, and all of the grain surfaces have a thin dust coating, indicating the ripple is not currently active. Some of the ripple crests have similar grain sizes on both the stoss and lee sides (Schoolhouse Ledge, Barby) whereas other ripples showed larger grains concentrated on the stoss side (Enchanted Island, Avery Peak, Flume Ridge). Scuffing by the rover's front wheel revealed both Schoolhouse Ledge and Enchanted Island had coarser grains dominating the ripple surface with finer grains within the ripple interior. In general, the surfaces of active sand ripples have smaller grains compared to the

  7. Ion beam sputter deposition of Ag films: Influence of process parameters on electrical and optical properties, and average grain sizes

    International Nuclear Information System (INIS)

    Bundesmann, C.; Feder, R.; Gerlach, J.W.; Neumann, H.

    2014-01-01

    Ion beam sputter deposition is used to grow several sets of Ag films under systematic variation of ion beam parameters, such as ion species and ion energy, and geometrical parameters, such as ion incidence angle and polar emission angle. The films are characterized concerning their thickness by profilometry, their electrical properties by 4-point-probe-measurements, their optical properties by spectroscopic ellipsometry, and their average grain sizes by X-ray diffraction. Systematic influences of the growth parameters on film properties are revealed. The film thicknesses show a cosine-like angular distribution. The electrical resistivity increases for all sets with increasing emission angle and is found to be considerably smaller for Ag films grown by sputtering with Xe ions than for the Ag films grown by sputtering with Ar ions. Increasing the ion energy or the ion incidence angle also increases the electrical resistivity. The optical properties, which are the result of free charge carrier absorption, follow the same trends. The observed trends can be partly assigned to changes in the average grain size, which are tentatively attributed to different energetic and angular distributions of the sputtered and back-scattered particles. - Highlights: • Ion beam sputter deposition under systematic variation of process parameters. • Film characterization: thickness, electrical, optical and structural properties. • Electrical resistivity changes considerably with ion species and polar emission angle. • Electrical and optical data reveal a strong correlation with grain sizes. • Change of film properties related to changing properties of film-forming particles

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

    DEFF Research Database (Denmark)

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

    2011-01-01

    We review methods to estimate the average crystal (grain) size and the crystal (grain) size distribution in solid rocks. Average grain sizes often provide the base for stress estimates or rheological calculations requiring the quantification of grain sizes in a rock’s microstructure. The primary...... 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...

  9. 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

  10. 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.

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

    DEFF Research Database (Denmark)

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

    2002-01-01

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

  13. grain size and heat source effect on the drying profile of cocoa bean

    African Journals Online (AJOL)

    eobe

    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 four different grain sizes samples (A, B, C, D) was subjected to drying till 13 subjected to drying till 13 subjected to drying till 13-14% moisture co.

  14. Eyewitness Recall: Regulation of Grain Size and the Role of Confidence

    Science.gov (United States)

    Weber, Nathan; Brewer, Neil

    2008-01-01

    Eyewitness testimony plays a critical role in Western legal systems. Three experiments extended M. Goldsmith, A. Koriat, and A. Weinberg-Eliezer's (2002) framework of the regulation of grain size (precision vs. coarseness) of memory reports to eyewitness memory. In 2 experiments, the grain size of responses had a large impact on memory accuracy.…

  15. Estimation of grain sizes and mixing ratios of fine powder mixtures of common geologic minerals

    Science.gov (United States)

    Hiroi, Takahiro; Pieters, Carle M.

    1994-01-01

    Two different approaches for modeling reflectance spectra of intimate mixtures, Hapke's model and the isograin model, are used to estimate grain sizes and mixing ratios of powder mixtures of three geologic minerals: olivine, orthopyroxene, and plagioclase. In Hapke's model, scattering and extinction effiencies are mixed separately, and both models employ semiempirical refractive index spectra for component minerals. Mixing ratios of mixtures of grain size 45-75 micrometers are well estimated by both models assuming a common grain size of 60 micrometers and optimizing the constants for the single-particle scattering. For each model, effective grain size ratios for mineral constituents in mixtures of grain size less than 25 micrometers, are derived successfully that allows mineral abundances to be accurately predicted within approximately 4 wt percent. On the other hand, neither model can accurately predict mineral reflectance spectra for its smaller grain sizes less than 25 and 25-45 micrometers using an absorption coefficient spectrum derived from a larger grain size (45-75 micrometers). The errors in both models are significantly reduced if surface roughness effects of the smaller grain-size fractions are modeled.

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

    Science.gov (United States)

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

    2016-12-01

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

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

    DEFF Research Database (Denmark)

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

    1974-01-01

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

  18. Inference

    DEFF Research Database (Denmark)

    Møller, Jesper

    2010-01-01

    Chapter 9: This contribution concerns statistical inference for parametric models used in stochastic geometry and based on quick and simple simulation free procedures as well as more comprehensive methods based on a maximum likelihood or Bayesian approach combined with markov chain Monte Carlo...... (MCMC) techniques. Due to space limitations the focus is on spatial point processes....

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

    Science.gov (United States)

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

    2017-12-01

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

  20. 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.

  1. Transport and mixing of eolian sand from local sources resulting in variations in grain size in a gypsum dune field, White Sands, New Mexico, USA

    Science.gov (United States)

    Langford, Richard P.; Gill, Thomas E.; Jones, Slade B.

    2016-03-01

    The White Sands Dune Field, New Mexico (USA), provides a unique opportunity to study sources and eolian transport of sand. End member mixing analysis provides unbiased correlation of the grain size distributions of populations that mix sands from four different local source surface types. Textural differences between sources allow local transport paths to be deduced. In total, 1214 surface samples from 10 dunes and 2 downwind-oriented transects were collected. Neither elevation on the dune, lee or stoss location nor distance downwind correlated with mean grain size, coarsest 10% (D90), or sorting. Instead, grain size distributions are controlled by mixing of locally sourced sand populations. Adjacent dunes can have different mean grain sizes, resulting from different local source populations. Local within-dune and between-dune variability resulting from different sand sources dominates any larger-scale trends across and within dunes. Four sand populations are identified, based on microscopically observable differences in grain size, shape and angularity. Each correlates with high loading of a different statistical factor, derived from End Member Mixing Analysis. End Member 1 (EM1) correlates with well-sorted populations of finer-grained, equant, rounded sands. EM2 correlates with samples that contain moderately sorted populations containing angular blades and crystal aggregates associated with erosional interdunes. EM3 is associated with samples of moderately to poorly sorted fine-grained sand containing fine sand-sized gypsum needles collected from areas of vegetated interdunes, and EM4 is associated with moderately well sorted coarse- and very coarse-grained sands collected from granule ripples. These results suggest that downwind mixing of different populations and segregation by different depositional processes influence grain size distributions in the dune field, rather than by dune-scale or erg-scale transport and sorting.

  2. 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

  3. Inference

    DEFF Research Database (Denmark)

    Møller, Jesper

    (This text written by Jesper Møller, Aalborg University, is submitted for the collection ‘Stochastic Geometry: Highlights, Interactions and New Perspectives', edited by Wilfrid S. Kendall and Ilya Molchanov, to be published by ClarendonPress, Oxford, and planned to appear as Section 4.1 with the ......(This text written by Jesper Møller, Aalborg University, is submitted for the collection ‘Stochastic Geometry: Highlights, Interactions and New Perspectives', edited by Wilfrid S. Kendall and Ilya Molchanov, to be published by ClarendonPress, Oxford, and planned to appear as Section 4.......1 with the title ‘Inference'.) This contribution concerns statistical inference for parametric models used in stochastic geometry and based on quick and simple simulation free procedures as well as more comprehensive methods using Markov chain Monte Carlo (MCMC) simulations. Due to space limitations the focus...

  4. Grain size dependence of coercivity of sintered Nd-Fe-B permanent magnets

    International Nuclear Information System (INIS)

    Tang Weizhong; Zhou Shouzeng; Hu Bing

    1991-01-01

    The grain size dependence of intrinsic coercivity H c of sintered Nd-Fe-B permanent magnets is investigated. It is confirmed that small grain sizes are connected with high Hc values, and that for magnets with different grain sizes, their coercivity can be expressed by the formula μ 0 H c =N c (kμ 0 H A -N i I s ), where H A and I s denote the magnetic anisotropy field and spontaneous magnetization of the hard magnetic Nd 2 Fe 14 B phase, respectively, and k and N i are thought to be two constants related to the perfectness and the demagnetization field of isolated grains, and N e a parameter inversely changing with the grain size. It is suggested that in analyzing the coercivity mechanism of the Nd-Fe-B magnets, the effect of magnetic interactions between individual magnetic grains should also be considered. (orig.)

  5. Effect of graphene grains size on the microwave electromagnetic shielding effectiveness of graphene/polymer multilayers

    Science.gov (United States)

    Kuzhir, Polina P.; Paddubskaya, Alesia G.; Volynets, Nadzeya I.; Batrakov, Konstantin G.; Maksimenko, Sergey A.; Golubeva, Elena N.; Valusis, Gintaras; Kaplas, Tommi; Reckinger, Nicolas; Lobet, Michael; Lambin, Philippe

    2017-07-01

    The influence of chemical vapor deposition (CVD) graphene grain size on the electromagnetic (EM) shielding performance of graphene/polymethyl methacrylate (PMMA) multilayers in Ka-band was studied both experimentally and theoretically. We found that increasing the average graphene grain size from 20 to 400 μm does not change the EM properties of heterostructures consisting of graphene layers sandwiched between submicron thick PMMA spacers. The independence of EM interference shielding effectiveness on the graphene grain size between 20 and 400 μm allows one to use cheaper (or more convenient regimes of CVD) graphene samples with low crystallinity and small grain size in the development of new graphene-based passive EM devices operated at high frequencies.

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

    DEFF Research Database (Denmark)

    Liu, Hong-Sheng; Mishnaevsky, Leon

    2013-01-01

    A computational model of martensitic phase transformation in nanostructured nitinol is developed which takes into account the grain size effect. On the basis of the theoretical analysis of the thermodynamic transformation criterion and the energy barrier for phase transformation, it was demonstra......A computational model of martensitic phase transformation in nanostructured nitinol is developed which takes into account the grain size effect. On the basis of the theoretical analysis of the thermodynamic transformation criterion and the energy barrier for phase transformation...... transformation are totally suppressed. Graded and localized distributions of grain sizes of nitinol were compared with nitinol samples with homogeneous grain size distribution. In the materials with localized region of small grains, it was observed that the martensite rich regions form first on the border...

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

    Data.gov (United States)

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

  8. 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...

  9. 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...

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

    Digital Repository Service at National Institute of Oceanography (India)

    De, C.; Chakraborty, B.

    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...

  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. Grain-size signature of Saharan dust over the Atlantic Ocean at 12°N

    Science.gov (United States)

    van der Does, Michelle; Korte, Laura; Munday, Chris; Brummer, Geert-Jan; Stuut, Jan-Berend

    2015-04-01

    Every year, an estimated 200 million tons of Saharan dust are deposited in the Atlantic Ocean. On its way from source to sink, the dust can be influenced by many climatic processes, but it also affects climate itself in various ways that are far from understood. In order to constrain the relations between atmospheric dust and climate, we deployed ten submarine sediment traps along a transect in the Atlantic Ocean at 12˚N, at 1200m and 3500m water depth. These have been sampling Saharan dust settling in the ocean since October 2012. Samples of seven of these sediment traps have been successfully recovered during RV Pelagia cruise 64PE378 in November 2013. The transect also includes three floating dust collectors and two on-land dust collectors, and all the instruments lie directly underneath the largest dust plume originating from the African continent. This study focuses on the size of the dust particles, which can have an effect on the positive or negative radiation balance in the atmosphere. Small particles in the high atmosphere can reflect incoming radiation and therefore have a cooling effect on climate. Large particles in the lower atmosphere have the opposite effect by absorbing reflected radiation from the Earth's surface. Mineral dust also affects carbon export to the deep ocean by providing mineral ballast for organic particles, and the size of the dust particles directly relates to the downward transport velocity. Here I will present the measured grain-size distributions of samples from seven sediment traps recovered from the 12°N-latitude transect. The data show seasonal variations, with finer grained dust particles during winter and spring, and coarser grained particles during summer and fall. Samples from multiple years should give more details about the dust's seasonality. Also a fining trend of the grain sizes of the dust particles from source (Africa) to sink (Caribbean) is observed, which is also expected due to intuitive relationships between

  13. 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

  14. Static Recrystallized Grain Size of Coarse-Grained Austenite in an API-X70 Pipeline Steel

    Science.gov (United States)

    Sha, Qingyun; Li, Guiyan; Li, Dahang

    2013-12-01

    The effects of initial grain size and strain on the static recrystallized grain size of coarse-grained austenite in an API-X70 steel microalloyed with Nb, V, and Ti were investigated using a Gleeble-3800 thermomechanical simulator. The results indicate that the static recrystallized grain size of coarse-grained austenite decreases with decreasing initial grain size and increasing applied strain. The addition of microalloying elements can lead to a smaller initial grain size for hot deformation due to the grain growth inhibition during reheating, resulting in decreasing of static recrystallized grain size. Based on the experimental data, an equation for the static recrystallized grain size was derived using the least square method. The grain sizes calculated using this equation fit well with the measured ones compared with the equations for fine-grained austenite and for coarse-grained austenite of Nb-V microalloyed steel.

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

    Science.gov (United States)

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

    2009-01-01

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

  16. 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.

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

    Science.gov (United States)

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

    2017-12-01

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

  18. Study of Radon and Thoron exhalation from soil samples of different grain sizes.

    Science.gov (United States)

    Chitra, N; Danalakshmi, B; Supriya, D; Vijayalakshmi, I; Sundar, S Bala; Sivasubramanian, K; Baskaran, R; Jose, M T

    2018-03-01

    The exhalation of radon ( 222 Rn) and thoron ( 220 Rn) from a porous matrix depends on the emanation of them from the grains by the recoil effect. The emanation factor is a quantitative estimate of the emanation phenomenon. The present study is to investigate the effect of grain size of the soil matrix on the emanation factor. Soil samples from three different locations were fractionated into different grain size categories ranging from <0.1 to 2mm. The emanation factors of each of the grain size range were estimated by measuring the mass exhalation rates of radon and thoron and the activity concentrations of 226 Ra and 232 Th. The emanation factor was found to increase with decrease in grain size. This effect was made evident by keeping the parent radium concentration constant for all grain size fractions. The governing factor is the specific surface area of the soil samples which increases with decrease in grain size. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2005-10-15

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

  20. 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.

  1. 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.

  2. Rock Magnetic and Grain Size Variation Along A 50m Cretaceous Sedimentary Section of The Marilia Formation (bauru Basin), Brazil

    Science.gov (United States)

    Tamrat, E.; Ernesto, M.; Watanabe, J.; Saad, A. R.; Fulfaro, V. J.

    We present a detailed rock magnetic investigation of a sedimentary section from the Marilia Formation of the Bauru Basin (22.22S, 49.96W), Brasil. Sampling was con- ducted over 0.5m interval of a 50m Late Cretaceous sedimentary deposit. The deposits are consists of coarse to conglomeratic sandstones with abundant calciferous cement and nodules. A total of 81 samples from 67 sites have carried out using hysteresis loop and thermomagnetic curves in order to identify the magnetic mineral and distribution of their grain-size. Trends in rock magnetic parameters with remanent saturation be- low 300mT and moderate coercivity of remanence are consistent with a contribution of Pseudo-single domain to small Multi-domain magnetite. High temperature exper- iments of the magnetic susceptibility up to 700C indicate abundant magnetite with minor contribution of titanomaghemite. Changes in hysteresis parameters are consis- tent with changes in the relative amounts of the different magnetite size fractions. On the basis of rock magnetic investigation, a sample of the Marilia Formation appears to be a reliable recorder of the geomagnetic field during sediment deposition. Their straightforward mineralogy and minimal changes in magnetic concentration consti- tute an opportunity to examine not only rock magnetic and grain size variation, but directional changes and magnetostratigraphy data as well.

  3. Modeling grain size variations of aeolian gypsum deposits at White Sands, New Mexico, using AVIRIS imagery

    Science.gov (United States)

    Ghrefat, H.A.; Goodell, P.C.; Hubbard, B.E.; Langford, R.P.; Aldouri, R.E.

    2007-01-01

    Visible and Near-Infrared (VNIR) through Short Wavelength Infrared (SWIR) (0.4-2.5????m) AVIRIS data, along with laboratory spectral measurements and analyses of field samples, were used to characterize grain size variations in aeolian gypsum deposits across barchan-transverse, parabolic, and barchan dunes at White Sands, New Mexico, USA. All field samples contained a mineralogy of ?????100% gypsum. In order to document grain size variations at White Sands, surficial gypsum samples were collected along three Transects parallel to the prevailing downwind direction. Grain size analyses were carried out on the samples by sieving them into seven size fractions ranging from 45 to 621????m, which were subjected to spectral measurements. Absorption band depths of the size fractions were determined after applying an automated continuum-removal procedure to each spectrum. Then, the relationship between absorption band depth and gypsum size fraction was established using a linear regression. Three software processing steps were carried out to measure the grain size variations of gypsum in the Dune Area using AVIRIS data. AVIRIS mapping results, field work and laboratory analysis all show that the interdune areas have lower absorption band depth values and consist of finer grained gypsum deposits. In contrast, the dune crest areas have higher absorption band depth values and consist of coarser grained gypsum deposits. Based on laboratory estimates, a representative barchan-transverse dune (Transect 1) has a mean grain size of 1.16 ??{symbol} (449????m). The error bar results show that the error ranges from - 50 to + 50????m. Mean grain size for a representative parabolic dune (Transect 2) is 1.51 ??{symbol} (352????m), and 1.52 ??{symbol} (347????m) for a representative barchan dune (Transect 3). T-test results confirm that there are differences in the grain size distributions between barchan and parabolic dunes and between interdune and dune crest areas. The t-test results

  4. Tungsten Carbide Grain Size Computation for WC-Co Dissimilar Welds

    Science.gov (United States)

    Zhou, Dongran; Cui, Haichao; Xu, Peiquan; Lu, Fenggui

    2016-06-01

    A "two-step" image processing method based on electron backscatter diffraction in scanning electron microscopy was used to compute the tungsten carbide (WC) grain size distribution for tungsten inert gas (TIG) welds and laser welds. Twenty-four images were collected on randomly set fields per sample located at the top, middle, and bottom of a cross-sectional micrograph. Each field contained 500 to 1500 WC grains. The images were recognized through clustering-based image segmentation and WC grain growth recognition. According to the WC grain size computation and experiments, a simple WC-WC interaction model was developed to explain the WC dissolution, grain growth, and aggregation in welded joints. The WC-WC interaction and blunt corners were characterized using scanning and transmission electron microscopy. The WC grain size distribution and the effects of heat input E on grain size distribution for the laser samples were discussed. The results indicate that (1) the grain size distribution follows a Gaussian distribution. Grain sizes at the top of the weld were larger than those near the middle and weld root because of power attenuation. (2) Significant WC grain growth occurred during welding as observed in the as-welded micrographs. The average grain size was 11.47 μm in the TIG samples, which was much larger than that in base metal 1 (BM1 2.13 μm). The grain size distribution curves for the TIG samples revealed a broad particle size distribution without fine grains. The average grain size (1.59 μm) in laser samples was larger than that in base metal 2 (BM2 1.01 μm). (3) WC-WC interaction exhibited complex plane, edge, and blunt corner characteristics during grain growth. A WC ( { 1 {bar{{1}}}00} ) to WC ( {0 1 1 {bar{{0}}}} ) edge disappeared and became a blunt plane WC ( { 10 1 {bar{{0}}}} ) , several grains with two- or three-sided planes and edges disappeared into a multi-edge, and a WC-WC merged.

  5. 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.

  6. The Effect of Grain Size on the Strain Hardening Behavior for Extruded ZK61 Magnesium Alloy

    Science.gov (United States)

    Zhang, Lixin; Zhang, Wencong; Chen, Wenzhen; Duan, Junpeng; Wang, Wenke; Wang, Erde

    2017-12-01

    The effects of grain size on the tensile and compressive strain hardening behaviors for extruded ZK61 alloys have been investigated by uniaxial tensile and compressive tests along the extrusion directions. Cylindrical tension and compression specimens of extruded ZK61 alloys with various sized grain were fabricated by annealing treatments. Tensile and compressive tests at ambient temperature were conducted at a strain rate of 0.5 × 10-3 s-1. The results indicate that both tensile strain hardening and compressive strain hardening of ZK61 alloys with different grain sizes have an athermal regime of dislocation accumulation in early deformation. The threshold stress value caused dynamic recovery is predominantly related to grain size in tensile strain hardening, but the threshold stress values for different grain sizes are almost identical in compressive strain hardening. There are obvious transition points on the tensile strain hardening curves which indicate the occurrence of dynamic recrystallization (DRX). The tensile strain hardening rate of the coarse-grained alloy obviously decreases faster than that of fine-grained alloys before DRX and the tensile strain hardening curves of different grain sizes basically tend to parallel after DRX. The compressive strain hardening rate of the fine-grained alloy obviously increases faster than that of coarse-grained alloy for twin-induced strain hardening, but compressive strain hardening curves also tend to parallel after twinning is exhausted.

  7. Surface Characterization and Grain Size Calculation of Silver Films Deposited by Thermal Evaporation

    Science.gov (United States)

    Maqbool, Muhammad; Khan, Tahirzeb

    Thin films of pure silver were deposited on glass substrate by thermal evaporation process at room temperature. Surface characterization of the films was performed using X-ray diffraction (XRD) and Atomic Force Microscopy (AFM). Thickness of the films varied between 20 nm and 60 nm. XRD analysis provided a sharp peak at 38.75° from silver. These results indicated that the films deposited on glass substrates at room temperature are crystalline. 3D and top view pictures of the films were obtained by AFM to study the grain size and its dependency on various factors. Grain sizes were calculated using the XRD results and Scherer's formula. Average grain size increased with the thickness of the deposited films. A minimum grain size of 8 nm was obtained for 20 nm thick films, reaching a maximum value of 41.9 nm when the film size reaches 60 nm. We could not find any sequential variation in the grain size with the growth rate.

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

    Science.gov (United States)

    Becton, Matthew; Wang, Xianqiao

    2015-09-14

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

  9. 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.

  10. Small grain size zirconium-based coatings deposited by magnetron sputtering at low temperatures

    International Nuclear Information System (INIS)

    Jimenez, O.; Audronis, M.; Leyland, A.; Flores, M.; Rodriguez, E.; Kanakis, K.; Matthews, A.

    2015-01-01

    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 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 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.

  11. 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.

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

    Science.gov (United States)

    Efthimiadis, K. G.; Ntallis, N.

    2018-02-01

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

  13. Grain size distribution and heat conductivity of copper processed by equal channel angular pressing

    International Nuclear Information System (INIS)

    Gendelman, O.V.; Shapiro, M.; Estrin, Y.; Hellmig, R.J.; Lekhtmakher, S.

    2006-01-01

    We report the results of measurements of the grain size distribution function and the thermal conductivity of ultrafine-grained copper produced by equal channel angular pressing (ECAP), with special attention to the evolution of these quantities with the number of pressing cycles. To explain the experimental findings, the equilibrium grain size distribution function (GSDF) evolving during ECAP has been calculated on the basis of a simplified theoretical model. The model involves a single unknown physical parameter-the most probable grain size. With this parameter fitted to the experimental data the calculated GSDF fairly closely reproduces the experimental data. A model for thermal conductivity of ECAP processed copper has been proposed, which relates thermal conductivity to the GSDF parameters and the coefficient of electron reflection at grain boundaries

  14. 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.

  15. 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.

  16. Grain size effect on transferability in micro-coining process assisted by ultrasonic vibration

    Directory of Open Access Journals (Sweden)

    Shimizu Tetsuhide

    2015-01-01

    Full Text Available The present study reports the assisting effect by the ultrasonic vibration in a micro-coining process. Particularly, we were focused on the grain size of the work material to study the scale dependency of transferability under the assistance of ultrasonic vibration. The pure copper plate of 0.3 mm in thickness was used as the working material. The micro-coining process was performed on the specimens with three different grain sizes which were obtained through an annealing process. The result showed that the vibration assisted effect on transferability becomes more significant for the material with larger grain sizes. Assisting effect of ultrasonic vibration for the coarse grained materials is also demonstrated.

  17. The equivalent dose comparison of different grain size quartz from lakeshore sediments in the arid region

    International Nuclear Information System (INIS)

    Fan Yuxin; Chen Fahu; Zhao Hui

    2009-01-01

    To investigate the feasibility of OSL dating of lakeshore sediments, equivalent dose (D e ) values of quartz fractions in different grain-size were measured using the 'Double-SAR' protocol of optical dating in four lakeshore sediments. There are two obvious different relations between D e values and grain sizes. The first situation is that the D e values are accordant with each other for fractions between 63 μm and 400 μm with a slightly decreasing tread of D e values as increasing of grain-size. The second situation is that the D e values are accordant to each other for fractions between 125 μm and 300 μm, while the D e values of the 63-90 μm fraction are obviously smaller than others. The first is consistent with those reported elsewhere, while the second can't be understood by the previous theory. (authors)

  18. 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.

  19. 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

  20. 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

  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. 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).

  3. 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.

  4. 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).

  5. 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

  6. 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

  7. 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

  8. 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.

  9. 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 ...

  10. 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

  11. Effects of grain size distribution on the packing fraction and shear strength of frictionless disk packings

    Science.gov (United States)

    Estrada, Nicolas

    2016-12-01

    Using discrete element methods, the effects of the grain size distribution on the density and the shear strength of frictionless disk packings are analyzed. Specifically, two recent findings on the relationship between the system's grain size distribution and its rheology are revisited, and their validity is tested across a broader range of distributions than what has been used in previous studies. First, the effects of the distribution on the solid fraction are explored. It is found that the distribution that produces the densest packing is not the uniform distribution by volume fractions as suggested in a recent publication. In fact, the maximal packing fraction is obtained when the grading curve follows a power law with an exponent close to 0.5 as suggested by Fuller and Thompson in 1907 and 1919 [Trans Am. Soc. Civ. Eng. 59, 1 (1907) and A Treatise on Concrete, Plain and Reinforced (1919), respectively] while studying mixtures of cement and stone aggregates. Second, the effects of the distribution on the shear strength are analyzed. It is confirmed that these systems exhibit a small shear strength, even if composed of frictionless particles as has been shown recently in several works. It is also found that this shear strength is independent of the grain size distribution. This counterintuitive result has previously been shown for the uniform distribution by volume fractions. In this paper, it is shown that this observation keeps true for different shapes of the grain size distribution.

  12. Discrimination of sediment provenance in the Yellow Sea: Secondary grain-size effect and REE proxy

    Science.gov (United States)

    Jung, Hoi-Soo; Lim, Dhongil; Jeong, Do-Hyun; Xu, Zhaokai; Li, Tiegang

    2016-06-01

    This study analyzed grain size and elemental concentrations (Al, Mg, Fe, and rare earth elements (REEs)) in 91 surface sediments to elucidate sediment provenance in the Yellow Sea. Elemental concentrations were normalized by Al concentration (Celement/CAl) to minimize the sediment grain-size effect (GSE). However, noticeable linear relationships between Al concentration (or mean grain size) and the ratio (e.g., Mg/Al or Fe/Al) appeared unexpectedly in pair diagrams. The spatial distribution patterns of Fe/Al and Mg/Al ratios were also similar to the pattern of mean grain size. This implies that the GSE was not removed completely, even after the normalization process. Thus, great care must be taken when applying the ratios of Celement/CAl as a proxy of sediment provenance. To improve provenance discrimination of the sediments in the Yellow Sea, the difference between the REE distribution patterns of Chinese and Korean river sediments, expressed as δ (δ = REE∗(La) - REE∗(Lu)), was calculated, and the spatial distribution patterns of the δ values were mapped. The δ values gradually increased from the western to the eastern part of the Yellow Sea, except for low δ values in the southeastern part of the Yellow Sea. This result indicates that the majority of Chinese and Korean river sediments are accumulating near to their respective coasts, except for a deposit along the southwestern coast of Korea in which a considerable amount of sediment from Chinese rivers has been accumulating.

  13. Anisotropic Grain Size Estimation Using Computer Simulations and w-s diagram

    Czech Academy of Sciences Publication Activity Database

    Ponížil, P.; Procházka, J.; Čermák, R.; Saxl, Ivan

    2005-01-01

    Roč. 4, č. 7 (2005), s. 728-735 ISSN 1109-2750 R&D Projects: GA ČR(CZ) GA201/03/0946 Institutional research plan: CEZ:AV0Z10190503 Keywords : grain size estimation * anisotropic material * tessellation Subject RIV: BB - Applied Statistics, Operational Research

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

    DEFF Research Database (Denmark)

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

    2001-01-01

    In the chalk of the Ekofisk formation in the Chalk Group of the North Sea, substantial depth-related variations in porosityare observed. With the aim of obtaining a textural interpretation of these porositydata, we have developed a method to assess the grain size distribution of the chalk from...

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

    African Journals Online (AJOL)

    user

    deviation from linear proportionality between flow stress and grain size in austenitic steels. This influence ... phases [12]. Delta ferrite contributes to the flow stress as well as t9 the tensile strength of austenitic steels. [13,14] However, for Cr-Ni-Mn steels, there is little information ... 1173K and 1473K or two hours followed by.

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

    NARCIS (Netherlands)

    Niemeijer, André; Elsworth, Derek; Marone, Chris

    2009-01-01

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

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

    NARCIS (Netherlands)

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

    1993-01-01

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

  18. 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

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

    African Journals Online (AJOL)

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

  20. 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

  1. Grain-size-independent plastic flow at ultrahigh pressures and strain rates.

    Science.gov (United States)

    Park, H-S; Rudd, R E; Cavallo, R M; Barton, N R; Arsenlis, A; Belof, J L; Blobaum, K J M; El-dasher, B S; Florando, J N; Huntington, C M; Maddox, B R; May, M J; Plechaty, C; Prisbrey, S T; Remington, B A; Wallace, R J; Wehrenberg, C E; Wilson, M J; Comley, A J; Giraldez, E; Nikroo, A; Farrell, M; Randall, G; Gray, G T

    2015-02-13

    A basic tenet of material science is that the flow stress of a metal increases as its grain size decreases, an effect described by the Hall-Petch relation. This relation is used extensively in material design to optimize the hardness, durability, survivability, and ductility of structural metals. This Letter reports experimental results in a new regime of high pressures and strain rates that challenge this basic tenet of mechanical metallurgy. We report measurements of the plastic flow of the model body-centered-cubic metal tantalum made under conditions of high pressure (>100  GPa) and strain rate (∼10(7)  s(-1)) achieved by using the Omega laser. Under these unique plastic deformation ("flow") conditions, the effect of grain size is found to be negligible for grain sizes >0.25  μm sizes. A multiscale model of the plastic flow suggests that pressure and strain rate hardening dominate over the grain-size effects. Theoretical estimates, based on grain compatibility and geometrically necessary dislocations, corroborate this conclusion.

  2. The recrystallized grain size piezometer for quartz: An EBSD-based calibration

    Science.gov (United States)

    Cross, A. J.; Prior, D. J.; Stipp, M.; Kidder, S.

    2017-07-01

    We have reanalyzed samples previously used for a quartz recrystallized grain size paleopiezometer, using electron backscatter diffraction (EBSD). Recrystallized and relict grains are separated using their grain orientation spread, which acts as a measure of intragranular lattice distortion and a proxy for dislocation density. For EBSD maps made with a 1 μm step size, the piezometer relationship is D = 103.91 ± 0.41 • σ-1.41 ± 0.21 (for root-mean-square mean diameter values). We also present a "sliding resolution" piezometer relationship, D = 104.22 ± 0.51 • σ-1.59 ± 0.26, that combines 1 μm step size data at coarser grain sizes with 200 nm step size data at finer grain sizes. The sliding resolution piezometer more accurately estimates stress in fine-grained (<10 μm) samples. The two calibrations give results within 10% of each other for recrystallized grain sizes between 10 μm and 100 μm. Both piezometers match the original light optical microscopy quartz piezometer within error.

  3. 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.

  4. Effects of grain size on the spallation behavior of pure copper under plate-impact loading

    Directory of Open Access Journals (Sweden)

    Jiang ZhaoXiu

    2015-01-01

    Full Text Available The effects of grain size on the dynamic tensile fracture (or spall response were investigated for high purity copper materials by plate-impact experiments. The spall strength estimated from the free surface velocity profile is nearly constant with no significant effect from the grain size. However, differences are observed in the acceleration rate of velocity rebound beyond the minima. This may be attributed to the effect of grain size on the growth rate of damage. Metallographic analyses of the fracture surface show that the characteristic feature of the fracture surface clearly depends on the grain size. In the smaller samples, the fracture surfaces are decorated with large, high-density ductile dimples suggesting that the preferential failure mode is ductile intergranular fracture. In the larger samples, the fracture surfaces have a rock candy appearance with small, brittle, high density dimples as well as large ductile dimples suggesting that the fracture mode is a mix of both brittle intergranular fracture and ductile transgranular fracture.

  5. Grain size effect on electrical resistivity of bulk nanograined Bi2Te3 material

    International Nuclear Information System (INIS)

    Ivanov, Oleg; Maradudina, Oxana; Lyubushkin, Roman

    2015-01-01

    The bulk nanograined Bi 2 Te 3 material with various mean grain sizes changing from ~ 97 nm to ~ 51 nm was prepared by microwave assisted solvothermal method and hot pseudo-isostatic pressure. It was found that the specific electrical resistivity of the material increases as mean grain size decreases. Such kind of the grain effect on the resistivity can be attributed to enhanced electron scattering at the grain boundaries. The Mayadas–Shatzkes model was applied to explain experimental results. In this model the grain boundaries are regarded as potential barriers which have to be overcome by the electrons. The reflectivity R of the grain boundaries for the material under study was estimated to be equal to ~ 0.7. - Highlights: • The bulk nanograined Bi 2 Te 3 material with various mean grain sizes was prepared. • It was found that the electrical resistivity of the material increases as grain size decreases. • The Mayadas–Shatzkes model was applied to explain experimental results. • The reflectivity R of the grain boundaries was estimated to be equal to ~ 0.7

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

    African Journals Online (AJOL)

    PROF EKWUEME

    along the beaches are hence a result of complex interaction between sediment source, wave energy level and the general offshore slope on which the beach is constructed. The intensity of the wave action in the littoral zone generally redeposits and sort materials of all grain sizes. Thus, the composition of beach sediment is.

  7. 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.

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

    CSIR Research Space (South Africa)

    Milman, YV

    1999-01-01

    Full Text Available , grain size and cobalt content on the hardness of WC?Co alloys Yu.V. Milman a, S. Luyckx b,c, IT Northrop d a Institute of Problems in Materials Science, Kiev, Ukraine b School of Process and Materials Engineering, University of the Witwatersrand...

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

    Indian Academy of Sciences (India)

    Administrator

    Grain-size effects on thermal properties of BaTiO3 ceramics. C J XIAO*, Z X LI and X R DENG. Department of Materials Science and Engineering, Henan University of Technology, Zhengzhou, China. MS received 5 January 2010. Abstract. Dense nanocrystalline BaTiO3 ceramics are successfully prepared by the high ...

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

    NARCIS (Netherlands)

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

    1998-01-01

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

  11. 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.

  12. 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)...

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

    CSIR Research Space (South Africa)

    Burns, J

    2017-05-01

    Full Text Available sediment grain size on beaches in False Bay James Burns (MSc) Melanie Lück-Vogel CSIR | Stellenbosch University 1 ISRSE-37 Symposium – Tshwane Wednesday 10 May 2017 Kogel Bay (SA) Strand (SA) Strand (SA) The coastal zone is an important asset...

  14. 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

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

    Energy Technology Data Exchange (ETDEWEB)

    Marques, A.P. [ITN - Instituto Tecnologico e Nuclear, 2686-953 Sacavem (Portugal)]. E-mail: amarques@itn.pt; Freitas, M.C. [ITN - Instituto Tecnologico e Nuclear, 2686-953 Sacavem (Portugal); Wolterbeek, H.Th. [IRI - TU Delft, Mekelweg 15, 2629 JB Delft (Netherlands); Verburg, T.G. [IRI - TU Delft, Mekelweg 15, 2629 JB Delft (Netherlands); Goeij, J.J.M. de [IRI - TU Delft, Mekelweg 15, 2629 JB Delft (Netherlands)

    2007-02-15

    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 {mu}m) was ground and sieved through nylon nets with 64 {mu}m, 41 {mu}m and 20 {mu}m 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.

  16. 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

  17. 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.

  18. 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.

  19. Can a grain size-dependent viscosity help yielding realistic seismic velocities of LLSVPs?

    Science.gov (United States)

    Schierjott, J.; Cheng, K. W.; Rozel, A.; Tackley, P. J.

    2017-12-01

    Seismic studies show two antipodal regions of low shear velocity at the core-mantle boundary (CMB), one beneath the Pacific and one beneath Africa. These regions, called Large Low Shear Velocity Provinces (LLSVPs), are thought to be thermally and chemically distinct and thus have a different density and viscosity. Whereas there is some general consensus about the density of the LLSVPs the viscosity is still a very debated topic. So far, in numerical studies the viscosity is treated as either depth- and/or temperature- dependent but the potential grain size- dependence of the viscosity is neglected most of the time. In this study we use a self-consistent convection model which includes a grain size- dependent rheology based on the approach by Rozel et al. (2011) and Rozel (2012). Further, we consider a primordial layer and a time-dependent basalt production at the surface to dynamically form the present-day chemical heterogeneities, similar to earlier studies, e.g by Nakagawa & Tackley (2014). With this model we perform a parameter study which includes different densities and viscosities of the imposed primordial layer. We detect possible thermochemical piles based on different criterions, compute their average effective viscosity, density, rheology and grain size and investigate which detecting criterion yields the most realistic results. Our preliminary results show that a higher density and/or viscosity of the piles is needed to keep them at the core-mantle boundary (CMB). Relatively to the ambient mantle grain size is high in the piles but due to the temperature at the CMB the viscosity is not remarkably different than the one of ordinary plumes. We observe that grain size is lower if the density of the LLSVP is lower than the one of our MORB material. In that case the average temperature of the LLSVP is also reduced. Interestingly, changing the reference viscosity is responsible for a change in the average viscosity of the LLSVP but not for a different average

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

    NARCIS (Netherlands)

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

    2013-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-03-01

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

  2. 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.

  3. 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

  4. 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.

  5. 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.

  6. 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

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

    DEFF Research Database (Denmark)

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

    2017-01-01

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

  8. 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.)

  9. Grain size effect on martensitic transformation behavior in Fe-Ni invar alloys

    Energy Technology Data Exchange (ETDEWEB)

    Aikawa, Yoshikazu [Metal Powder Manufacturing and Sales Division, Sanyo Special Steel Co., Ltd, 3007 Nakashima, Shikama-ku, Himeji 672-8677 (Japan); Terai, Tomoyuki; Kakeshita, Tomoyuki [Department of Material Science and Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871 (Japan)

    2009-05-01

    We investigated the grain size effect on martensitic transformation behavior in Fe-30at.%Ni powder and ribbon specimens. The powder specimen with a particle size of 5 um does not show an athermal martensitic transformation but does show an isothermal martensitic transformation after an incubation time of about 10{sup 4} s at 205 K. On the other hand, the powder specimen with a particle size of 20 um shows an athermal martensitic transformation at 150 K. The value of M{sub s} is much lower than that of the single crystal and of bulk specimens. However, the M{sub s} temperature of a ribbon specimen with an average grain size of 15 um is found to be almost identical to that of the single crystal and of bulk specimens. Considering these results, the athermal martensitic transformation is suppressed by the decrease in particle size if grains do not have grain boundaries.

  10. Grain size effect on martensitic transformation behavior in Fe-Ni invar alloys

    Science.gov (United States)

    Aikawa, Yoshikazu; Terai, Tomoyuki; Kakeshita, Tomoyuki

    2009-05-01

    We investigated the grain size effect on martensitic transformation behavior in Fe-30at.%Ni powder and ribbon specimens. The powder specimen with a particle size of 5 um does not show an athermal martensitic transformation but does show an isothermal martensitic transformation after an incubation time of about 104 s at 205 K. On the other hand, the powder specimen with a particle size of 20 um shows an athermal martensitic transformation at 150 K. The value of Ms is much lower than that of the single crystal and of bulk specimens. However, the Ms temperature of a ribbon specimen with an average grain size of 15 um is found to be almost identical to that of the single crystal and of bulk specimens. Considering these results, the athermal martensitic transformation is suppressed by the decrease in particle size if grains do not have grain boundaries.

  11. Effects of grain size on the quasi-static mechanical properties of ultrafine-grained and nanocrystalline tantalum

    Science.gov (United States)

    Ligda, Jonathan Paul

    trend of increasing hardness with radial position that saturates at 4.5 GPa near the edge, and decreasing strain rate sensitivity. The micromechanical tests show two distinct regions on a processed circular disk, a non-shearing region and a shearing region. Microcompression/tension tests in the region of 1.0 5.3 mm show a drastic switch to localized plastic deformation in the form of shear bands, with evidence of grain rotation as the active deformation mechanism, and a measureable tension-compression asymmetry. Grains are elongated at all locations, and while the minimum diameters are consistent between regions, the elongated diameter in the shearing region is reduced. The transition to localized deformation is attributed to this reduced dimension. A larger percentage of grains in the shearing region have an elongated diameter below the critical grain size necessary to activate the grain rotation mechanism. The tension-compression asymmetry is due to an increased dependence on the normal stress for yielding, meaning NC Ta would follow a Mohr-Coulomb criterion over the traditional Tresca or von Mises.

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

    OpenAIRE

    H. S. Negi; A. Kokhanovsky

    2010-01-01

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

  13. Effect of Coal Grain Size on Sorption Capacity with Respect to Propylene and Acetylene

    Directory of Open Access Journals (Sweden)

    Agnieszka Dudzińska

    2017-11-01

    Full Text Available Propylene and acetylene are released to mine air with the increase in the temperature of self-heating coal. Concentrations of these gases in mine air are applied as indicators of the progress of the self-heating process. Hydrocarbons emitted from the self-ignition center are sorbed on coal, while migrating through the mine workings. Coal crushed during the mining process is characterized by a high sorption capacity, which facilitates the sorption phenomena. This results in the decrease in hydrocarbons content in mine air, and in the subsequent incorrect assessment of the development of the self-heating process. The results of the experimental study on propylene and acetylene sorption on Polish coals acquired from operating coal mines are presented in this paper. Bituminous coal is characterized by a high sorption capacity with respect to unsaturated hydrocarbons, like propylene and acetylene. The sorbed volumes depend on the grade of metamorphism, porosity, and chemical characteristics of coal. Low level of metamorphism, increased porosity, and oxygen content result in higher sorption capacity of coals. The reduction in grain size of coals also results in the increased sorption capacity with respect to hydrocarbons. The most significant increase in the volumes of sorbed propylene and acetylene with the decrease in grain class was observed for coals of low porosity, high grade of metamorphism, and low to medium sorption capacities. The 10-fold decrease in coal grain size resulted in the 3 to 6-fold increase in the volume of sorbed propylene, and 2-fold increase for acetylene. The decrease in grain size results in higher accessibility of pore structure, increased pore volume and area, and higher number of active centers interacting with hydrocarbons of dipole characteristics. For coals with low grade metamorphism, high porosity, and high sorption capacity the volumes of sorbed propylene and acetylene increased only slightly with the decrease in

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

    Science.gov (United States)

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

    2017-01-01

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

  15. 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 ...

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

    Science.gov (United States)

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

    2017-04-01

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

  17. 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...

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

    DEFF Research Database (Denmark)

    Hansen, Niels

    1977-01-01

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

  19. Model for evolution of grain size in the rim region of high burnup UO2 fuel

    Science.gov (United States)

    Xiao, Hongxing; Long, Chongsheng; Chen, Hongsheng

    2016-04-01

    The restructuring process of the high burnup structure (HBS) formation in UO2 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 UO2 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 UO2 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.

  20. 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.

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

    Directory of Open Access Journals (Sweden)

    B. Simons

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

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  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 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.

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

    Directory of Open Access Journals (Sweden)

    R. Heilbronner

    2017-10-01

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

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

    Science.gov (United States)

    Heilbronner, Renée; Kilian, Rüdiger

    2017-10-01

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

  11. Thinning behavior of laminated sheets metal in warm deep-drawing process under various grain sizes

    Directory of Open Access Journals (Sweden)

    Kadkhodayan Mehran

    2016-01-01

    Full Text Available The purpose of present research is to investigate the thickness distribution on the warm deep-drawing process of laminated sheets consisting of aluminum alloy series 1050, 5052 and stainless steel 304 (SUS, experimentally. Individually for each layer, the influences of blank temperature and grain size on thinning behavior are clearly demonstrated. In order to survey the thinning behavior in laminate sheet behavior during warm deep-drawing process; three blank temperatures namely, 25° C, 100° C and 160° C are examined. Moreover, to obtain different grain sizes, the aluminium sheets are annealed at 350° C, 400° C and 450° C for 1 hour. Results indicate that increasing temperature and grain size lead to maximum thinning in all layers in Al 1050/SUS and Al 5052/SUS specimens increase. In addition, the most susceptible zone to fracture in aluminum sheets (Al 1050 and Al 5052 is punch profile radius region; nevertheless, for stainless steel sheets this zone switch to central zone of formed cup. These can be attributed to the fact that the adhesive layer play a crucial role in thickness distribution of steel 304 layer, therefore the distribution of thickness strain for adhesive layer is also investigated.

  12. 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 (Stream sediments located near the Åland sill, more than 850 km upstream from the terminal moraines. This result is in agreement with both numerical modeling and geomorphological 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.

  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

    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.

  15. 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.

  16. Problems during the determination of grain-sizes in austenitic plates by the application of ultrasonic-backscattering

    International Nuclear Information System (INIS)

    Hecht, A.; Neumann, E.; Mundry, E.; Thiel, R.

    1980-01-01

    Ultrasonic backscattering makes possible the nondestructive determination of grain size in austenitic strips. In immersion technique a short pulse is sent into the material and the backscattered sound-amplitude is measured. When using a calibration curve, grain sizes can be calculated from the backscattered sound-amplitudes. There are problems in practical use because of mechanical and electronical data having an influence on the results of measurement. An exact determination of grain size depends on accurate mechanical adjustment and on stability of the electronical equipment, too. (orig.) [de

  17. Crack Propagation Behavior of Alumina with Different Grain Sizes under Static and Cyclic Fatigue

    Science.gov (United States)

    El Attaoui, H.; Saadaoui, M.; Chevalier, J.; Fantozzi, G.

    Crack propagation in high purity alumina ceramics with different grain sizes was investigated with the Double Torsion method during static and cyclic fatigue. Slow crack growth in alumina is due to stress corrosion by water molecules at the crack tip. However, the microstructure plays a significant role on V-KI laws (crack velocity versus stress intensity factor) under static loading: the higher the grain size, the larger the crack resistance. This increase in crack resistance with grain size is easily attributed to crack bridging mechanisms. A compliance function, based on the variation of compliance with bridging stresses, is applied here to quantify the amount of crack bridging. It is shown experimentally that the reinforcement due to crack bridging is proportional to the compliance function. Under cyclic fatigue, a reduction of crack bridging is observed, followed by a decrease of the compliance function. During crack propagation under cyclic loading, the compliance is affected by the frictional degradation of bridges (due to repeated unloading and loading). The amount of frictional degradation versus number of cycles is followed for different loading conditions. At low loads, the crack rate is initially equal to zero, but crack bridging decreases monotonically with the number of cycles. After an 'incubation' period, crack propagation initiates and new bridges are formed. This leads further to an equilibrium between crack shielding degradation and crack shielding accumulation. The equilibrium condition is obtained more rapidly for higher loads. In any case, the crack resistance at the equilibrium is always lower than that obtained under monotonic loading. This is particularly significant for coarse grain microstructures: the higher the crack resistance under monotonic loading, the higher the degradation under cyclic loading. This implies, that it is inappropriate to incorporate directly V-KI curves obtained from monotonic loading into a cyclic fatigue analysis

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

    Science.gov (United States)

    Chiang, Chien-Hung; Wu, Chun-Guey

    2016-09-22

    The power conversion efficiency (PCE) of the perovskite solar cell is high enough to be commercially viable. The next important issue is the stability of the device. This article discusses the effect of the perovskite grain-size on the long-term stability of inverted perovskite solar cells. Perovskite films composed of various sizes of grains were prepared by controlling the solvent annealing time. The grain-size related stability of the inverted cells was investigated both in ambient atmosphere at relative humidity of approximately 30-40 % and in a nitrogen filled glove box (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.

  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. Extending and simplifying the standard Köhn-pipette technique for grain size analysis

    Science.gov (United States)

    Hirsch, Florian; Raab, Thomas

    2014-05-01

    Grain size distribution is a fundamental parameter to characterize physical properties of soils and sediments. Manifold approaches exist and according to the DIN ISO 11277 soil texture is analyzed by default with the combined pipette sieving and sedimentation method developed by Köhn. With this standard technique subfractions of sand and silt as well as the total clay content can be determined but the differentiation of clay subfractions is impossible. As the differentiation of the clay subfractions yields relevant information about pedogenesis, we present a protocol basing on standard techniques of granulometry with easy to handle and low cost equipment. The protocol was tested on a set of soil samples to cover the range of grain size distributions. We used a three-step procedure for achieving the grain size distribution of soil samples taking into account the subfractions of sand, silt and clay by a combination of sedimentation, centrifugal sedimentation and wet sieving. The pipetting was done with a piston-stroke pipette instead of the referred complex pipette from the DIN ISO 11277. Our first results show that the applied protocol is less prone to operating errors than the standard Köhn-pipette technique. Furthermore, even a less experienced laboratory worker can handle 10 samples in one day. Analyses of a luvisol profile, sampled in high spatial resolution, showed that the lessivation process is characterized by translocation of fine clay from the eluvial horizon to the illuvial horizon. Therefore our protocol is a fast alternative to detect lessivation, which is otherwise only clearly identifiable by micromorphological investigation and not by the standard Köhn-pipette technique.

  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. Orthographic consistency affects spoken word recognition at different grain-sizes

    DEFF Research Database (Denmark)

    Dich, Nadya

    2014-01-01

    A number of previous studies found that the consistency of sound-to-spelling mappings (feedback consistency) affects spoken word recognition. In auditory lexical decision experiments, words that can only be spelled one way are recognized faster than words with multiple potential spellings. Previous.......g., lobe) faster than words with consistent rhymes where the vowel has a less typical spelling (e.g., loaf). The present study extends previous literature by showing that auditory word recognition is affected by orthographic regularities at different grain sizes, just like written word recognition...... and spelling. The theoretical and methodological implications for future research in spoken word recognition are discussed....

  4. 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.)

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

    Science.gov (United States)

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

    2018-02-01

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

  6. A Genetic Based Neuro Fuzzy Technique for Process Grain Sized Scheduling of Parallel Jobs

    OpenAIRE

    Keppanagowder Thanushkodi; Sadasivam V. Sudha

    2012-01-01

    Problem statement: In this study, we present the development of genetic algorithm based neuro fuzzy technique for process grain sized in scheduling of parallel jobs with the help of real lIfe workload data. Approach: The study uses the rule based scheduling strategy for the scheduling and classIfies all possible scheduling strategies. The rule bases are developed with the help of the neuro fuzzy system and with the genetic fuzzy system. From the comparison of the two classIfiers of the fuzzy ...

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

    DEFF Research Database (Denmark)

    Hansen, Niels; Ralph, B.

    1982-01-01

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

  8. 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

  9. 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...

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

    Science.gov (United States)

    Mulyukova, Elvira; Bercovici, David

    2018-02-01

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

  11. 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.

  12. Debris flow grain size scales with sea surface temperature over glacial-interglacial timescales

    Science.gov (United States)

    D'Arcy, Mitch; Roda Boluda, Duna C.; Whittaker, Alexander C.; Araújo, João Paulo C.

    2015-04-01

    Debris flows are common erosional processes responsible for a large volume of sediment transfer across a range of landscapes from arid settings to the tropics. They are also significant natural hazards in populated areas. However, we lack a clear set of debris flow transport laws, meaning that: (i) debris flows remain largely neglected by landscape evolution models; (ii) we do not understand the sensitivity of debris flow systems to past or future climate changes; and (iii) it remains unclear how to interpret debris flow stratigraphy and sedimentology, for example whether their deposits record information about past tectonics or palaeoclimate. Here, we take a grain size approach to characterising debris flow deposits from 35 well-dated alluvial fan surfaces in Owens Valley, California. We show that the average grain sizes of these granitic debris flow sediments precisely scales with sea surface temperature throughout the entire last glacial-interglacial cycle, increasing by ~ 7 % per 1 ° C of climate warming. We compare these data with similar debris flow systems in the Mediterranean (southern Italy) and the tropics (Rio de Janeiro, Brazil), and find equivalent signals over a total temperature range of ~ 14 ° C. In each area, debris flows are largely governed by rainfall intensity during triggering storms, which is known to increase exponentially with temperature. Therefore, we suggest that these debris flow systems are transporting predictably coarser-grained sediment in warmer, stormier conditions. This implies that debris flow sedimentology is governed by discharge thresholds and may be a sensitive proxy for past changes in rainfall intensity. Our findings show that debris flows are sensitive to climate changes over short timescales (≤ 104 years) and therefore highlight the importance of integrating hillslope processes into landscape evolution models, as well as providing new observational constraints to guide this. Finally, we comment on what grain size

  13. 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

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

    Data.gov (United States)

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

  15. 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.

  16. Influence of sieving time on the efficiency and accuracy of grain-size analysis of beach and dune sands

    OpenAIRE

    Román-Sierra, Jorge; Muñoz-Perez, Juan J.; Navarro-Pons, Marina

    2013-01-01

    Grain size is a fundamental property of sediments and is commonly used to describe sedimentary facies and classify sedimentary environments. Among the various conventional techniques utilized to determine grain-size frequency distributions, sieving is the most widely applied procedure. The accuracy of such analyses is, among other factors, strongly dependent on the sieving time. However, despite a substantial amount of research in this field, optimal sieving times for different types of sedim...

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

    Science.gov (United States)

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

    2017-01-01

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

  18. 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)

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

    Science.gov (United States)

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

    2011-07-15

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

  20. 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)

  1. 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.

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

    Science.gov (United States)

    Rosser, B. J.; O'Connor, M. D.

    2003-12-01

    The status of fish habitat in cold water streams in western North America has, by most accounts, been degraded significantly by sedimentation. In particular, land management activities induce erosion that contributes excess sand-size and finer sediment to stream systems, which is believed to have caused increases in the proportion of fine sediment in spawning gravels. Many watershed studies and regulatory programs have, drawing on previous scientific investigations, set thresholds for fine sediment concentrations in spawning beds. This study examines data from gravel bed streams collected with a McNeil sampler in northern California (typically 25 kg), as well as bulk sediment samples from the Waipaoa River in New Zealand (typically 50 kg). Confidence intervals for various percentiles of the grain size distributions were computed from these data using a two-stage sampling approach. Accuracy and precision of data from these sampling programs were considered in relation to the biological/regulatory thresholds as well as the effort required to obtain, process and analyze grain size distributions. Typically, very large samples are required to obtain data with high precision, suggesting that in many circumstances, it may be difficult to assess whether regulatory thresholds are exceeded.

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

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

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

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

    Science.gov (United States)

    Michaelides, K.

    2011-12-01

    Debris-mantled hillslopes are common in arid and semiarid environments where low rates of chemical weathering give rise to thin, non-cohesive soils mantled with a layer of coarse rock fragments derived from weathered bedrock that can reach boulder size. The grain size distributions (GSDs) on the surface of these hillslopes interact with different magnitudes and frequencies of runoff-producing rainfall events that selectively transport grain sizes of different classes depending on flow, grain position on the slope, and hillslope attributes. Sediment transport over many runoff events determines sediment delivery to the slope base, which ultimately modifies the GSD of valley floors. The relationship between hillslope attributes and sediment flux forms the basis of geomorphic transport laws used to model the topographic evolution of drainage basins over >104 y timescales, but the specific responses of sediment flux across the hillslope and the corresponding changes in GSDs to individual storm events are poorly understood. Sheetwash erosion of coarse fragments presents a particular set of conditions for sediment transport that is poorly resolved in current models. A particle-based model for sheetwash sediment transport on debris-mantled hillslopes was developed within a rainfall-runoff model. The rainfall-runoff model produces spatial values of flow depth and velocity which are used to drive a particle-by-particle force-balance model derived from first principles for grain sizes > 1 mm. Particles on the hillslope surface are represented explicitly and can be composed of mixed grain sizes of any distribution or of uniform sizes of any diameter. The model resolves all the forces on each particle at each time and space step based on the flow hydraulics acting on them, so no assumptions are made about incipient motion using Shield's criterion. This research examines how the interplay between hillslope GSD, hillslope attributes (gradient and length) and runoff

  5. Grain size indicators of sedimentary coupling between hillslopes and channels in a dryland basin

    Science.gov (United States)

    Hollings, Rory; Michealides, Katerina; Bliss Singer, Michael

    2017-04-01

    In dryland landscapes, heterogeneous and short-lived rainstorms generate runoff on slopes and streamflow in channels, which drive sediment movement from hillslope surfaces to channels and the transport of bed material sediment within channels. Long-term topographic evolution of drainage basins is partly determined by the relative balance of hillslope sediment supply to channels and the evacuation of channel sediment. However, it is not clear whether supply or evacuation is dominant over longer timescales (>>100 y) within dryland basins. One important indicator of local cumulative sediment transport is grain size (GS). On dryland hillslopes, grain size is governed over long timescales by weathering, but on short time scales (events to decades), is controlled by event-driven transport of the debris mantle. In the channel, GS reflects the input of hillslope sediment and the selective transport of particles along the bed. It is currently unknown how these two processes are expressed systematically within GS distributions on slopes and in channels within drylands, but this information could be useful to explain the history of the relative balance between hillslope sediment supply to channels and net sediment transport in the channel. We investigate this problem by combining field measurements of surface sediment grain size distributions in channels and on hillslopes with 1m LiDAR topography, >60 years of rainfall and channel discharge data from the Walnut Gulch Experimental Watershed (WGEW) in Arizona, and simple calculations of grain-sized based local stress distributions for various rainfall and discharge events. Hydrological scenarios of overland flow on hillslopes and channel flow conditions were derived from distributions of historic data at WGEW and were selected to reflect the wide range of storm intensities and durations, and channel discharges. 1) We used three quartiles of the entire distribution of measured discharge values for 80 locations throughout the

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

    Directory of Open Access Journals (Sweden)

    Vicente Braz Trindade

    2005-12-01

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

  7. Correlation of Grain Size, Stacking Fault Energy, and Texture in Cu-Al Alloys Deformed under Simulated Rolling Conditions

    Directory of Open Access Journals (Sweden)

    Ehab A. El-Danaf

    2015-01-01

    Full Text Available The effect of grain size and stacking fault energy (SFE on the strain hardening rate behavior under plane strain compression (PSC is investigated for pure Cu and binary Cu-Al alloys containing 1, 2, 4.7, and 7 wt. % Al. The alloys studied have a wide range of SFE from a low SFE of 4.5 mJm−2 for Cu-7Al to a medium SFE of 78 mJm−2 for pure Cu. A series of PSC tests have been conducted on these alloys for three average grain sizes of ~15, 70, and 250 μm. Strain hardening rate curves were obtained and a criterion relating twinning stress to grain size is established. It is concluded that the stress required for twinning initiation decreases with increasing grain size. Low values of SFE have an indirect influence on twinning stress by increasing the strain hardening rate which is reflected in building up the critical dislocation density needed to initiate mechanical twinning. A study on the effect of grain size on the intensity of the brass texture component for the low SFE alloys has revealed the reduction of the orientation density of that component with increasing grain size.

  8. 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

  9. 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

  10. The grain size distribution of settled sediment within storage reservoir Otmuchów

    Directory of Open Access Journals (Sweden)

    Głowski Robert

    2017-03-01

    Full Text Available The grain size distribution of settled sediment within storage reservoir Otmuchów. The river Nysa Kłodzka is flowing through the flat-reduction Otmuchów. There are localized two storage reservoirs Otmuchów and Nysa. The first of these reservoirs have been constructed in the period 1928-1933 and the filling was completed in 1934. Reservoir Nysa was completed in 1971. Both reservoirs are located within walking distance of each other, creating since 1971 cascade. Reservoir Otmuchów is located above the Nysa reservoir what cause, that in the bowl of the Otmuchów reservoir, the significant part of transported by Nysa Kłodzka sediments is deposited. When established after the 1997 flood damming levels, summer and winter, the length of the reservoir Otmuchów is suitably from 4.5 to 5 km. At the maximum impoundment level and a maximal capacity of 130.45 million m3 the reservoir length reach approx. 7 km. From the analysis of the satellite image can be seen advancing silting of the reservoir Otmuchów especially in the estuary zone of the Nysa Kłodzka. Obtained archival data about changes of the sediment grain size distribution in the longitudinal reservoir profile cover only the region of the still capacity extending a distance of 3 km from the cross-section of the dam. In this zone the fine particles of the suspended load with characteristic diameters ranging from 0.030 to 0.088 mm were embedded. In 2010, the authors presented the results of preliminary analysis of the silting process of the reservoir Otmuchów. The authors pointed out that there is a lack of the data about the dimension of the particles embedded in the usable capacity and flood capacity reserve (above 3 km from the dam causing visible on satellite photo silting. This paper presents the results of the sediment grain size distribution in the usable capacity of the reservoir and in the estuary region of the Nysa Kłodzka located in flood capacity reserve, obtained from the

  11. 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

  12. Expading fluvial remote sensing to the riverscape: Mapping depth and grain size on the Merced River, California

    Science.gov (United States)

    Richardson, Ryan T.

    This study builds upon recent research in the field of fluvial remote sensing by applying techniques for mapping physical attributes of rivers. Depth, velocity, and grain size are primary controls on the types of habitat present in fluvial ecosystems. This thesis focuses on expanding fluvial remote sensing to larger spatial extents and sub-meter resolutions, which will increase our ability to capture the spatial heterogeneity of habitat at a resolution relevant to individual salmonids and an extent relevant to species. This thesis consists of two chapters, one focusing on expanding the spatial extent over which depth can be mapped using Optimal Band Ratio Analysis (OBRA) and the other developing general relations for mapping grain size from three-dimensional topographic point clouds. The two chapters are independent but connected by the overarching goal of providing scientists and managers more useful tools for quantifying the amount and quality of salmonid habitat via remote sensing. The OBRA chapter highlights the true power of remote sensing to map depths from hyperspectral images as a central component of watershed scale analysis, while also acknowledging the great challenges involved with increasing spatial extent. The grain size mapping chapter establishes the first general relations for mapping grain size from roughness using point clouds. These relations will significantly reduce the time needed in the field by eliminating the need for independent measurements of grain size for calibrating the roughness-grain size relationship and thus making grain size mapping with SFM more cost effective for river restoration and monitoring. More data from future studies are needed to refine these relations and establish their validity and generality. In conclusion, this study adds to the rapidly growing field of fluvial remote sensing and could facilitate river research and restoration.

  13. Grain Size Analysis And Depositional Environment For Beach Sediments Along Abu Dhabi Coast United Arab Emirates

    Directory of Open Access Journals (Sweden)

    Saeed Al Rashedi

    2015-08-01

    Full Text Available The paper analysed the grain-size spectrum and textural parameters namely mean sorting skewness and kurtosis of Abu Dhabi coast in United Arab Emirates applying the ASTM sieves. For this purpose fifty seven samples were analysed. The results of the sieving analysis divulged that samples of the study area range between -2.63 pebble size to 2-39 Fine sands. The statistical analysis reveals that the sand is characteristically fine grained moderately well sorted to extremely poorly sorted. The sand distribution is strongly coarse and leptokurtic in nature. Abundance of the medium sand to fine sand shows the prevalence of comparatively moderate- to low-energy condition in the study area. Linear discriminate function of the samples indicates an Aeolian shallow marine deposition environment and less influence of fluvial 7 process.

  14. Electric field and grain size dependence of Meyer–Neldel energy in C60 films

    Science.gov (United States)

    Ullah, Mujeeb; Pivrikas, A.; Fishchuk, I.I.; Kadashchuk, A.; Stadler, P.; Simbrunner, C.; Sariciftci, N.S.; Sitter, H.

    2011-01-01

    Meyer–Neldel rule for charge carrier mobility measured in C60-based organic field-effect transistors (OFETs) at different applied source drain voltages and at different morphologies of semiconducting fullerene films was systematically studied. A decrease in the Meyer–Neldel energy EMN from 36 meV to 32 meV was observed with changing electric field in the channel. Concomitantly a decrease from 34 meV to 21 meV was observed too by increasing the grain size and the crystallinity of the active C60 layer in the device. These empiric findings are in agreement with the hopping-transport model for the temperature dependent charge carrier mobility in organic semiconductors with a Gaussian density of states (DOS). Experimental results along with theoretical descriptions are presented. PMID:21966084

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

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  16. Grains size and shape dependence of luminescence efficiency of Lu2O3:Eu thin screens

    Directory of Open Access Journals (Sweden)

    I.E. Seferis

    Full Text Available The aim of this work is to provide a comparative evaluation of luminescence efficiency of Lu2O3:Eu phosphors screens, in transmission mode, prepared with different grain shape and size, and manufactured by the sedimentation method. More specific, three screens were prepared with spherical grains of size 50 nm, 200 nm and 5 μm. Furthermore, two screens with rod-like shape grains and size of 500 nm and 1–8 μm. The behavior of Absolute Luminescence Efficiency (AE at low energy X-rays (50 kVp appeared to differ with the grains size and shape. Furthermore the rod-like grain screens appeared with reduced luminescence efficiency values.

  17. 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.

  18. Grain size effect on lattice of ni nanocrystals prepared through polyol method.

    Science.gov (United States)

    Okram, G S; Devi, Kh Namrata; Sanatombi, H; Soni, Ajay; Ganesan, V; Phase, D M

    2008-08-01

    Nanocrystalline nickel powders were prepared with grain size 'd' in the range 40-100 nm diameters through polyol method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used for characterization. XRD of the prepared samples consistently matched with standard fcc structure of nickel without any impurity peak. Detailed analysis and calculations using Scherrer equation for (111) peak revealed systematic increase in line width and peak shifting towards lower diffraction 2theta angles with decrease in nickel to ethylene glycol mole ratio. Different values of d estimated from various peaks of each sample suggested associated microstrains in the nanograins. Values of d estimated from X-ray diffraction patterns were compared with those obtained from atomic force microscopy and scanning electron microscopy results, and discussed. Observed lattice expansion is explained, on the basis of a theoretical model of linear elasticity.

  19. 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

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

    DEFF Research Database (Denmark)

    Frigaard, Peter; Wahl, Niels Arne

    2007-01-01

    The coastal landscape in Denmark is characterized by multiple areas of geologic, biologic and recreational interests both national and international. In the later years several guidelines have been set up for the coastal protection area. The aims for the future are to ensure the presence...... of naturally shaped beaches while at the same time the risk for erosion is reduced. For this reason beach nourishment is used widely along the Danish North Sea coast (called West Coast) and this method is preferred in preference to put up solid constructions. Beach nourishment is the primary method used...... by the Danish Coastal Authority. However problems have occurred in describing the spatial distribution of medium grain size d50 and the gradation U of the sediment used for beach nourishment. At the same time the sedimentary composition determines how fast the nourished beach is eroded and how the beach...

  1. Regional Association Analysis of MetaQTLs Delineates Candidate Grain Size Genes in Rice

    Directory of Open Access Journals (Sweden)

    Anurag V. Daware

    2017-05-01

    Full Text Available Molecular mapping studies which aim to identify genetic basis of diverse agronomic traits are vital for marker-assisted crop improvement. Numerous Quantitative Trait Loci (QTLs mapped in rice span long genomic intervals with hundreds to thousands of genes, which limits their utilization for marker-assisted genetic enhancement of rice. Although potent, fine mapping of QTLs is challenging task as it requires screening of large number of segregants to identify suitable recombination events. Association mapping offers much higher resolution as compared to QTL mapping, but detects considerable number of spurious QTLs. Therefore, combined use of QTL and association mapping strategies can provide advantages associated with both these methods. In the current study, we utilized meta-analysis approach to identify metaQTLs associated with grain size/weight in diverse Indian indica and aromatic rice accessions. Subsequently, attempt has been made to narrow-down identified grain size/weight metaQTLs through individual SNP- as well as haplotype-based regional association analysis. The study identified six different metaQTL regions, three of which were successfully revalidated, and substantially scaled-down along with GS3 QTL interval (positive control by regional association analysis. Consequently, two potential candidate genes within two reduced metaQTLs were identified based on their differential expression profiles in different tissues/stages of rice accessions during seed development. The developed strategy has broader practical utility for rapid delineation of candidate genes and natural alleles underlying QTLs associated with complex agronomic traits in rice as well as major crop plants enriched with useful genetic and genomic information.

  2. Finite element modeling of grain size effects on the ultrasonic microstructural noise backscattering in polycrystalline materials.

    Science.gov (United States)

    Bai, X; Tie, B; Schmitt, J-H; Aubry, D

    2018-07-01

    The correlation between ultrasonic wave propagation and polycrystalline microstructures has significant implications in nondestructive evaluation. An original numerical approach using the finite element method to quantify in both time and frequency domains the ultrasonic noise scattering due to the elastic heterogeneity of polycrystalline microstructures is presented. Based on the reciprocity theorem, it allows the scattering evaluation using mechanical data recorded only on the boundary of polycrystal instead of within its volume and is applicable to any polycrystalline aggregate regardless of its crystallographic or morphological characteristics. Consequently it gives a more realistic and accurate access of polycrystalline microstructures than the classical analytical models developed under the assumption of single scattering and the Born approximation. The numerical approach is proposed within the same unified theoretical framework as the classical analytical models, so it is possible to validate it in the cases of idealized microstructures for which the considered analytical models remain relevant. As an original result, assuming single phase, untextured and equiaxed microstructures, two-dimensional (2D) theoretical formulas are developed and a frequency-dependent coefficient is found compared to the classical three-dimensional (3D) formulas. 2D numerical simulations are then performed for idealized microstructures composed of hexagonal grains with a uniform grain-size. Three grain sizes are considered herein and involve different scattering regions. Good comparisons are obtained between theoretical and numerical estimates of the backscattering coefficient, which validate the numerical approach. Effects of the grain boundary orientations are analyzed by modeling an irregular hexagonal grain morphology and a random grain morphology generated by an established Voronoi approach. The origin of the significant oscillation level of backscattering is then investigated

  3. 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

  4. Atmospheric circulation patterns in Central and Eastern Europe during the Weichselian Pleniglacial inferred from loess grain-size records

    NARCIS (Netherlands)

    Bokhorst, M.P.; Vandenberghe, J.; Sümegi, P.; Lanczont, M.; Gerasimenko, N.P.; Matviishina, Z.N.; Markovic, S.B.; Frechen, M.

    2011-01-01

    This is a contribution to the reconstruction of the eolian transport processes and wind directions in south-eastern Europe during the Weichselian Pleniglacial. The study is based on eight loess sections: three west and five east of the Carpathian Mountains. The loess dispersal patterns in the area

  5. Predictability of seabed texture: spatial scaling of grain size and bathymetry on glaciated and non-glaciated shelves

    Science.gov (United States)

    Kostylev, V.

    2010-12-01

    In mapping seabed texture inherent predictability of sediment grain size is the key to the success of spatial interpolations. With low and stationary spatial variance the variable should be easy to predict while otherwise the results of interpolation are untrustworthy. Conceptual model known as 1/f^β noise offers a compelling way to describe predictability of environmental patterns. I have studied spatial spectra of mean grain size of surficial seabed sediments from two datasets roughly corresponding to glaciated (Canadian) and non-glaciated (US) shelves. Data for the Atlantic Canadian waters were obtained from Natural Resources Canada Expedition Database (23666 samples). For United States waters the Gulf of Mexico and Caribbean coastal and offshore data (17765 samples) as well as Atlantic Coast offshore surficial sediment data (33907 samples) were obtained from the usSEABED database. Spatial variances of mean grain size were calculated for samples separated by distance bins ranging from 1 to 1000 km. On scales from kilometers to hundreds of kilometers power spectrum of mean grain size in the studied datasets may be characterized as white noise (β = 0), indistinguishable from uniform random distribution (β =0.097 for Canada and β =0.009 for US). Power spectrum of grain size co-varies with bathymetry in US dataset across all scales. In the Canadian dataset this relationship holds up to 100 km, after which bathymetric and grain size variability become dissociated, and bathymetric variability increasing while sediment variability being relatively constant. Variance of US grain size data exhibits rapid increase in spatial variance on scales of 100 km and higher (β = 1.501). This exponent value falls between pink (β = 1) and red (Brownian, β = 2) noise and indicates that spatial patterns at larger sample separations are more predictable. There are several possible explanations for high spatial variance in grain size at relatively small sample separation (1 - 100

  6. 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.

  7. 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 been...... successfully prepared using a sintering time of less than 30min and without the need for a nitrogen atmosphere. A similarity between the grain size and powder particle size is found, which suggests a potential application of the SPS technique to prepare samples with a variety of grain sizes by tailoring...... the initial powder particle size. The SPS samples show higher strength than Al samples with an identical grain size prepared using thermo-mechanical processing, and a better strength-ductility combination, with the 1.3μm grain size sample showing a yield strength (σ0.2%) of 140MPa and a uniform elongation...

  8. 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.

  9. Grain boundary character distributions of coincidence site lattice boundaries in WC-Co composites with different WC grain sizes

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Xiaokun, E-mail: yuanxiaokun@bjut.edu.cn

    2013-12-05

    Highlights: •GBCDs of two kinds of CSL boundaries in cemented carbides are examined. •Carbide mean grain size is determinant in controlling the populations of CSL boundaries. •Rapid decrease of sigma2 boundaries occurs at higher speed than the coarsening of carbide grains. -- Abstract: The grain boundary character distributions of sigma2 and sigma13 boundaries were investigated in cemented carbide samples with different carbide grain sizes. Samples were prepared with average carbide grain sizes of about 0.5 μm, 1 μm and 2 μm, respectively. The electron backscattered diffraction measurements show that with the increase of the carbide grain size, populations of both sigma2 and sigma13 boundaries decrease; in the meantime, the sigma2 twist and sigma13 twist boundaries keep as the most common boundary types. The results suggest that the carbide grain size could be determinant in controlling the populations of coincidence site lattice boundaries in WC-Co composites.

  10. 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.

  11. Microstructure and mechanical strength of near- and sub-micrometre grain size copper prepared by spark plasma sintering

    DEFF Research Database (Denmark)

    Zhu, K. N.; Godfrey, A.; Hansen, Niels

    2017-01-01

    Spark plasma sintering (SPS) has been used to prepare fully dense samples of copper in a fully recrystallized condition with grain sizes in the near- and sub-micrometre regime. Two synthesis routes have been investigated to achieve grain size control: (i) SPS at different temperatures from 800 to...... been probed using hardness measurements and tensile testing, revealing an enhanced strength for samples with grain sizes less than ≈ 1 μm....... transmission electron microscope, and on electron back-scatter diffraction studies, confirms the samples are in a nearly fully recrystallized condition, with grains that are dislocation-free, and have a random texture, with a high fraction of high angle boundaries. The mechanical strength of the samples has...

  12. 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.

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

    KAUST Repository

    Rosas Aguilar, Jorge

    2013-05-01

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

  14. Grain size effect on the structural parameters of the stress induced epsilonhcp: martensite in iron-based shape memory alloy

    Directory of Open Access Journals (Sweden)

    Fabiana Cristina Nascimento

    2008-03-01

    Full Text Available The aim of this work was to study the effect of austenitic grain size (GS reduction on the structural parameters of the epsilonhcp - martensite in stainless shape memory alloy (SMA. Rietveld refinement data showed an expansion in c-axis and a reduction in a and b-axis with thermo-mechanical cycles for all samples analyzed. Samples with 75 < GS (µm < 129 were analyzed. It was also observed an increase of the unit cell volume in this phase with GS reduction. The smallest grain size sample (GS = 75 µm presented a c/a ratio of 1.649, and approximately 90% of total shape memory recovery.

  15. INFLUENCE OF AUSTENITE GRAIN SIZE TO DEVELOPMENT OF DECARBONIZATION IN PRODUCTION OF ROLLED STEEL

    Directory of Open Access Journals (Sweden)

    PARUSOV E. V.

    2016-08-01

    ]. The paper [11] acknowledges the influence of micro-additives of boron on changes in the austenite grain size and accordingly the length of borders in high-carbon steels with austenitizing temperature increase within the range of 900…1 100ºС. The purpose of work is to research the effect of austenite grain size on the decarburization depth in carbon (base steel and boron micro-alloyed steel.

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

    Science.gov (United States)

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

    2013-04-01

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

  17. Flow regulation in the Swiss Alps: a river network modelling approach to investigate the impacts on bed load and grain size distribution

    Science.gov (United States)

    Costa, A.; Molnar, P.; Schmitt, R. J. P.

    2017-12-01

    The grain size distribution (GSD) of river bed sediment results from the long term balance between transport capacity and sediment supply. Changes in climate and human activities may alter the spatial distribution of transport capacity and sediment supply along channels and hence impact local bedload transport and GSD. The effects of changed flow are not easily inferable due the non-linear, threshold-based nature of the relation between discharge and sediment mobilization, and the network-scale control on local sediment supply. We present a network-scale model for fractional sediment transport to quantify the impact of hydropower (HP) operations on river network GSD. We represent the river network as a series of connected links for which we extract the geometric characteristics from satellite images and a digital elevation model. We assign surface roughness based on the channel bed GSD. Bed shear stress is estimated at link-scale under the assumptions of rectangular prismatic cross sections and normal flow. The mass balance between sediment supply and transport capacity, computed with the Wilcock and Crowe model, determines transport rates of multiple grain size classes and the resulting GSD. We apply the model to the upper Rhone basin, a large Alpine basin in Switzerland. Since 1960s, changed flow conditions due to HP operations and sediment storage behind dams have potentially altered the sediment transport of the basin. However, little is known on the magnitude and spatial distribution of these changes. We force the model with time series of daily discharge derived with a spatially distributed hydrological model for pre and post HP scenarios. We initialize GSD under the assumption that coarse grains (d90) are mobilized only during mean annual maximum flows, and on the basis of ratios between d90 and characteristic diameters estimated from field measurements. Results show that effects of flow regulation vary significantly in space and in time and are grain size

  18. 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 (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.

  19. 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.

  20. Cross-linguistic transfer in bilinguals reading in two alphabetic orthographies: The grain size accommodation hypothesis.

    Science.gov (United States)

    Lallier, Marie; Carreiras, Manuel

    2018-02-01

    Reading acquisition is one of the most complex and demanding learning processes faced by children in their first years of schooling. If reading acquisition is challenging in one language, how is it when reading is acquired simultaneously in two languages? What is the impact of bilingualism on the development of literacy? We review behavioral and neuroimaging evidence from alphabetic writing systems suggesting that early bilingualism modulates reading development. Particularly, we show that cross-linguistic variations and cross-linguistic transfer affect bilingual reading strategies as well as their cognitive underpinnings. We stress the fact that the impact of bilingualism on literacy acquisition depends on the specific combination of languages learned and does not manifest itself similarly across bilingual populations. We argue that these differences can be explained by variations due to orthographic depth in the grain sizes used to perform reading and reading-related tasks. Overall, we propose novel hypotheses to shed light on the behavioral and neural variability observed in reading skills among bilinguals.

  1. 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.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1996-07-01

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

  3. 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.

  4. 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.

  5. 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.

  6. Historical atmospheric pollution trends in Southeast Asia inferred from lake sediment records.

    Science.gov (United States)

    Engels, S; Fong, L S R Z; Chen, Q; Leng, M J; McGowan, S; Idris, M; Rose, N L; Ruslan, M S; Taylor, D; Yang, H

    2018-04-01

    Fossil fuel combustion leads to increased levels of air pollution, which negatively affects human health as well as the environment. Documented data for Southeast Asia (SEA) show a strong increase in fossil fuel consumption since 1980, but information on coal and oil combustion before 1980 is not widely available. Spheroidal carbonaceous particles (SCPs) and heavy metals, such as mercury (Hg), are emitted as by-products of fossil fuel combustion and may accumulate in sediments following atmospheric fallout. Here we use sediment SCP and Hg records from several freshwater lentic ecosystems in SEA (Malaysia, Philippines, Singapore) to reconstruct long-term, region-wide variations in levels of these two key atmospheric pollution indicators. The age-depth models of Philippine sediment cores do not reach back far enough to date first SCP presence, but single SCP occurrences are first observed between 1925 and 1950 for a Malaysian site. Increasing SCP flux is observed at our sites from 1960 onward, although individual sites show minor differences in trends. SCP fluxes show a general decline after 2000 at each of our study sites. While the records show broadly similar temporal trends across SEA, absolute SCP fluxes differ between sites, with a record from Malaysia showing SCP fluxes that are two orders of magnitude lower than records from the Philippines. Similar trends in records from China and Japan represent the emergence of atmospheric pollution as a broadly-based inter-region environmental problem during the 20th century. Hg fluxes were relatively stable from the second half of the 20th century onward. As catchment soils are also contaminated with atmospheric Hg, future soil erosion can be expected to lead to enhanced Hg flux into surface waters. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. 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.

  8. Mean grain size detection of DP590 steel plate using a corrected method with electromagnetic acoustic resonance.

    Science.gov (United States)

    Wang, Bin; Wang, Xiaokai; Hua, Lin; Li, Juanjuan; Xiang, Qing

    2017-04-01

    Electromagnetic acoustic resonance (EMAR) is a considerable method to determine the mean grain size of the metal material with a high precision. The basic ultrasonic attenuation theory used for the mean grain size detection of EMAR is come from the single phase theory. In this paper, the EMAR testing was carried out based on the ultrasonic attenuation theory. The detection results show that the double peaks phenomenon occurs in the EMAR testing of DP590 steel plate. The dual phase structure of DP590 steel is the inducement of the double peaks phenomenon in the EMAR testing. In reaction to the phenomenon, a corrected method with EMAR was put forward to detect the mean grain size of dual phase steel. Compared with the traditional attenuation evaluation method and the uncorrected method with EMAR, the corrected method with EMAR shows great effectiveness and superiority for the mean grain size detection of DP590 steel plate. Copyright © 2016. Published by Elsevier B.V.

  9. Analysis of grain size effects on transformation-induced plasticity based on a discrete dislocation-transformation model

    NARCIS (Netherlands)

    Shi, J.; Turteltaub, S.; Van der Giessen, E.

    2010-01-01

    There is much interest recently in the possibility of combining two strengthening effects, namely the reduction of grain size (Hall-Fetch effect) and the transformation-induced plasticity effect (strengthening due to a martensitic transformation). The present work is concerned with the analysis of

  10. 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.

  11. 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

  12. 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 ...

  13. 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.

  14. 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.

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

    DEFF Research Database (Denmark)

    Stevens, Thomas; Lu, HY

    2009-01-01

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

  16. Impacts of grain size sorting and chemical weathering on the geochemistry of Jingyuan loess in the northwestern Chinese Loess Plateau

    NARCIS (Netherlands)

    Liang, L.; Sun, Y.; Beets, C.J.; Prins, M.A.; Wu, F.; Vandenberghe, J.

    2013-01-01

    Major and trace elemental compositions of loess samples collected from the Jingyuan section in the northwestern Chinese Loess Plateau (CLP) were analyzed to investigate the potential impacts of grain size sorting and chemical weathering on the loess geochemistry and to extract appropriate

  17. 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.

  18. 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 ...

  19. 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

  20. 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 The Vickers hardness of several well-characterized grades of WC-Co (23 in total) was measured. The mean grain size of these samples ranged from 0.6 to 5.0 mums and the cobalt content from 6 to 50 wt%. An empirical formula between hardness of WC...

  1. 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.

  2. The mean grain size determination of boron carbide (B4C)-aluminium (Al) and boron carbide (B4C)-nickel (Ni) composites by ultrasonic velocity technique

    International Nuclear Information System (INIS)

    Unal, Ridvan; Sarpuen, Ismail H.; Yalim, H. Ali; Erol, Ayhan; Ozdemir, Tuba; Tuncel, Sabri

    2006-01-01

    In this study, the mean grain size of ceramic-metal composites, made from boron carbide (B 4 C)-aluminium (Al)-nickel (Ni) powders, has been determined with ultrasonic velocity technique by using a 2 MHz transducer. An ultrasonic velocity-grain size master graph was plotted using a 4 MHz ultrasonic transducer. The results were compared to the mean grain size obtained from SEM (Scanning Electron Microscopy) images

  3. Grain-size-induced weakening of H2O ices I and II and associated anisotropic recrystallization

    Science.gov (United States)

    Stern, L.A.; Durham, W.B.; Kirby, S.H.

    1997-01-01

    Grain-size-dependent flow mechanisms tend to be favored over dislocation creep at low differential stresses and can potentially influence the rheology of low-stress, low-strain rate environments such as those of planetary interiors. We experimentally investigated the effect of reduced grain size on the solid-state flow of water ice I, a principal component of the asthenospheres of many icy moons of the outer solar system, using techniques new to studies of this deformation regime. We fabricated fully dense ice samples of approximate grain size 2 ?? 1 ??m by transforming "standard" ice I samples of 250 ?? 50 ??m grain size to the higher-pressure phase ice II, deforming them in the ice II field, and then rapidly releasing the pressure deep into the ice I stability field. At T ??? 200 K, slow growth and rapid nucleation of ice I combine to produce a fine grain size. Constant-strain rate deformation tests conducted on these samples show that deformation rates are less stress sensitive than for standard ice and that the fine-grained material is markedly weaker than standard ice, particularly during the transient approach to steady state deformation. Scanning electron microscope examination of the deformed fine-grained ice samples revealed an unusual microstructure dominated by platelike grains that grew normal to the compression direction, with c axes preferentially oriented parallel to compression. In samples tested at T ??? 220 K the elongation of the grains is so pronounced that the samples appear finely banded, with aspect ratios of grains approaching 50:1. The anisotropic growth of these crystallographically oriented neoblasts likely contributes to progressive work hardening observed during the transient stage of deformation. We have also documented remarkably similar microstructural development and weak mechanical behavior in fine-grained ice samples partially transformed and deformed in the ice II field.

  4. Modeling grain size adjustments in the downstream reach following run-of-river development

    Science.gov (United States)

    Fuller, Theodore K.; Venditti, Jeremy G.; Nelson, Peter A.; Palen, Wendy J.

    2016-04-01

    Disruptions to sediment supply continuity caused by run-of-river (RoR) hydropower development have the potential to cause downstream changes in surface sediment grain size which can influence the productivity of salmon habitat. The most common approach to understanding the impacts of RoR hydropower is to study channel changes in the years following project development, but by then, any impacts are manifest and difficult to reverse. Here we use a more proactive approach, focused on predicting impacts in the project planning stage. We use a one-dimensional morphodynamic model to test the hypothesis that the greatest risk of geomorphic change and impact to salmon habitat from a temporary sediment supply disruption exists where predevelopment sediment supply is high and project design creates substantial sediment storage volume. We focus on the potential impacts in the reach downstream of a powerhouse for a range of development scenarios that are typical of projects developed in the Pacific Northwest and British Columbia. Results indicate that increases in the median bed surface size (D50) are minor if development occurs on low sediment supply streams (<1 mm for supply rates 1 × 10-5 m2 s-1 or lower), and substantial for development on high sediment supply streams (8-30 mm for supply rates between 5.5 × 10-4 and 1 × 10-3 m2 s-1). However, high sediment supply streams recover rapidly to the predevelopment surface D50 (˜1 year) if sediment supply can be reestablished.

  5. Grain-size dependence of the magnetic properties of street dusts from Warsaw, Poland

    Science.gov (United States)

    Dytłow, Sylwia; Winkler, Aldo; Sagnotti, Leonardo

    2015-04-01

    In recent years, in connection with a substantial development of transportation in urban areas, vehicular traffic increased its importance as source of pollution and consequent cause of health problems in urban environments. In fact, it is well established that the concentration and size of pollution related particulate matter (PM) are important factors affecting human health. The aim of this study is to identify the variations of the magnetic properties and of the chemical composition of different granulometric fractions from street dusts collected at four locations in Warsaw: the city center, a suburb, a tramline and a big crossroad. Dust samples were mechanically sieved and classified using the laboratory shaker with a standard sieve set (0.5 mm, 0.25 mm, 0.1 mm and 0.071 mm). Data show a distribution of magnetic susceptibility (χ) in the wide range of 80-370 × 10-8 m3kg-1. Comparison of magnetic parameters shows that the street dust contains the pollution characteristics for air and soil. The samples were characterized by uniform magnetic mineralogy, typical for fine-grained magnetite, in a grain size range between pseudo-single-domain and fine multi-domain, with a small contribution from ultrafine superparamagnetic particles (~2-3.5 %). The street dust contains, as usual for the urban areas, spherical magnetic particles produced by fossil fuel combustion processes and mixture of irregular angular iron-oxides grains containing other elements. The magnetic susceptibility and hysteresis properties of the dusts have been analyzed in detail; the temperature variation of the saturation of remanent magnetization and of the magnetic susceptibility revealed that the main magnetic mineral, for all the fractions, is almost stoichiometric magnetite, with the finest fractions (d=0.1 mm, 0.071 mm and d

  6. 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.

  7. Mediterranean sea water budget long-term trend inferred from salinity observations

    Science.gov (United States)

    Skliris, N.; Zika, J. D.; Herold, L.; Josey, S. A.; Marsh, R.

    2018-01-01

    Changes in the Mediterranean water cycle since 1950 are investigated using salinity and reanalysis based air-sea freshwater flux datasets. Salinity observations indicate a strong basin-scale multi-decadal salinification, particularly in the intermediate and deep layers. Evaporation, precipitation and river runoff variations are all shown to contribute to a very strong increase in net evaporation of order 20-30%. While large temporal uncertainties and discrepancies are found between E-P multi-decadal trend patterns in the reanalysis datasets, a more robust and spatially coherent structure of multi-decadal change is obtained for the salinity field. Salinity change implies an increase in net evaporation of 8 to 12% over 1950-2010, which is considerably lower than that suggested by air-sea freshwater flux products, but still largely exceeding estimates of global water cycle amplification. A new method based on water mass transformation theory is used to link changes in net evaporation over the Mediterranean Sea with changes in the volumetric distribution of salinity. The water mass transformation distribution in salinity coordinates suggests that the Mediterranean basin salinification is driven by changes in the regional water cycle rather than changes in salt transports at the straits.

  8. Can grain size, sorting and grading patterns be used to identify supercritical bedforms in cores?

    Science.gov (United States)

    Acikalin, Sanem; Cartigny, Matthieu; Ventra, Dario; Bijkerk, Jochem; Neal, Adrian

    2017-04-01

    Reservoir characterisation is often based on integrated studies of few to several tools such as seismic profiles, wireline logs, borehole image, core observations and petrography. Typically these tools either provide information about the regional architecture of the reservoir or data source is restricted to a single point such as to core(s) or a well bore(s). This relatively large gap in scale of various data sources is likely to result in missing key information for reservoir characterisation, such as bedforms. Outcrop studies, where available, provide very valuable data; and upscaling/downscaling of the information obtained from outcrops are likely to fill the gap between the scales of core/well and seismic profile. Recent flume experiments and submarine observations have increased our knowledge about flow dynamics and sediment deposition processes. One of the outcomes of these studies is the 'cyclic steps' which are recognised as a new bedform category, developing at maximum Froude numbers. Typically, they form aggredational packages composed of mainly structureless sandstones with undulating geometries. In one aggredational bedset, various bed-scale fabrics are likely to occur in different parts of the deposits due to the lateral change in flow characteristics and associated sediment transport processes. Cyclic steps are typically in a sub-seismic scale, yet they are very difficult to recognise in core. Better understanding of stacking pattern of bed-scale properties is the key for the recognition of cyclic steps in cores, however, this may be difficult due to the restricted core size. In this study, we aimed to form a link from outcrop scale properties of cyclic steps to core and micro-scale features (typically grain size, sorting and grading) in order to be make an attempt to use petrography as a tool for recognition of the cyclic steps in core. For this case study, outcrops of Late Carboniferous sandstones of the Lower Kinderscout Grit, that were deposited

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

    NARCIS (Netherlands)

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

    2005-01-01

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

  10. Analysis of the grain size evolution for ferrite formation in Fe-C-Mn steels using a 3D model under a mixed-mode interface condition

    NARCIS (Netherlands)

    Fang, H.; Mecozzi, M.G.; Brück, E.H.; van der Zwaag, S.; van Dijk, N.H.

    2018-01-01

    A 3D model has been developed to predict the average ferrite grain size and grain size distribution for an austenite-to-ferrite phase transformation during continuous cooling of an Fe-C-Mn steel. Using a Voronoi construction to represent the austenite grains, the ferrite is assumed to nucleate at

  11. 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.

  12. Effect of Initial Grain Size on Ductile Damage of AA1100-O at High Strain Rate and Stress Triaxiality

    Science.gov (United States)

    Testa, Gabriel; Bonora, Nicola; Ruggiero, Andrew; Iannitti, Gianluca; Gentile, Domenico

    2017-06-01

    The effect of the initial grain size on ductile damage development in AA1100-O aluminum at high strain rate and severe stress triaxiality was investigated. Symmetric Taylor impact (rod-on-rod, RoR) specimens were machined from extruded bars and annealed at 350 ° C for different times to obtain three grain sizes (147, 159 e 189 μm). Numerical parametric investigation to assess the impact velocity for incipient damage development were made using a modified formulation of Rusinek-Klepaczko constitutive model and the Bonora damage model considering pressure effect and stochastic material variability on the damage parameters. Tests at estimated impact velocities, for incipient and fully developed damage condition, were performed. Soft recovered specimens were sectioned and polished to evaluate damage extension to compare with numerical simulation results.

  13. Grain Size and Interface Dependence of Bias Stress Stability of n-Type Organic Field Effect Transistors.

    Science.gov (United States)

    Ahmed, Rizwan; Simbrunner, Clemens; Baig, M A; Sitter, H

    2015-10-14

    The effect of grain size and interface dependence of bias stress stability of C60-based n-type organic field effect transistors (OFETs) has been studied. It has been realized that, with increasing grain size of C60, the bias stress induced threshold voltage shift can be controlled and this effect is mainly attributed to the mechanism of charge trapping at grain boundaries. It is further studied that the growth of C60 on the surface of parylene at elevated substrate temperature leads to the creation of radicals at the interface between the active layer and the gate dielectric. These radicals help to improve the bias stress stability of C60-based n-type OFETs. For achieving the bias stress stability, we have presented a procedure of creation of radicals at the interface between C60 and parylene in single gate OFETs instead of dual gate OFETs.

  14. Retrieval of snow grain size and soot pollution on sea ice with the optical satellite remote sensing instrument MODIS

    Energy Technology Data Exchange (ETDEWEB)

    Wiebe, Heidrun; Heygster, Georg [Institute for Environmental Physics, University of Bremen (Germany); Zege, Eleonora [Institute of Physics, National Academy of Sciences of Belarus, Minsk (Belarus)

    2009-07-01

    Snow fields have potentially significant effects on the planetary albedo and climate. Development of satellite remote sensing of snow is of a great importance particularly for monitoring of snow age, pollution, and grain sizes over the polar regions difficult to access. As it follows from numerous experimental studies of optical and microphysical snow properties, a snow layer is a multiple scattering close packed medium with irregular shaped non-uniform grains. The developed algorithm retrieves the effective snow grain size and pollution amount, which does not imply any specific snow model, do not use any a priori suggestions of snow grain shape, and uses the multi-spectral information provided by a satellite optical instrument MODIS. It is especially suitable for polar regions, as it provides a reliable retrieval even at low sun elevations.

  15. 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...... 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...

  16. Critical current density versus normal-state resistivity in granular high-temperature superconductors with different average grain size

    International Nuclear Information System (INIS)

    Curras, S.R.; Veira, J.A.; Maza, J.; Vidal, Felix

    2000-01-01

    The resistivity, ρ, and the critical current density at zero applied magnetic field, J c , of ceramic Y 1 Ba 2 Cu 3 O 7-δ samples with different average grain size, a (from 5 to 14 μm), are reported. These results show that at a given temperature J c depends only on the specific contact resistance of the average grain boundary junction, ρ□, so that the product J c ρ□ is sample independent. The relevance of ρ□ and not of a on J c has been further tested on a subset of samples having very different average grain size but similar ρ□ for which negligible variations of J c are observed. (author)

  17. Awns reduce grain number to increase grain size and harvestable yield in irrigated and rainfed spring wheat.

    Science.gov (United States)

    Rebetzke, G J; Bonnett, D G; Reynolds, M P

    2016-04-01

    Genotypic variation in ear morphology is linked to differences in photosynthetic potential to influence grain yield in winter cereals. Awns contribute to photosynthesis, particularly under water-limited conditions when canopy assimilation is restricted. We assessed performance of up to 45 backcross-derived, awned-awnletted NILs representing four diverse genetic backgrounds in 25 irrigated or rainfed, and droughted environments in Australia and Mexico. Mean environment grain yields were wide-ranging (1.38-7.93 t ha(-1)) with vegetative and maturity biomass, plant height, anthesis date, spike number, and harvest index all similar (P >0.05) for awned and awnletted NILs. Overall, grain yields of awned-awnletted sister-NILs were equivalent, irrespective of yield potential and genetic background. Awnletted wheats produced significantly more grains per unit area (+4%) and per spike (+5%) reflecting more fertile spikelets and grains in tertiary florets. Increases in grain number were compensated for by significant reductions in grain size (-5%) and increased frequency (+0.8%) of small, shrivelled grains ('screenings') to reduce seed-lot quality of awnletted NILs. Post-anthesis canopies of awnletted NILs were marginally warmer over all environments (+0.27 °C) but were not different and were sometimes cooler than awned NILs at cooler air temperatures. Awns develop early and represented up to 40% of total spikelet biomass prior to ear emergence. We hypothesize that the allocation of assimilate to large and rapidly developing awns decreases spikelet number and floret fertility to reduce grain number, particularly in distal florets. Individual grain size is increased to reduce screenings and to increase test weight and milling quality, particularly in droughted environments. Despite the average reduction in grain size, awnless lines could be identified that combined higher grain yield with larger grain size, increased grain protein concentration, and reduced screenings. © The

  18. Grain-size analysis and sediment dynamics of hurricane-induced event beds in a coastal New England pond

    Science.gov (United States)

    Castagno, K. A.; Ruehr, S. A.; Donnelly, J. P.; Woodruff, J. D.

    2017-12-01

    Coastal populations have grown increasingly susceptible to the impacts of tropical cyclone events as they grow in size, wealth, and infrastructure. Changes in tropical cyclone frequency and intensity, augmented by a changing climate, pose an increasing threat of property damage and loss of life. Reconstructions of intense-hurricane landfalls from a series of southeastern New England sediment cores identify a series of events spanning the past 2,000 years. Though the frequency of these landfalls is well constrained, the intensity of these storms, particularly those for which no historical record exists, is not. This study analyzes the grain-size distribution of major storm event beds along a transect of sediment cores from a kettle pond in Falmouth, MA. The grain-size distribution of each event is determined using an image processing, size, and shape analyzer. The depositional patterns and changes in grain-size distribution in these fine-grained systems may both spatially and temporally reveal characteristics of both storm intensity and the nature of sediment deposition. An inverse-modeling technique using this kind of grain-size analysis to determine past storm intensity has been explored in back-barrier lagoon systems in the Caribbean, but limited research has assessed its utility to assess deposits from back-barrier ponds in the northeastern United States. Increases in hurricane intensity may be closely tied to increases in sea surface temperature. As such, research into these prehistoric intervals of increased frequency and/or intensity provides important insight into the current and future hurricane risks facing coastal communities in New England.

  19. 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

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

    Science.gov (United States)

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

    2015-08-18

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

  1. 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.

  2. Evolution of grain sizes and orientations during phase transitions in hydrous Mg2SiO4

    Science.gov (United States)

    Rosa, Angelika D.; Hilairet, Nadège; Ghosh, Sujoy; Perrillat, Jean-Philippe; Garbarino, Gaston; Merkel, Sébastien

    2016-10-01

    Transformation microstructures in mantle minerals, such as (Mg,Fe)2SiO4, are critical for predicting the rheological properties of rocks and the interpretation of seismic observations. We present in situ multigrain X-ray diffraction experiments on hydrous Mg2SiO4 at the P/T conditions relevant for deep cold subducting slabs (up to 40 GPa and 850°C) at a low experimental strain rate ( 4 * 10-6s-1). We monitor the orientations of hundreds of grains and grain size variations during the series of α-β-γ (forsterite-wadsleyite-ringwoodite) phase transformations. Microtextural results indicate that the β and an intermediate γ* phase grow incoherently relatively to the host α phase consistent with a nucleation and growth model. The β and γ phases exhibit orientation relationships which are in agreement with previous ex situ observations. The β and intermediate γ* show texturing due to moderate differential stress in the sample. Both the α-β and α-γ transformation induce significant reductions of the mean sample grain size of up to 90% that starts prior to the appearance of the daughter phase. Apart from the γ*, in the newly formed β and γ phases, the nucleation rate is faster than the growth rate, inhibiting the formation of large grains. These results on grain orientations and grain size reductions in relation to transformation kinetics should allow refining existing slab strength models.

  3. 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.

  4. SAGE 2014: Grain size variability across the Sunlight Absorption on the Greenland ice sheet Experiment (SAGE) traverse route

    Science.gov (United States)

    Courville, Z.; Polashenski, C.; Domine, F.; Bergin, M. H.; Chen, J.; Farnsworth, L.; Stwertka, C.; Stewart, M. C.; Dibb, J. E.

    2014-12-01

    In 2014, researchers from the US Army Corps of Engineers Cold Region Research and Engineering Laboratory, Dartmouth College, the University of New Hampshire, Georgia Tech, University of Wisconsin, University of Michigan, and NASA-Langley completed the second year of a ground-based traverse of the Greenland Ice Sheet. Samples from 67 locations were extracted from shallow snow pits and analyzed for trace elements, black carbon (see Polashenski et al. and Dibb et al. in session C004: Aerosols and the Cryosphere), and snow grain size (in terms of specific surface area) at depths comprising at least the previous year's worth of snow accumulation at each site. In addition, surface characteristics of the snow including albedo, surface roughness and meteorological forcing were determined. Here, we present the spatial distribution of grain size reported as specific surface area determined from field measurements using the Takuvik International Laboratory DUal Frequency Integrating Sphere for Snow Specific area measurement (DUFISSS) instrument and from laboratory-based stereology and micro-CT measurements from snow samples that were preserved and shipped back to the lab. Grain sizes from 2014 are compared to 2013 results at coincident locations and comparable depths, and compared to the intervening year's worth of meteorological data from Automated Weather Stations (AWSs) assembled by the SAGE field team at four locations along the 2013 and 2014 routes.

  5. 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.

  6. 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

  7. Sputter deposition of Ce(Sm,Y)O2 thin films: linking phase instability to grain size

    Science.gov (United States)

    Van Steenberge, S.; Depla, D.

    2016-06-01

    (1  -  x)CeO2  -  xMO1.5 thin films (with M  =  Y or Sm) were deposited using DC reactive dual magnetron sputtering. The influence of the substitution of Ce4+ ions by M3+ ions in the ceria fluorite structure is investigated with x-ray diffraction and scanning electron microscopy to provide a description of the thin film microstructural and textural evolution at room temperature and at elevated temperatures. Phase analysis shows that the fluorite structure can be maintained until a composition of x  =  0.40 of Y or Sm. At higher values of x, a diphasic region is observed. The films are thermally stable because no restructuring occurs when they are heated. A decrease in grain size is observed before the diphasic region forms which is typically explained from a reduced adatom mobility. However, the microstructure throughout the composition range is indicative of zone T growth. These findings illustrate that while the growth of a thin film is a kinetically driven process, the observed decrease in grain size is no evidence of a reduced surface adatom mobility but of imposed thermodynamic barriers. The critical composition for the grain size change coincides not only for both material systems (M  =  Y or Sm), but also with reported values of crystallographic structural changes in bulk material.

  8. Comparisons of global ozone trends inferred from the BUV experiment on Nimbus 4 and the ground-based network

    Science.gov (United States)

    Heath, D. F.

    1981-01-01

    Preliminary comparisons between global ozone burdens derived from the backscattered ultraviolet (BUV) experiment on Nimbus 4 and those inferred from an analysis of ground-based network data seem to indicate significant differences in the inter-annual variability of ozone. Some of the observed differences may be due to improper weighting of the ground-based network data, slowly changing planetary wave structure over the fixed station, of small inter-annual changes in meridional transport parameters. There is also some evidence which indicates that the polar stratosphere at high latitudes may represent an important ozone storage resevoir which tends to compensate for large scale changes observed in the regions outside of the polar stratosphere. Possible consequences of this are that the global trends derived from ground based ozone measurements may not be valid and furthermore that the current satellite techniques by themselves may be sufficient. An ozone monitoring system which includes observations from satellites, ground-based stations, balloons and rockets may be necessary.

  9. THE INFLUENCE MECHANISM OF FERRITE GRAIN SIZE ON STRENGTH STRESS AT THE FATIGUE OF LOW-CARBON STEEL

    Directory of Open Access Journals (Sweden)

    I. A. Vakulenko

    2014-01-01

    Full Text Available Purpose. Explanation of the influence mechanism of ferrite grain size on the fatigue strength of low-carbon steel. Methodology. Material for research is the low-carbon steel with 0.1% of carbon contnent. The different size of ferrite grain was obtained due to varying the degree of cold plastic deformation and temperature of annealing. The estimation of grain size was conducted using methodologies of quantitative metallography. The microstructure of metal was investigated under a light microscope with increase up to 1500 times. As a fatigue response the fatigue strength of metal – a maximal value of load amplitude with endless endurance limit of specimen was used. Fatigue tests were carried out using the test machine «Saturn-10», at the symmetric cycle of alternating bend loading. Findings. On the basis of research the dependence for fatigue strength of low-carbon steel, which is based on an additive contribution from hardening of solid solution by the atoms of carbon, boundary of the ferrite grain and amount of mobile dislocations was obtained. It was established that as the grainy structure of low-carbon steel enlarges, the influence of grain size on the fatigue strength level is reduced. For the sizes of grains more than 100 mcm, basic influence on fatigue strength begins to pass to the solid solution hardening, which is determined by the state of solid solution of introduction. Originality. From the analysis of the obtained dependences it ensues that with the increase of ferrite grain size the required amount of mobile dislocations for maintenance of conditions for spreading plastic deformation becomes less dependent from the scheme of metal loading. Practical value. The obtained results present certain practical interest when developing of recommendations, directed on the increase of resource of products work from low-carbon steels in the conditions of cyclic loading. Estimation of separate contribution of the studied processes of

  10. [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 (soil water evaporation, deeper soil desiccation, and surface soil salt accumulation, while coarse-textured (0.063-2 mm) deposits inhibited soil water evaporation and decreased deeper soil water loss and surface soil salt accumulation. The inhibition effect of the 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.

  11. Effects of γ' Precipitation, Dislocation Density, and Grain Size on Stress-Relaxation Properties of INCONEL X-750 Helical Springs

    Science.gov (United States)

    Ha, Jeong Won; Seong, Baek Seok; Woo, Wanchuck; Jeong, Hi Won; Choi, Yoon Suk; Kang, Namhyun

    2017-08-01

    INCONEL X-750 specimens were manufactured into helical springs by drawing and coiling followed by aging. They were subsequently subjected to stress-relaxation tests. Stress relaxation is the important property of springs that are compressed at elevated temperatures. To understand stress relaxation, this study investigated the effect of the drawing ratio (DR) on the γ' size and volume fraction, grain size, carbide volume fraction, and dislocation density. Small-angle neutron scattering was used to measure the size and volume fraction of γ' phase, and X-ray diffraction was employed to analyze the dislocation density in the springs as a function of the DR. The smallest DR specimen (DR0) had a longer free length than the larger DR specimens (DR17 and DR42) after the stress-relaxation test was completed at 773 K (500 °C) for 300 hours. However, the size and volume fraction of γ', along with the dislocation density, had no influence on the stress relaxation of the INCONEL X-750 springs. The decreased grain size ( d) due to an increase in the DR was the main factor in the increase in the stress relaxation of the springs. The decrease in grain size displayed a nonlinear relationship with the increase in stress relaxation. The stress-relaxation behavior relationship was d -3. Grain boundaries were determined to play a role in dislocation sink via transmission electron microscopy (TEM) observations. Grain boundary diffusion accommodated by slip was responsible for the stress-relaxation properties of the spring at an elevated temperature (773 K = 500 °C).

  12. 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%.

  13. 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.

  14. 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.

  15. Effects of grain size from micro scale to nanoscales on the yield strain of brass under compressive and tensile stresses using a Kelvin probing technique

    International Nuclear Information System (INIS)

    Li, D.Y.; Wang, L.; Li, W.

    2004-01-01

    Effects of grain size on the yield strain of brass (70-30), respectively, under tensile and compressive stresses were investigated using a Kelvin probe, a highly sensitive instrument for measuring the electron work function (EWF) of materials. The average grain size under study varied from 20 nm to 80 μm. The nanocrystalline structure was generated by sandblasting followed by recovery treatment. Results of the EWF measurement demonstrated that the yield strain differed as applied stress changed from tensile to compressive. The magnitude of compressive yield strain is larger than that of tensile yield strain. It was observed that with a decrease in grain size, the difference in magnitude between the compressive yield strain and the tensile yield strain decreased. The mechanism responsible for the difference in yield strain and the effect of grain size on the yield strain are discussed

  16. 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.

    with a concentration of 0.8 % (Tab.1). Both these values show an identical trend in shell content, silt+clay content. 3 At Chinnankudy High Tide (HT) region, there is an increase of silt and clay content by 1.09 %. In the berm samples, a general... (Tab.2). In the present study region, graphic mean size of the LT, HT samples of Poompuhar show that sediments are of medium grained in pre and post-tsunami whereas the berm samples display a change in characteristics from medium grained...

  17. Impact of change in erosion rate and landscape steepness on hillslope and fluvial sediments grain size in the Feather River basin (Sierra Nevada, California)

    OpenAIRE

    M. Attal; S. M. Mudd; M. D. Hurst; B. Weinman; K. Yoo; M. Naylor

    2015-01-01

    The characteristics of the sediment transported by rivers (e.g. sediment flux, grain size distribution – GSD) dictate whether rivers aggrade or erode their substrate. They also condition the architecture and properties of sedimentary successions in basins. In this study, we investigate the relationship between landscape steepness and the grain size of hillslope and fluvial sediments. The study area is located within the Feather River basin in northern California, and studied...

  18. Magmatic Focusing to Mid-Ocean Ridges: The Role of Grain-Size Variability and Non-Newtonian Viscosity

    Science.gov (United States)

    Turner, Andrew J.; Katz, Richard F.; Behn, Mark D.; Keller, Tobias

    2017-12-01

    Melting beneath mid-ocean ridges occurs over a region that is much broader than the zone of magmatic emplacement that forms the oceanic crust. Magma is focused into this zone by lateral transport. This focusing has typically been explained by dynamic pressure gradients associated with corner flow, or by a sublithospheric channel sloping upward toward the ridge axis. Here we discuss a novel mechanism for magmatic focusing: lateral transport driven by gradients in compaction pressure within the asthenosphere. These gradients arise from the covariation of melting rate and compaction viscosity. The compaction viscosity, in previous models, was given as a function of melt fraction and temperature. In contrast, we show that the viscosity variations relevant to melt focusing arise from grain-size variability and non-Newtonian creep. The asthenospheric distribution of melt fraction predicted by our models provides an improved explanation of the electrical resistivity structure beneath one location on the East Pacific Rise. More generally, we find that although grain-size and non-Newtonian viscosity are properties of the solid phase, their effect on melt transport beneath mid-ocean ridges is more profound than their effect on the mantle corner flow.

  19. 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.

  20. 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

  1. Standard practice for determining average grain size using electron backscatter diffraction (EBSD) in fully recrystallized polycrystalline materials

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2010-01-01

    1.1 This practice is used to determine grain size from measurements of grain areas from automated electron backscatter diffraction (EBSD) scans of polycrystalline materials. 1.2 The intent of this practice is to standardize operation of an automated EBSD instrument to measure ASTM G directly from crystal orientation. The guidelines and caveats of E112 apply here, but the focus of this standard is on EBSD practice. 1.3 This practice is only applicable to fully recrystallized materials. 1.4 This practice is applicable to any crystalline material which produces EBSD patterns of sufficient quality that a high percentage of the patterns can be reliably indexed using automated indexing software. 1.5 The practice is applicable to any type of grain structure or grain size distribution. 1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.7 The values stated in inch-pound units are to be regarded as standard. The values given in parenthe...

  2. 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.

  3. Residual Stress Formation Relating to Peak Temperature- and Austenite Grain Size-based Phase Transformation of S355 Steel

    Science.gov (United States)

    Klaproth, Fabian; Vollertsen, Frank

    Nowadays thermal forming processes of steel are state of the art in industrial applications. Nevertheless, the influences of thermal induced phase-transformation on residual stresses and strength have not been fully observed. Times needed for transformation are affected by the initial austenite grain size, while the prevailing peak temperature influences austenite grain growth. Higher temperatures lead to larger austenite grains, leading to increased times for transformation. In order to get an embraced understanding of such effects numerical simulations of phase-transformations are mandatory. In this paper simulations of thermal forming processes, using S355 steel, are presented. Different continuous-cooling-transformation-diagrams (cct-diagrams) of specific austenite grain sizes for temperatures between transformation point AC3 and melting temperature are implemented in the model. It is shown that resulting magnitudes of residual stresses vary between 248 N/mm2 and 550 N/mm2. Finally an approach for the impact on relevant peak temperatures in the heat affected zone is outlined.

  4. 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

  5. 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.

  6. 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.

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

    Digital Repository Service at National Institute of Oceanography (India)

    Valsangkar, A.B.; Fernandes, D.

    fractions from shallow depth (less than 5 m) during the SW monsoon and deposition in deeper depths (more than 10 m) during post-monsoon. It is further inferred that the E-W trending depression in the central part of the Bay partially controls the sand...

  8. Grain-size segregation and levee formation in geophysical mass flows

    Science.gov (United States)

    Johnson, C.G.; Kokelaar, B.P.; Iverson, Richard M.; Logan, M.; LaHusen, R.G.; Gray, J.M.N.T.

    2012-01-01

    Data from large-scale debris-flow experiments are combined with modeling of particle-size segregation to explain the formation of lateral levees enriched in coarse grains. The experimental flows consisted of 10 m3 of water-saturated sand and gravel, which traveled ∼80 m down a steeply inclined flume before forming an elongated leveed deposit 10 m long on a nearly horizontal runout surface. We measured the surface velocity field and observed the sequence of deposition by seeding tracers onto the flow surface and tracking them in video footage. Levees formed by progressive downslope accretion approximately 3.5 m behind the flow front, which advanced steadily at ∼2 m s−1during most of the runout. Segregation was measured by placing ∼600 coarse tracer pebbles on the bed, which, when entrained into the flow, segregated upwards at ∼6–7.5 cm s−1. When excavated from the deposit these were distributed in a horseshoe-shaped pattern that became increasingly elevated closer to the deposit termination. Although there was clear evidence for inverse grading during the flow, transect sampling revealed that the resulting leveed deposit was strongly graded laterally, with only weak vertical grading. We construct an empirical, three-dimensional velocity field resembling the experimental observations, and use this with a particle-size segregation model to predict the segregation and transport of material through the flow. We infer that coarse material segregates to the flow surface and is transported to the flow front by shear. Within the flow head, coarse material is overridden, then recirculates in spiral trajectories due to size-segregation, before being advected to the flow edges and deposited to form coarse-particle-enriched levees.

  9. Influence of grain size and sintering temperature grain size on the critical behavior near the paramagnetic to ferromagnetic phase transition temperature in La0.67Sr0.33MnO3 nanoparticles

    Science.gov (United States)

    Baaziz, H.; Tozri, A.; Dhahri, E.; Hlil, E. K.

    2018-03-01

    We have undertaken a systematic study of critical behavior in La0.67Sr0.33MnO3 nanoparticles, sintered at different temperatures (L6, L8, L10 and L12 sintered at 600 °C, 800 °C, 1000 °C, 1200 °C respectively), by magnetization measurements. The critical exponents are estimated by various techniques such as the Modified Arrott plot, Kouvel-Fisher plot and critical isotherm technique. Compared to standard models, the critical exponents are close to those expected by the Mean-field model (with β = 0.5 γ = 1, and δ = 3) for (L6, L8, and L10) samples and by the (3D) Heisenberg model (β = 0.365, γ = 1.336 and δ = 4.80) for L12 sample. We conclude that the reduction of grain size strongly influences the universality class.

  10. Different trends in extreme and median surface aerosol extinction coefficients over China inferred from quality-controlled visibility data

    Directory of Open Access Journals (Sweden)

    J. Li

    2018-03-01

    Full Text Available Although the temporal changes in aerosol properties have been widely investigated, the majority of studies has focused on average conditions without much emphasis on the extremes. However, the latter can be more important in terms of human health and climate change. This study uses a previously validated, quality-controlled visibility dataset to investigate the long-term trends (expressed in terms of relative changes in extreme surface aerosol extinction coefficient (AEC over China and compares them with the median trends. Two methods are used to independently evaluate the trends, which arrive at consistent results. The signs of extreme and median trends are generally coherent, whereas their magnitudes show distinct spatial and temporal differences. In the 1980s, an overall positive trend is found throughout China with the extreme trend exceeding the mean trend, except for northwest China and the North China Plain. In the 1990s, AEC over northeast and northwest China started to decline while the rest of the country still exhibited an increase. The extreme trends continued to dominate in the south while they yielded to the mean trend in the north. After the year 2000, the extreme trend became weaker than the mean trend overall in terms of both the magnitude and significance level. The annual trend can be primarily attributed to winter and fall trends. The results suggest that the decadal changes in pollution in China may be governed by different mechanisms. Synoptic conditions that often result in extreme air quality changes might have dominated in the 1980s, whereas emission increase might have been the main factor for the 2000s.

  11. Different trends in extreme and median surface aerosol extinction coefficients over China inferred from quality-controlled visibility data

    Science.gov (United States)

    Li, Jing; Li, Chengcai; Zhao, Chunsheng

    2018-03-01

    Although the temporal changes in aerosol properties have been widely investigated, the majority of studies has focused on average conditions without much emphasis on the extremes. However, the latter can be more important in terms of human health and climate change. This study uses a previously validated, quality-controlled visibility dataset to investigate the long-term trends (expressed in terms of relative changes) in extreme surface aerosol extinction coefficient (AEC) over China and compares them with the median trends. Two methods are used to independently evaluate the trends, which arrive at consistent results. The signs of extreme and median trends are generally coherent, whereas their magnitudes show distinct spatial and temporal differences. In the 1980s, an overall positive trend is found throughout China with the extreme trend exceeding the mean trend, except for northwest China and the North China Plain. In the 1990s, AEC over northeast and northwest China started to decline while the rest of the country still exhibited an increase. The extreme trends continued to dominate in the south while they yielded to the mean trend in the north. After the year 2000, the extreme trend became weaker than the mean trend overall in terms of both the magnitude and significance level. The annual trend can be primarily attributed to winter and fall trends. The results suggest that the decadal changes in pollution in China may be governed by different mechanisms. Synoptic conditions that often result in extreme air quality changes might have dominated in the 1980s, whereas emission increase might have been the main factor for the 2000s.

  12. 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

  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. Image - Rice Grain Scanner: a three-dimensional fully automated assessment of grain size and quality traits

    Directory of Open Access Journals (Sweden)

    Rubens Marschalek

    2016-12-01

    Full Text Available The Image is a scanner developed as a grain classifier for quality control at the rice industry based on Brazilian official norms. It orders the dehulled grains ensuring that each grain would pass individually, in free fall, while the grain is analysed from different sides, covering its whole surface. It ensures a precise three-dimensional measurement of grain size, chalkiness, defects of the grain, milling quality, given out a total of 39 traits/classes/defects/values, which are sent to a excel Microsoft spreadsheet. This is managed through a digital platform which analysis routine and layout were developed and designed by Selgron and Epagri to fit the needs of research. The scanner and its software reach outputs that enhance rice breeding efficiency for grain quality, performing it faster, precisely and with a high-throughput phenotyping than ever before, especially interesting in very early breeding generations.

  15. 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)

  16. Development of fine-grain size titanium 6Al–4V alloy sheet material for low temperature superplastic forming

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Tuoyang [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan (China); Liu, Yong, E-mail: yonliu@csu.edu.cn [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan (China); Sanders, Daniel G. [Boeing Research and Technology, Seattle, WA (United States); Liu, Bin; Zhang, Weidong; Zhou, Canxu [State Key Laboratory of Powder Metallurgy, Central South University, Changsha, Hunan (China)

    2014-07-01

    Fine-grained titanium 6Al–4V alloy, which typically has a grain size of about 1–2 μm, can be made to superplastic form at around 800 °C with special processing. The normal temperature for superplastic forming (SPF) with conventional titanium 6Al–4V sheet material is 900 °C. The lower temperature performance is of interest to the Boeing Company because it can be exploited to achieve significant cost savings in processing by reducing the high-temperature oxidation of the SPF dies, improving the heater rod life for the hot presses, increasing operator safety and replacing the chemical milling operation to remove alpha case contamination with a less intensive nitric hydrofluoric acid etchant (pickle). In this report, room temperature tensile tests and elevated temperature constant strain rate tensile tests of fine-grained Ti–6Al–4V sheets provided by the Baoti Company of Xi'an, China, were conducted according to the test method standards of ASTM-E8 and ASTM-E2448. The relationships among the processing parameters, microstructure and superplastic behavior have been analyzed. The results show that two of the samples produced met the Boeing minimum requirements for low-temperature superplasticity. The successful material was heat-treated at 800 °C subsequent to hot rolling above the beta transus temperature, T{sub β}-(150–250 °C). It was found that the sheet metal microstructure has a significant influence on superplastic formability of the Ti–6Al–4V alloy. Specifically, fine grains, a narrow grain size distribution, low grain aspect ratio and moderate β phase volume fraction can contribute to higher superplastic elongations.

  17. 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.

  18. Using grain-size characteristics to model soil water content: Application to dose-rate calculation for luminescence dating

    International Nuclear Information System (INIS)

    Nelson, Michelle S.; Rittenour, Tammy M.

    2015-01-01

    Soil moisture is an important factor for dose-rate determination in luminescence and other dating methods as soil water content impacts sediment bulk density, alters rates of chemical reactions and attenuates effective exposure to nuclear radiation from the surrounding sediments and incoming cosmic rays. Given its importance in dose-rate calculation, methods for measuring and modeling soil water content are discussed, with special focus on semi-arid environments and other situations where modern in situ values are unlikely to be representative of mean soil moisture conditions. We present an alternative method for calculating sediment water content based on grain-size characteristics using the freely available Rosetta Lite v.1.1 software. Modeled outputs include saturation, residual and other water retention curve (WRC) parameters. WRCs were generated from model outputs using the van Genuchten (1980) equation, and mean annual water state was determined using soil moisture regime maps and classifications. Dose-rate values using modeled outputs and laboratory-measured in situ and saturation water content are compared in a test case using Holocene alluvial sediments from Kanab Creek in southern Utah, USA. Best practices for how to estimate mean annual water state for different soil moisture regimes and past soil moisture content in situations where in situ values are not representative of the burial history are discussed. - Highlights: • Using grain size characteristics to generate water retention curves. • Saturation water content was estimated using laboratory and computer modeling. • In situ water content is compared with the model outputs. • Dose-rate variability with new water content estimates is evaluated.

  19. Transport of metabolically active bacteria in porous media:the effect of substrate, age, and grain size

    Science.gov (United States)

    Araujo, J. B.; Bradford, S. A.; Simunek, J.; Vereecken, H.; Klumpp, E.

    2008-12-01

    In our studies we sought to understand the biological processes affecting the microbial transport and retention of metabolically active Pseudomonas putida. To study the role of the metabolic state of the bacteria, we conducted a series of column experiments, varying saturation, substrate concentration, and grain size to help elucidate mechanisms present. Results show a significant difference between the metabolic state in the effluent, under unsaturated conditions, offset by grain-size effects. The presence of substrate appears to influence the breakthrough behavior of these cells in the smaller sand grains. We have also observed that the hydrophobicity of cells change according to their life-cycle. In addition we conducted a simple micro-model experiment, to observe if the cells behavior could be affected by their own motility. The results show that the cells travel with solution, suggesting that the flagella does not significantly contribute to movement through the porous media under these conditions. Furthermore, we monitored the cells in fresh batch solution and filtered solution under the microscope. In this case, we confirmed that during the stationary phase, when the cells are older there is an increased presence of aggregates, contrasting to the cells in the log-phase. There are also very long rod-shaped cells, which appear to undergo a process of cell division. The spatial distribution of these cells was also analyzed. The results indicate there are various mechanisms influencing the retention mechanisms of Pseudomonas putida, which are directly dependent on the metabolic state, substrate presence, and saturation of the porous media. The experimental data were analyzed using a mathematical model under a modified HYDRUS1D.

  20. Temporal and spatial variability of the sediment grain-size distribution on the Eel shelf: The flood layer of 1995

    Science.gov (United States)

    Drake, D.E.

    1999-01-01

    Sediment grain-size characteristics observed on the Eel shelf have been analyzed using a wet-sieving technique that minimizes breakage of aggregates. At several sites on the 70-m isobath north of the river, where a 1995 flood layer attained a maximum thickness of about 9 cm, replicate box cores were collected on seven cruises during February 1995 to January 1997. These samples provide a unique opportunity to follow the evolution of a flood layer over a two-year period as it was modified and gradually buried. One month after the flood, a layer of tan-colored, high-porosity sediment with up to 96% of its particles in the size range of 0-20 ??m had accumulated on the central part of the shelf, 7-30 km north of the river and principally between the 50-m and 90-m isobaths. Substantial coarsening of this layer occurred between February 1995 and May 1995, particularly along the southern and the landward edge of the deposit in water depths of <70 m. The early stage of coarsening was probably caused by physical reworking of the surface 0.5-cm of the deposit and by addition of new sediment from shallower regions of the shelf. Temporal changes in inventories of several grain-size fractions show that physical processes continued to add coarse sediment to the flood layer after May 1995, but the large increases in thickness of the surface mixed layer could only be attributed to bioturbation by a recovering, or seasonally fluctuating, benthic community. The 1995 flood layer has evolved from exhibiting limited variability and normal grading (i:e., upward fining) to a layer that (1) shows significant spatial variability on scales from centimeters to 10's of meters, (2) is substantially coarser owing to additions of sediment from the inner shelf, (3) is inversely graded (i.e., coarsens upward), and (4) is intensely bioturbated to depths of 4-5 cm.

  1. 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.

  2. [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.

  3. Development of fine-grain size titanium 6Al–4V alloy sheet material for low temperature superplastic forming

    International Nuclear Information System (INIS)

    Zhang, Tuoyang; Liu, Yong; Sanders, Daniel G.; Liu, Bin; Zhang, Weidong; Zhou, Canxu

    2014-01-01

    Fine-grained titanium 6Al–4V alloy, which typically has a grain size of about 1–2 μm, can be made to superplastic form at around 800 °C with special processing. The normal temperature for superplastic forming (SPF) with conventional titanium 6Al–4V sheet material is 900 °C. The lower temperature performance is of interest to the Boeing Company because it can be exploited to achieve significant cost savings in processing by reducing the high-temperature oxidation of the SPF dies, improving the heater rod life for the hot presses, increasing operator safety and replacing the chemical milling operation to remove alpha case contamination with a less intensive nitric hydrofluoric acid etchant (pickle). In this report, room temperature tensile tests and elevated temperature constant strain rate tensile tests of fine-grained Ti–6Al–4V sheets provided by the Baoti Company of Xi'an, China, were conducted according to the test method standards of ASTM-E8 and ASTM-E2448. The relationships among the processing parameters, microstructure and superplastic behavior have been analyzed. The results show that two of the samples produced met the Boeing minimum requirements for low-temperature superplasticity. The successful material was heat-treated at 800 °C subsequent to hot rolling above the beta transus temperature, T β -(150–250 °C). It was found that the sheet metal microstructure has a significant influence on superplastic formability of the Ti–6Al–4V alloy. Specifically, fine grains, a narrow grain size distribution, low grain aspect ratio and moderate β phase volume fraction can contribute to higher superplastic elongations

  4. 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.

  5. Interaction of Kuroshio Current with Global Oceanic and Atmospheric Circulations: Evidences of Grain Size from Okinawa Trough

    Science.gov (United States)

    Wang, J.; Li, A.; Xu, K.; Huang, J.

    2016-12-01

    Okinawa Trough is an ideal place for the study of paleoceanography and paleoenvironment changes. However, the provenances of the sediments and paleoenvironment evolution of the Okinawa Trough have still not been settled yet. Based on grain size, clay minerals and AMS 14C data of the Core OKI03, the provenances and paleoenvironemnt evolution in the middle Okinawa Trough during the last 8 ka were studied. The results indicate that terrigenous sediments deposited in the middle Okinawa Trough were mainly from Yangtze River and Taiwanese rivers since 8 ka. Kuroshio Current (KC), a Western Pacific Ocean boundary current, flows into Okinawa Trough by eastern Taiwan Island, and influences the sediments delivery and distribution within the trough, and also impact the regional and local marine environment in adjacent seas. Statistics study of high resolution grain size in the trough recognizes a millennial-scale oscillation (center around 1800 yr) and a centennial-scale oscillation (center around 512 yr) for KC evolution since last 8 ka. The millennial-scale oscillation is probably related to the North Atlantic Deep Water production with 1400-yr time lag, via the mixing upwelling and impacts on the sea surface temperature (SST) in equatorial Pacific. Meanwhile, the centennial-scale variation possibly corresponds to the solar irradiation with a 240-yr time uncertainty, through the SST change. KC possible influences the climate and North Atlantic Deep Water formation by transferring heat to the atmosphere in high latitude of Pacific Ocean, and also interacts with the thermohaline circulation by transferring heat to Indian Ocean through North Pacific Intermediate Water.

  6. 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

  7. Analysis of the Grain Size Evolution for Ferrite Formation in Fe-C-Mn Steels Using a 3D Model Under a Mixed-Mode Interface Condition

    Science.gov (United States)

    Fang, H.; Mecozzi, M. G.; Brück, E.; van der Zwaag, S.; van Dijk, N. H.

    2018-01-01

    A 3D model has been developed to predict the average ferrite grain size and grain size distribution for an austenite-to-ferrite phase transformation during continuous cooling of an Fe-C-Mn steel. Using a Voronoi construction to represent the austenite grains, the ferrite is assumed to nucleate at the grain corners and to grow as spheres. Classical nucleation theory is used to estimate the density of ferrite nuclei. By assuming a negligible partition of manganese, the moving ferrite-austenite interface is treated with a mixed-mode model in which the soft impingement of the carbon diffusion fields is considered. The ferrite volume fraction, the average ferrite grain size, and the ferrite grain size distribution are derived as a function of temperature. The results of the present model are compared with those of a published phase-field model simulating the ferritic microstructure evolution during linear cooling of an Fe-0.10C-0.49Mn (wt pct) steel. It turns out that the present model can adequately reproduce the phase-field modeling results as well as the experimental dilatometry data. The model presented here provides a versatile tool to analyze the evolution of the ferrite grain size distribution at low computational costs.

  8. 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.

  9. High frequency compressional wave speed and attenuation measurements in water-saturated granular media with unimodal and bimodal grain size distributions.

    Science.gov (United States)

    Yang, Haesang; Seong, Woojae

    2018-02-01

    Compressional wave speed and attenuation were measured for water-saturated granular media employing five kinds of glass beads having unimodal and bimodal grain size distributions. Glass beads with grain sizes ranging from 250 to 850  μm were used for the acoustic measurements at a frequency range from 350 kHz to 1.1 MHz, which includes the transition range where scattering and non-scattering losses co-exist. The compressional wave speed and attenuation data are presented as a function of frequency and grain size distribution. The compressional wave speed and attenuation data show a variety of frequency dependencies for varying grain size distribution. The observed acoustic properties are investigated for the volume ratio of larger and smaller sized grains in the mixed bimodal media. Also, the measured results are compared with the empirical multiple scattering formula as a function of Rayleigh parameter  kd (product of wavenumber in the water k and mean grain diameter of the glass beads d) using weighted mean grain size. The measured results are also discussed, focusing on the geophysical difference between unimodal and bimodal mixed grains.

  10. Techniques for Mitigating Thermal Fatigue Degradation, Controlling Efficiency, and Extending Lifetime in a ZnO Thermoelectric Using Grain Size Gradient FGMs

    Science.gov (United States)

    Cramer, Corson L.; Li, Wenjie; Jin, Zhi-He; Wang, Jue; Ma, Kaka; Holland, Troy B.

    2018-01-01

    A functionally graded material (FGM) in terms of grain size gradation is fabricated using zinc oxide (ZnO) with spark plasma sintering and an additive manufacturing technique by diffusion bonding layers of material sintered at different temperatures to achieve a thermoelectric generator (TEG) material that can dissipate heat well and retain high energy conversion efficiency for longer-lasting and comparably efficient TEGs. This FGM is compared to a previously made FGM with continuous grain size gradation. Uniform and graded grain size conditions are modeled for thermoelectric output by using thermoelectric properties of the uniform grain size as well as the varying properties seen in the FGMs. The actual thermoelectric output of the samples is measured and compared to the simulations. The grain size has a large effect on the efficiency and efficiency range. The samples are thermally cycled with a fast heating rate to test the thermal stress robustness and degradation, and the resistance at the highest temperature is measured to indicate degradation from thermal stress. The measured efficiency after cycling shows that the FGMs survive longer lifetime than that with uniform small grains.

  11. Effect of texture and grain size on the magnetic flux density and core loss of cold-rolled high silicon steel sheets

    Science.gov (United States)

    Qin, Jing; Yang, Ping; Mao, Weimin; Ye, Feng

    2015-11-01

    The effects of texture and grain size on the magnetic flux density and core loss (50-20 kHz) of 0.23 mm-thick cold-rolled high silicon steel sheets are investigated by means of electron back-scattered diffraction (EBSD), loss separation, and anisotropy parameter (ε) calculation. A model of the hysteresis loss coefficient kh considering average grain size and ε is established. The magnetic flux density at 800 A/m (B8) is closely related to the volume fraction of η-fiber-oriented grains, while the magnetic flux density at 5000 A/m (B50) is closely related to the volume fractions of γ- and λ-fiber-oriented grains in high silicon steel. The hysteresis loss of high silicon steel can be greatly reduced by increasing the grain size and optimizing the texture of the sheets. Although increases in frequencies decrease the effect of texture on core loss, the effect cannot be ignored. As annealing temperature and time increase, the relative difference in core loss between the rolling direction (RD) and the transverse direction (TD) is maintained at higher frequencies because of increases in grain size, decreases in γ texture, and maintenance of a strong η texture. Texture and grain size jointly affect the high-frequency core loss of high silicon steel.

  12. Localized melt-scan strategy for site specific control of grain size and primary dendrite arm spacing in electron beam additive manufacturing

    Energy Technology Data Exchange (ETDEWEB)

    Raghavan, Narendran; Simunovic, Srdjan; Dehoff, Ryan; Plotkowski, Alex; Turner, John; Kirka, Michael; Babu, Suresh

    2017-11-01

    In addition to design geometry, surface roughness, and solid-state phase transformation, solidification microstructure plays a crucial role in controlling the performance of additively manufactured components. Crystallographic texture, primary dendrite arm spacing (PDAS), and grain size are directly correlated to local solidification conditions. We have developed a new melt-scan strategy for inducing site specific, on-demand control of solidification microstructure. We were able to induce variations in grain size (30 μm–150 μm) and PDAS (4 μm - 10 μm) in Inconel 718 parts produced by the electron beam additive manufacturing system (Arcam®). A conventional raster melt-scan resulted in a grain size of about 600 μm. The observed variations in grain size with different melt-scan strategies are rationalized using a numerical thermal and solidification model which accounts for the transient curvature of the melt pool and associated thermal gradients and liquid-solid interface velocities. The refinement in grain size at high cooling rates (>104 K/s) is also attributed to the potential heterogeneous nucleation of grains ahead of the epitaxially growing solidification front. The variation in PDAS is rationalized using a coupled numerical-theoretical model as a function of local solidification conditions (thermal gradient and liquid-solid interface velocity) of the melt pool.

  13. Black Carbon Aerosol in Rome (Italy: Inference of a Long-Term (2001–2017 Record and Related Trends from AERONET Sun-Photometry Data

    Directory of Open Access Journals (Sweden)

    Antonio Di Ianni

    2018-02-01

    Full Text Available Surface concentration of black carbon (BC is a key factor for the understanding of the impact of anthropogenic pollutants on human health. The majority of Italian cities lack long-term measurements of BC concentrations since such a metric is not regulated by EU legislation. This work attempts a long-term (2001–2017 inference of equivalent black carbon (eBC concentrations in the city of Rome (Italy based on sun-photometry data. To this end, aerosol light absorption coefficients at the surface are inferred from the ”columnar” aerosol aerosol light absorption coefficient records from the Rome Tor Vergata AERONET sun-photometer. The main focus of this work is to rescale aerosol light absorption columnar data (AERONET to ground-level BC data. This is done by using values of mixing layer height (MLH derived from ceilometer measurements and then by converting the absorption into eBC mass concentration through a mass–to–absorption conversion factor, the Mass Absorption Efficiency (MAE. The final aim is to obtain relevant data representative of the BC aerosol at the surface (i.e., in-situ–so within the MLH– and then to infer a long-term record of “surface” equivalent black carbon mass concentration in Rome. To evaluate the accuracy of this procedure, we compared the AERONET-based results to in-situ measurements of aerosol light absorption coefficients ( α abs collected during some intensive field campaigns performed in Rome between 2010 and 2017. This analysis shows that different measurement methods, local emissions, and atmospheric conditions (MLH, residual layers are some of the most important factors influencing differences between inferred and measured α abs. As a general result, ”inferred” and ”measured” α abs resulted to reach quite a good correlation (up to r = 0.73 after a screening procedure that excludes one of the major cause of discrepancy between AERONET inferred and in-situ measured α abs: the presence of

  14. A generative inference framework for analysing patterns of cultural change in sparse population data with evidence for fashion trends in LBK culture.

    Science.gov (United States)

    Kandler, Anne; Shennan, Stephen

    2015-12-06

    Cultural change can be quantified by temporal changes in frequency of different cultural artefacts and it is a central question to identify what underlying cultural transmission processes could have caused the observed frequency changes. Observed changes, however, often describe the dynamics in samples of the population of artefacts, whereas transmission processes act on the whole population. Here we develop a modelling framework aimed at addressing this inference problem. To do so, we firstly generate population structures from which the observed sample could have been drawn randomly and then determine theoretical samples at a later time t2 produced under the assumption that changes in frequencies are caused by a specific transmission process. Thereby we also account for the potential effect of time-averaging processes in the generation of the observed sample. Subsequent statistical comparisons (e.g. using Bayesian inference) of the theoretical and observed samples at t2 can establish which processes could have produced the observed frequency data. In this way, we infer underlying transmission processes directly from available data without any equilibrium assumption. We apply this framework to a dataset describing pottery from settlements of some of the first farmers in Europe (the LBK culture) and conclude that the observed frequency dynamic of different types of decorated pottery is consistent with age-dependent selection, a preference for 'young' pottery types which is potentially indicative of fashion trends. © 2015 The Author(s).

  15. A Dislocation-Based Theory for the Deformation Hardening Behavior of DP Steels: Impact of Martensite Content and Ferrite Grain Size

    Directory of Open Access Journals (Sweden)

    Yngve Bergström

    2010-01-01

    Full Text Available A dislocation model, accurately describing the uniaxial plastic stress-strain behavior of dual phase (DP steels, is proposed and the impact of martensite content and ferrite grain size in four commercially produced DP steels is analyzed. It is assumed that the plastic deformation process is localized to the ferrite. This is taken into account by introducing a nonhomogeneity parameter, f(ε, that specifies the volume fraction of ferrite taking active part in the plastic deformation process. It is found that the larger the martensite content the smaller the initial volume fraction of active ferrite which yields a higher initial deformation hardening rate. This explains the high energy absorbing capacity of DP steels with high volume fractions of martensite. Further, the effect of ferrite grain size strengthening in DP steels is important. The flow stress grain size sensitivity for DP steels is observed to be 7 times larger than that for single phase ferrite.

  16. 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

  17. Effect of texture and grain size on the magnetic flux density and core loss of cold-rolled high silicon steel sheets

    International Nuclear Information System (INIS)

    Qin, Jing; Yang, Ping; Mao, Weimin; Ye, Feng

    2015-01-01

    The effects of texture and grain size on the magnetic flux density and core loss (50–20 kHz) of 0.23 mm-thick cold-rolled high silicon steel sheets are investigated by means of electron back-scattered diffraction (EBSD), loss separation, and anisotropy parameter (ε) calculation. A model of the hysteresis loss coefficient k h considering average grain size and ε is established. The magnetic flux density at 800 A/m (B 8 ) is closely related to the volume fraction of η-fiber-oriented grains, while the magnetic flux density at 5000 A/m (B 50 ) is closely related to the volume fractions of γ- and λ-fiber-oriented grains in high silicon steel. The hysteresis loss of high silicon steel can be greatly reduced by increasing the grain size and optimizing the texture of the sheets. Although increases in frequencies decrease the effect of texture on core loss, the effect cannot be ignored. As annealing temperature and time increase, the relative difference in core loss between the rolling direction (RD) and the transverse direction (TD) is maintained at higher frequencies because of increases in grain size, decreases in γ texture, and maintenance of a strong η texture. Texture and grain size jointly affect the high-frequency core loss of high silicon steel. - Highlights: • A model of hysteresis loss coefficient considering anisotropy parameter is obtained. • Effect of texture on high-frequency core loss of high-silicon steel cannot be ignored. • Texture and grain size jointly affect high-frequency core loss of high-silicon steel

  18. Effect of texture and grain size on the magnetic flux density and core loss of cold-rolled high silicon steel sheets

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Jing [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Yang, Ping, E-mail: yangp@mater.ustb.edu.cn [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); Mao, Weimin [School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Ye, Feng [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2015-11-01

    The effects of texture and grain size on the magnetic flux density and core loss (50–20 kHz) of 0.23 mm-thick cold-rolled high silicon steel sheets are investigated by means of electron back-scattered diffraction (EBSD), loss separation, and anisotropy parameter (ε) calculation. A model of the hysteresis loss coefficient k{sub h} considering average grain size and ε is established. The magnetic flux density at 800 A/m (B{sub 8}) is closely related to the volume fraction of η-fiber-oriented grains, while the magnetic flux density at 5000 A/m (B{sub 50}) is closely related to the volume fractions of γ- and λ-fiber-oriented grains in high silicon steel. The hysteresis loss of high silicon steel can be greatly reduced by increasing the grain size and optimizing the texture of the sheets. Although increases in frequencies decrease the effect of texture on core loss, the effect cannot be ignored. As annealing temperature and time increase, the relative difference in core loss between the rolling direction (RD) and the transverse direction (TD) is maintained at higher frequencies because of increases in grain size, decreases in γ texture, and maintenance of a strong η texture. Texture and grain size jointly affect the high-frequency core loss of high silicon steel. - Highlights: • A model of hysteresis loss coefficient considering anisotropy parameter is obtained. • Effect of texture on high-frequency core loss of high-silicon steel cannot be ignored. • Texture and grain size jointly affect high-frequency core loss of high-silicon steel.

  19. 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

  20. 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.

  1. A single-nucleotide polymorphism causes smaller grain size and loss of seed shattering during African rice domestication.

    Science.gov (United States)

    Wu, Wenguang; Liu, Xiaoyun; Wang, Muhua; Meyer, Rachel S; Luo, Xiaojin; Ndjiondjop, Marie-Noelle; Tan, Lubin; Zhang, Jianwei; Wu, Jianzhong; Cai, Hongwei; Sun, Chuanqing; Wang, Xiangkun; Wing, Rod A; Zhu, Zuofeng

    2017-05-08

    Grain size is one of the most important components of grain yield and selecting large seeds has been a main target during plant domestication. Surprisingly, the grain of African cultivated rice (Oryza glaberrima Steud.) typically is smaller than that of its progenitor, Oryza barthii. Here we report the cloning and characterization of a quantitative trait locus, GL4, controlling the grain length on chromosome 4 in African rice, which regulates longitudinal cell elongation of the outer and inner glumes. Interestingly, GL4 also controls the seed shattering phenotype like its orthologue SH4 gene in Asian rice. Our data show that a single-nucleotide polymorphism (SNP) mutation in the GL4 gene resulted in a premature stop codon and led to small seeds and loss of seed shattering during African rice domestication. These results provide new insights into diverse domestication practices in African rice, and also pave the way for enhancing crop yield to meeting the challenge of cereal demand in West Africa.

  2. U-Th-Ra variations in Himalayan river sediments (Gandak river, India): Weathering fractionation and/or grain-size sorting?

    Science.gov (United States)

    Bosia, Clio; Chabaux, François; Pelt, Eric; France-Lanord, Christian; Morin, Guillaume; Lavé, Jérôme; Stille, Peter

    2016-11-01

    Understanding the origin of U-Th-Ra variations in the Ganga river sediments is a prerequisite for correctly using U-series nuclides to constrain the sediment transport times in Himalayan rivers. For this purpose, U, Th, and Ra concentrations, along with 238U-234U-230Th-226Ra radioactive disequilibria, were analyzed in bank, bedload and suspended sediments from the Gandak river, one of the main tributaries of the Ganga river. The data confirm that U and Th budgets of the Himalayan sediments are significantly influenced by minor resistant minerals, such as zircon, garnet and Ti-bearing minerals, the dissolution of which required the use of a high-pressure acid digestion process. Most importantly, the results indicate that the variations in (238U/232Th) and (230Th/232Th) activity ratios and 238U-234U-230Th-226Ra disequilibria in sediments along the river alluvial plain mainly reflect modifications in the mineralogical and grain-size compositions rather than the degree of weathering during transport. The (238U/232Th) and (230Th/232Th) activity ratios in the bank and bed sediments are related to variations in the minor primary minerals strongly enriched in U and Th (i.e., zircon, REE-bearing minerals and Ti-bearing minerals), whereas the activity ratios in the suspended load are related to variations in the proportions of clay, Fe-oxyhydroxides and the silt-sand fraction, which contains U- and Th-bearing minor minerals. The data also indicate that 238U-234U-230Th-226Ra disequilibria are strongly influenced by secondary mineral phases: the 230Th budget is likely mainly controlled by Fe-oxyhydroxides, and the 226Ra budget is likely mainly controlled by clay minerals. Therefore, the variations in the 238U-234U-230Th-232Th system in the sediments of the Gandak river cannot simply be interpreted as the result of fractionation due to chemical transformation of the bulk sediment during its transport within the alluvial plain and/or the result of radioactive decay. Consequently

  3. Pleistocene climate change inferred from multi-proxy analyses of a loess-paleosol sequence in China

    Science.gov (United States)

    Wu, Yi; Qiu, Shifan; Fu, Shuqing; Rao, Zhiguo; Zhu, Zhaoyu

    2018-04-01

    The aeolian loess blanketing the Chinese Loess Plateau (CLP) is sensitive to climate change in monsoonal East Asia. Here, we present a multi-proxy climatic record from a Pleistocene loess-paleosol sequence from the Lantian Basin on the southern margin of the CLP. The measurements include magnetic susceptibility and related magnetic properties, bulk median grain-size, color reflectance, and the color-inferred hematite versus goethite ratio (Hm/Gt). A long-term aridification and cooling trend during the interval from ca 2.22-0.43 Ma is indicated by two magnetic grain-size proxies, corresponding to the global climatic cooling of the late Cenozoic. In addition, at least four intervals of climatic extremes are evident in the record of Hm/Gt ratio: at 1.71-1.65 Ma, 1.26-1.24 Ma, 0.94-0.86 Ma, and 0.62-0.48 Ma. These intervals are characterized by distinct regional climates, which contrast with the global climatic conditions represented in marine sediments. For example, a relatively arid climate is documented from 1.71 to 1.65 Ma, which was rapidly succeeded by a relatively humid climate which is associated with the earliest hominin (with an age of ca 1.63 Ma) in the Lantian Basin.

  4. 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...

  5. 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

  6. Magnetic properties of natural pyrrhotite.II. High- and low-temperature behaviour of ~and TRM as function of grain size

    NARCIS (Netherlands)

    Dekkers, M.J.

    1989-01-01

    Twelve grain-size fractions, ranging from 250 ~tm down to <5 ~m, of four natural pyrrhotite samples were homogeneously dispersed in a non-magnetic matrix to study their magnetic behaviour during thermal demagnetization and low-temperature treatment. Normalized decay curves of the isothermal

  7. 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

  8. Tamanho de grão comercial em cultivares de feijoeiro Commercial grain size in common bean cultivars

    Directory of Open Access Journals (Sweden)

    Sérgio Augusto Morais Carbonell

    2010-10-01

    Full Text Available Os objetivos do trabalho foram avaliar e indicar parâmetros de seleção para classificação de grãos de feijão que atendam as exigências do mercado consumidor. Foram instalados experimentos contendo 19 genótipos de feijoeiro em nove ambientes, no Estado de São Paulo. A produção de grãos foi estratificada em peneiras de classificação 10 (10/64" pol. a 15 (15/64" pol. e avaliada a produção relativa de grãos em peneiras 13 e 14, rendimento de peneira, massa de 1.000 grãos, tamanho de grãos e para os índices J=perfil e H=forma do grão. A produção relativa de grãos, rendimento de peneira, forma e perfil foram as características que apresentaram diferenças estatísticas significativas, indicando presença de variabilidade genética. Por meio da comparação dos resultados com testemunhas de feijoeiro já recomendadas para o setor produtivo, conclui-se que uma cultivar de feijoeiro deve apresentar alta massa de 1.000 grãos (251 a 300g, produção relativa de grãos em peneiras 13 e 14 com valores acima de sete, rendimento de peneira acima de 70,0% e também sementes elípticas e perfil semiachatado.The aim of this research was to evaluate and to direct the genetic parameters to classify the grain size of common bean, according to the market demand. Experiments with 19 common bean genotypes were assembled in nine sites in the São Paulo State. The grain yield was stratified following sieve classification 10 (10/64" inch to 15 (15/64" inch. The following parameters were evaluated: relative yield with 13 and 14 sieves, sieve yield, thousand grain weight, grain size, J and H indexes (J=grain profile; H=grain shape. The relative grain yield, sieve yield, shapes and grain profiles presented significant statistical differences, indicating the presence of genetic variability among the genotypes. Compared to the market recommended and productive checks, the results showed that a common bean cultivar should present high thousand grain

  9. Evolutionary Insights Based on SNP Haplotypes of Red Pericarp, Grain Size and Starch Synthase Genes in Wild and Cultivated Rice

    Directory of Open Access Journals (Sweden)

    Nisha Singh

    2017-06-01

    Full Text Available The origin and domestication of rice has been a subject of considerable debate in the post-genomic era. Rice varieties have been categorized based on isozyme and DNA markers into two broad cultivar groups, Indica and Japonica. Among other well-known cultivar groups Aus varieties are closer to Indica and Aromatic varieties including Basmati are closer to Japonica, while deep-water rice varieties share kinship to both Indica and Japonica cultivar groups. Here, we analyzed haplotype networks and phylogenetic relationships in a diverse set of genotypes including Indian Oryza nivara/Oryza rufipogon wild rice accessions and representative varieties of four rice cultivar groups based on pericarp color (Rc, grain size (GS3 and eight different starch synthase genes (GBSSI, SSSI, SSIIa, SSIIb, SSIIIa, SSIIIb, SSIVa, and SSIVb. Aus cultivars appear to have the most ancient origin as they shared the maximum number of haplotypes with the wild rice populations, while Indica, Japonica and Aromatic cultivar groups showed varying phylogenetic origins of these genes. Starch synthase genes showed higher variability in cultivated rice than wild rice populations, suggesting diversified selection during and after domestication. O. nivara/O. rufipogon wild rice accessions belonging to different sub-populations shared common haplotypes for all the 10 genes analyzed. Our results support polyphyletic origin of cultivated rice with a complex pattern of migration of domestication alleles from wild to different rice cultivar groups. The findings provide novel insights into evolutionary and domestication history of rice and will help utilization of wild rice germplasm for genetic improvement of rice cultivars.

  10. Evolutionary Insights Based on SNP Haplotypes of Red Pericarp, Grain Size and Starch Synthase Genes in Wild and Cultivated Rice.

    Science.gov (United States)

    Singh, Nisha; Singh, Balwant; Rai, Vandna; Sidhu, Sukhjeet; Singh, Ashok K; Singh, Nagendra K

    2017-01-01

    The origin and domestication of rice has been a subject of considerable debate in the post-genomic era. Rice varieties have been categorized based on isozyme and DNA markers into two broad cultivar groups, Indica and Japonica. Among other well-known cultivar groups Aus varieties are closer to Indica and Aromatic varieties including Basmati are closer to Japonica, while deep-water rice varieties share kinship to both Indica and Japonica cultivar groups. Here, we analyzed haplotype networks and phylogenetic relationships in a diverse set of genotypes including Indian Oryza nivara/Oryza rufipogon wild rice accessions and representative varieties of four rice cultivar groups based on pericarp color ( Rc ), grain size ( GS3 ) and eight different starch synthase genes ( GBSSI, SSSI, SSIIa, SSIIb, SSIIIa, SSIIIb, SSIVa , and SSIVb ). Aus cultivars appear to have the most ancient origin as they shared the maximum number of haplotypes with the wild rice populations, while Indica, Japonica and Aromatic cultivar groups showed varying phylogenetic origins of these genes. Starch synthase genes showed higher variability in cultivated rice than wild rice populations, suggesting diversified selection during and after domestication. O. nivara/O. rufipogon wild rice accessions belonging to different sub-populations shared common haplotypes for all the 10 genes analyzed. Our results support polyphyletic origin of cultivated rice with a complex pattern of migration of domestication alleles from wild to different rice cultivar groups. The findings provide novel insights into evolutionary and domestication history of rice and will help utilization of wild rice germplasm for genetic improvement of rice cultivars.

  11. Monthly trends of methane emissions in Los Angeles from 2011 to 2015 inferred by CLARS-FTS observations

    Directory of Open Access Journals (Sweden)

    C. K. Wong

    2016-10-01

    Full Text Available This paper presents an analysis of methane emissions from the Los Angeles Basin at monthly timescales across a 4-year time period – from September 2011 to August 2015. Using observations acquired by a ground-based near-infrared remote sensing instrument on Mount Wilson, California, combined with atmospheric CH4–CO2 tracer–tracer correlations, we observed −18 to +22 % monthly variability in CH4 : CO2 from the annual mean in the Los Angeles Basin. Top-down estimates of methane emissions for the basin also exhibit significant monthly variability (−19 to +31 % from annual mean and a maximum month-to-month change of 47 %. During this period, methane emissions consistently peaked in the late summer/early fall and winter. The estimated annual methane emissions did not show a statistically significant trend over the 2011 to 2015 time period.

  12. [Grain Size Distribution Characteristics of Suspended Particulate Matter as Influenced by the Apparent Pollution in the Eutrophic Urban Landscape Water Body].

    Science.gov (United States)

    Gong, Dan-yan; Pan, Yang; Huang, Yong; Bao, Wei; Li, Qian-qian

    2016-03-15

    Grain size distribution characteristics of suspended particulate matter (SPM) reflects the apparent polluted condition of the urban landscape water. In order to explore the internal relationship between the eutrophication of urban landscape water's apparent pollution and grain size distribution of SPM, and its influencing factors, this paper selected five representative sampling sites in Feng Jin River which is a typical eutrophication river in Suzhou City, measured the grain size distribution of SPM, sensation pollution index (SPI) and water quality index, and analyzed their correlation. The results showed that: The rich nutrient water possessed a similar characteristics in grain size distribution. The grain size distribution of SPM in water was multimodal, and the the peak position was roughly the same; the grain size distribution of SPM was composed by multiple components. It could be roughly divided into six parts with the particle size range of every group being 516 µm. The component III was superior (with an average volume fraction of 38.3%-43.2%), and its volume fraction had a significant positive relation with the SPI value and the Chl-a content. The increase of component III volume fraction was the reflection of particle size's result of increasing SPI value. The increase of component III volume fraction was mainly derived from the increasing algal content. The volume fraction of group IV + group VI + group V was significantly higher under the condition of exogenous enter. When there was no exogenous component, the volume fraction of group IV + group VI + group V had a significant negative correlation with SPI value; when there were exogenous components, the volume fraction of group IV + group VI + group V had a weak positive correlation with SPI value, but the correlation did not reach a significant level. Environmental factors (Fv/Fm and DO) and exogenous factors had an influence by functioning on the algal content which signified the polluted material

  13. Atmospheric trends and radiative forcings of CF4 and C2F6 inferred from firn air.

    Science.gov (United States)

    Worton, David R; Sturges, William T; Gohar, Laila K; Shine, Keith P; Martinerie, Patricia; Oram, David E; Humphrey, Stephen P; Begley, Paul; Gunn, Lara; Barnola, Jean-Marc; Schwander, Jakob; Mulvaney, Robert

    2007-04-01

    The atmospheric histories of two potent greenhouse gases, tetrafluoromethane (CF4) and hexafluoroethane (C2F6), have been reconstructed for the 20th century based on firn air measurements from both hemispheres. The reconstructed atmospheric trends show that the mixing ratios of both CF4 and C2F6 have increased during the 20th century by factors of approximately 2 and approximately 10, respectively. Initially, the increasing mixing ratios coincided with the rise in primary aluminum production. However, a slower atmospheric growth rate for CF4 appears to be evident during the 1990s, which supports recent aluminum industry reports of reduced CF4 emissions. This work illustrates the changing relationship between CF4 and C2F6 that is likely to be largely the result of both reduced emissions from the aluminum industry and faster growing emissions of C2F6 from the semiconductor industry. Measurements of C2F6 in the older firn air indicate a natural background mixing ratio of <0.3 parts per trillion (ppt), demonstrating that natural sources of this gas are negligible. However, CF4 was deduced to have a preindustrial mixing ratio of 34 -1 ppt (-50% of contemporary levels). This is in good agreement with the previous work of Harnisch et al. (18) and provides independent confirmation of their results. As a result of the large global warming potentials of CF4 and C2F6, these results have important implications for radiative forcing calculations. The radiative forcings of CF4 and C2F6 are shown to have increased over the past 50 years to values in 2001 of 4.1 x 10(-3) Wm(-2) and 7.5 x 10(-4) Wm(-2), respectively, relative to preindustrial concentrations. These forcings are small compared to present day forcings due to the major greenhouse gases but, if the current trends continue, they will continue to increase since both gases have essentially infinite lifetimes. There is, therefore, a large incentive to reduce perfluorocarbon emissions such that through the implementation of

  14. 20th century trends and budget implications of chloroform and related tri-and dihalomethanes inferred from firn air

    Directory of Open Access Journals (Sweden)

    D. R. Worton

    2006-01-01

    Full Text Available Four trihalomethane (THM; CHCl3, CHBrCl2, CHBr2Cl and CHBr3 and two dihalomethane (DHM; CH2BrCl and CH2Br2 trace gases have been measured in air extracted from polar firn collected at the North Greenland Icecore Project (NGRIP site. CHCl3 was also measured in firn air from Devon Island (DI, Canada, Dronning Maud Land (DML, Antarctica and Dome Concordia (Dome C, Antarctica. All of these species are believed to be almost entirely of natural origin except for CHCl3 where anthropogenic sources have been reported to contribute ~10% to the global burden. A 2-D atmospheric model was run for CHCl3 using reported emission estimates to produce historical atmospheric trends at the firn sites, which were then input into a firn diffusion model to produce concentration depth profiles that were compared against the measurements. The anthropogenic emissions were modified in order to give the best model fit to the firn data at NGRIP, Dome C and DML. As a result, the contribution of CHCl3 from anthropogenic sources, mainly from pulp and paper manufacture, to the total chloroform budget appears to have been considerably underestimated and was likely to have been close to ~50% at the maximum in atmospheric CHCl3 concentrations around 1990, declining to ~29% at the beginning of the 21st century. We also show that the atmospheric burden of the brominated THM's in the Northern Hemisphere have increased over the 20th century while CH2Br2 has remained constant over time implying that it is entirely of natural origin.

  15. Grain size tuning of nanostructured Cu{sub 2}O films through vapour phase supersaturation control and their characterization for practical applications

    Energy Technology Data Exchange (ETDEWEB)

    Anu, A.; Abdul Khadar, M., E-mail: mabdulkhadar@rediffmail.com [Centre for Nanoscience and Nanotechnology, University of Kerala, Kariavattom, Thiruvananthapuram - 695 581, Kerala (India)

    2015-09-15

    A strategy for creating nanostructured films is the alignment of nanoparticles into ordered superstructures as living organisms synthesize biomaterials with superior physical properties using nanoparticle building blocks. We synthesized nanostructured films of Cu{sub 2}O of variable grain size by establishing the condition of supersaturation for creation of nanoparticles of copper which deposited as nanograined films and which was then oxidized. This technique has the advantage of being compatible with conventional vacuum processes for electronic device fabrication. The Cu{sub 2}O film samples consisted of a secondary structure of spherical particles of almost uniform size, each particle being an agglomerate of primary nanocrystals. Fractal analysis of the AFM images of the samples is carried out for studying the aggregation mechanism. Grain size tuning of the nanostructured Cu{sub 2}O films has been studied using XRD, and micro-Raman and photoluminescence spectroscopy.

  16. 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.

  17. Influence of CdTe Deposition Temperature and Window Thickness on CdTe Grain Size and Lifetime After CdCl2 Recrystallization

    Energy Technology Data Exchange (ETDEWEB)

    Amarasinghe, Mahisha; Colegrove, Eric; Moutinho, Helio; Albin, David; Duenow, Joel; Johnston, Steve; Kephart, Jason; Sampath, Walajabad; Al-Jassim, Mowafak; Sivananthan, Siva; Metzger, Wyatt K.

    2018-03-01

    Grain structure influences both transport and recombination in CdTe solar cells. Larger grains generally are obtained with higher deposition temperatures, but commercially it is important to avoid softening soda-lime glass. Furthermore, depositing at lower temperatures can enable different substrates and reduced cost in the future. We examine how initial deposition temperatures and morphology influence grain size and lifetime after CdCl2 recrystallization. Techniques are developed to estimate grain distribution quickly with low-cost optical microscopy, which compares well with electron backscatter diffraction data providing corroborative assessments of exposed CdTe grain structures. Average grain size increases as a function of CdCl2 temperature. For lower temperature close-spaced sublimation CdTe depositions, there can be more stress and grain segregation during recrystallization. However, the resulting lifetimes and grain sizes are similar to high-temperature CdTe depositions. The grain structures and lifetimes are largely independent of the presence and/or interdiffusion of Se at the interface, before and after the CdCl2 treatment.

  18. Influence of manganite powder grain size and Ag-particle coating on the magnetocaloric effect and the active magnetic regenerator performance

    DEFF Research Database (Denmark)

    Turcaud, J.A.; Neves Bez, Henrique; Ruiz-Trejo, E.

    2015-01-01

    be significantly modified by the Ag-particle coating when the material is examined in sintered pellet form and we compare results with a second manganite composition La0.67Ca0.33MnO3 with significantly smaller grain size. However, we find that this microstructural engineering does not improve the performance...... of the active magnetic regenerator cycle using the silver decorated material in powder form. The regenerator performance is improved by the reduction of the powder grain size of the refrigerant which we attribute to improved thermal management due to increased surface to volume ratio. © 2015 Acta Materialia Inc......The magnetocaloric performance of La0.67Ca0.27Sr0.06Mn1.05O3 is investigated as a function of the powder grain size and also as a function of decoration of grains with highly conductive silver particulates as a coating layer. We demonstrate that the thermal and electrical conductivities can...

  19. Effect of grain size on amplitude-dependent internal friction in polycrystalline copper. Do takessho no naibu masatsu no shinpuku izon sei ni oyobosu kessho ryukei no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Goto, H.; Nishino, Y.; Asano, S. (Nagoya Inst. of Technology, Nagoya (Japan))

    1991-08-20

    In this research, amplitude-dependency of internal friction was measured on various polycrystalline copper of varying grain size. Furthermore, the measurement data of amplitude-dependency of internal friction were analyzed from the phenomenological standpoint and microplastic strain was calculated as a function of stress. The obtained correlation between microplastic strain and stress corresponded to the stress-strain curve obtainable from normal tensile tests. Hence, comparing with the Hall-Petch relation, the relationship between flow stress and grain size in the microplastiic zone was discussed. The obtained results are summarized as follows: When grains were refined, amplitude dependency of internal friction was inhibited. As a result of the analysis of the data obtained, it was found that the flow stress in the microplastic zone increased following refining of grains. This agreed qualitatively with the macro deformation obtained from normal tensile tests. The grain size dependency of flow stress in the microplastic zone did not follow the normal Hall-Pitch relation, but the plastic strain increased, the dependency moved towards it. 16 refs., 4 figs.

  20. Effects of grain size and humidity on fretting wear in fine-grained alumina, Al{sub 2}O{sub 3}/TiC, and zirconia

    Energy Technology Data Exchange (ETDEWEB)

    Krell, A. [Fraunhofer Inst. for Ceramic Technologies and Sintered Materials, Dresden (Germany); Klaffke, D. [Federal Inst. for Materials Research and Testing, Berlin (Germany)

    1996-05-01

    Friction and wear of sintered alumina with grain sizes between 0.4 and 3 {micro}m were measured in comparison with Al{sub 2}O{sub 3}/TiC composites and with tetragonal ZrO{sub 2} (3 mol% Y{sub 2}O{sub 3}). The dependence on the grain boundary toughness and residual microstresses is investigated, and a hierarchical order of influencing parameters is observed. In air, reduced alumina grain sizes improve the micromechanical stability of the grain boundaries and the hardness, and reduced wear is governed by microplastic deformation, with few pullout events. Humidity and water slightly reduce the friction of all of the investigated ceramics. In water, this effect reduces the wear of coarser alumina microstructures. The wear of aluminas and of the Al{sub 2}O{sub 3}/TiC composite is similar; it is lower than observed in zirconia, where extended surface cracking occurs at grain sizes as small as 0.3 {micro}m.

  1. Improvement of the mechanical properties of spark plasma sintered hap bioceramics by decreasing the grain size and by adding multi-walled carbon nanotubes

    Directory of Open Access Journals (Sweden)

    Veljović Đ.

    2013-01-01

    Full Text Available Composites based on HAP and oxidized multi-walled carbon nanotubes (o-MWCNT and monophase HAP materials were processed by spark plasma sintering. Starting from stoichiometric nano-sized HAP powder, monophase bioceramics were obtained with a density close to the theoretical one and with an average grain size of several hundred nanometers to micron dimensions. It was shown that decreasing the sintering temperature resulted in a decrease of the grain size, which affected an increase in the fracture toughness and hardness. The fracture toughness of an HAP/ o-MWCNT bioceramic processed at 900°C for only 5 min was 30 % higher than that of monophase HAP materials obtained under the same conditions. The addition of MWCNT during SPS processing of HAP materials caused a decrease in the grain size to the nano-dimension, which was one of the reasons for the improved mechanical properties. [Projekat Ministarstva nauke Republike Srbije, br. III45019 i FP7-REGPOT-2009-1 NANOTECH FTM, Grant Agreement Number: 245916

  2. Effect of the grain size of the soil on the measured activity and variation in activity in surface and subsurface soil samples

    International Nuclear Information System (INIS)

    Sulaiti, H.A.; Rega, P.H.; Bradley, D.; Dahan, N.A.; Mugren, K.A.; Dosari, M.A.

    2014-01-01

    Correlation between grain size and activity concentrations of soils and concentrations of various radionuclides in surface and subsurface soils has been measured for samples taken in the State of Qatar by gamma-spectroscopy using a high purity germanium detector. From the obtained gamma-ray spectra, the activity concentrations of the 238U (226Ra) and /sup 232/ Th (/sup 228/ Ac) natural decay series, the long-lived naturally occurring radionuclide 40 K and the fission product radionuclide 137CS have been determined. Gamma dose rate, radium equivalent, radiation hazard index and annual effective dose rates have also been estimated from these data. In order to observe the effect of grain size on the radioactivity of soil, three grain sizes were used i.e., smaller than 0.5 mm; smaller than 1 mm and greater than 0.5 mm; and smaller than 2 mm and greater than 1 mm. The weighted activity concentrations of the 238U series nuclides in 0.5-2 mm grain size of sample numbers was found to vary from 2.5:f:0.2 to 28.5+-0.5 Bq/kg, whereas, the weighted activity concentration of 4 degree K varied from 21+-4 to 188+-10 Bq/kg. The weighted activity concentrations of 238U series and 4 degree K have been found to be higher in the finest grain size. However, for the 232Th series, the activity concentrations in the 1-2 mm grain size of one sample were found to be higher than in the 0.5-1 mm grain size. In the study of surface and subsurface soil samples, the activity concentration levels of 238 U series have been found to range from 15.9+-0.3 to 24.1+-0.9 Bq/kg, in the surface soil samples (0-5 cm) and 14.5+-0.3 to 23.6+-0.5 Bq/kg in the subsurface soil samples (5-25 cm). The activity concentrations of 232Th series have been found to lie in the range 5.7+-0.2 to 13.7+-0.5 Bq/kg, in the surface soil samples (0-5 cm)and 4.1+-0.2 to 15.6+-0.3 Bq/kg in the subsurface soil samples (5-25 cm). The activity concentrations of 4 degree K were in the range 150+-8 to 290+-17 Bq/kg, in the surface

  3. Gas-Grain Chemical Models: Inclusion of a Grain Size Distribution and a Study Of Young Stellar Objects in the Magellanic Clouds

    Science.gov (United States)

    Pauly, Tyler Andrew

    2017-06-01

    Computational models of interstellar gas-grain chemistry have aided in our understanding of star-forming regions. Chemical kinetics models rely on a network of chemical reactions and a set of physical conditions in which atomic and molecular species are allowed to form and react. We replace the canonical single grain-size in our chemical model MAGICKAL with a grain size distribution and analyze the effects on the chemical composition of the gas and grain surface in quiescent and collapsing dark cloud models. We find that a grain size distribution coupled with a temperature distribution across grain sizes can significantly affect the bulk ice composition when dust temperatures fall near critical values related to the surface binding energies of common interstellar chemical species. We then apply the updated model to a study of ice formation in the cold envelopes surrounding massive young stellar objects in the Magellanic Clouds. The Magellanic Clouds are local satellite galaxies of the Milky Way, and they provide nearby environments to study star formation at low metallicity. We expand the model calculation of dust temperature to include a treatment for increased interstellar radiation field intensity; we vary the radiation field to model the elevated dust temperatures observed in the Magellanic Clouds. We also adjust the initial elemental abundances used in the model, guided by observations of Magellanic Cloud HII regions. We are able to reproduce the relative ice fractions observed, indicating that metal depletion and elevated grain temperature are important drivers of the envelope ice composition. The observed shortfall in CO in Small Magellanic Cloud sources can be explained by a combination of reduced carbon abundance and increased grain temperatures. The models indicate that a large variation in radiation field strength is required to match the range of observed LMC abundances. CH 3OH abundance is found to be enhanced (relative to total carbon abundance) in

  4. 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...

  5. Lithological, grain-size and architectural trends in the holocene Rhine-Meuse delta-insights from 3D voxel models

    NARCIS (Netherlands)

    Stafleu, J.; Busschers, F.S.

    2014-01-01

    TNO Geological Survey of the Netherlands systematically produces 3D voxel models for answering subsurface related questions. The unique combination of vast amounts of borehole data and the voxelbased approach makes the models valuable new sources for exploring the Quaternary fluvial record. The

  6. 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.

  7. X-ray imaging resolution of phosphor screens prepared with different grains size and shape of granular Lu2O3:Eu

    Science.gov (United States)

    Seferis, I. E.; Michail, C.; Zeler, J.; Valais, I.; Fountos, G.; Kalyvas, N.; Bakas, A.; Kandarakis, I.; Zych, E.; Panayiotakis, G. S.

    2017-11-01

    The influence of the grain shape and size on spatial resolution (ranging from nano to micro scale) of various Lu2O3:Eu phosphor screens was investigated. All screens were prepared using the sedimentation method. Three screens were prepared with spherical grains and sizes 50 nm, 200 nm and 5 μm, whilst two screens with rod-like shape grains and sizes 500 nm and 1-8 μm. All screens were coupled to a high resolution CMOS digital imaging sensor (Remote RadEye HR) consisting of 1200 x 1600 pixels with 22.5 μm pixel pitch. Experiments were performed under radiographic conditions, using 70 kVp tube voltage and 63 mAs tube load. Spatial resolution was assessed utilizing the Modulation Transfer Function (MTF). It was found that the influence of the grains shape on imaging performance was more crucial than the grain size. The rod-like grains showed very poor spatial resolution. The influence of grains size between 50 nm 200 nm and 5 μm was negligible on MTF values.

  8. Effects by the microstructure after hot and cold rolling on the texture and grain size after final annealing of ferritic non-oriented FeSi electrical steel

    Science.gov (United States)

    Schneider, J.; Stöcker, A.; Franke, A.; Kawalla, R.

    2018-04-01

    The magnetic properties of fully processed non-oriented FeSi electrical steel are characterized by their magnetization behavior and specific magnetic losses. The magnetic properties are determined by the texture and microstructure. Less gamma fiber intensity and a high intensity of preferable texture components, especially cube fiber texture, are desirable to obtain an excellent magnetizing behavior. Furthermore, large grain sizes are necessary to reach low values of the specific magnetic losses. The fabrication route of the fully processed non-oriented electrical steels comprises a heavy cold rolling of the hot rolled material before final annealing. To fulfill the requirements on large grain size for low loss materials, grain growth, which appears after complete recrystallization, plays an important role. In this paper we will analyze the influence of different microstructures of the hot strip and the resulting microstructure after cold rolling on the appearance of recrystallization and grain growth after final annealing. The evolution of texture reflects the present ongoing softening processes: recovery, recrystallization and finally grain growth at the given annealing conditions. It will be shown that the image of texture at recrystallization is remarkable different from the texture at grain growth. Substantially grain growth is obtained at lower annealing temperatures for an optimum microstructure of the hot rolled material.

  9. 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.

  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

    2015-11-12

    Planning for use of a dune field aquifer for managed aquifer recharge (MAR) requires that hydraulic properties need to be estimated over a large geographic area. Saturated hydraulic conductivity of dune sands is commonly estimated from grain size distribution data by employing some type of empirical equation. Over 50 samples from the Wadi Khulays dune field in Western Saudi Arabia were collected and the grain size distribution, porosity, and hydraulic conductivity were measured. An evaluation of 20 existing empirical equations showed a generally high degree of error in the predicted compared to the measured hydraulic conductivity values of these samples. Statistical analyses comparing estimated versus measured hydraulic conductivity demonstrated that there is a significant relationship between hydraulic conductivity and mud percentage (and skewness). The modified Beyer equation, which showed a generally low prediction error, was modified by adding a second term fitting parameter related to the mud concentration based on 25 of the 50 samples analyzed. An inverse optimization process was conducted to quantify the fitting parameter and a new empirical equation was developed. This equation was tested against the remaining 25 samples analyzed and produced an estimated saturated hydraulic conductivity with the lowest error of any empirical equation. This methodology can be used for large dune field hydraulic conductivity estimation and reduce planning costs for MAR systems.

  11. Grain size and nanoscale effects on the nonlinear pull-in instability and vibrations of electrostatic actuators made of nanocrystalline material

    Science.gov (United States)

    Gholami, R.; Ansari, R.

    2018-01-01

    Presented herein is the study of grain size, grain surface energy and small scale effects on the nonlinear pull-in instability and free vibration of electrostatic nanoscale actuators made of nanocrystalline silicon (Nc-Si). A Mori-Tanaka micromechanical model is utilized to calculate the effective material properties of Nc-Si considering material structure inhomogeneity, grain size and grain surface energy. The small-scale effect is also taken into account using Mindlin’s strain gradient theory. Governing equations are derived in the discretized weak form using the variational differential quadrature method based on the third-order shear defamation beam theory in conjunction with the von Kármán hypothesis. The electrostatic actuation is modeled considering the fringing field effects based upon the parallel plate approximation. Moreover, the Casimir force effect is considered. The pseudo arc-length continuation technique is used to obtain the applied voltage-deflection curve of Nc-Si actuators. Then, a time-dependent small disturbance around the deflected configuration is assumed to solve the free vibration problem. By performing a numerical study, the influences of various factors such as length scale parameter, volume fraction of the inclusion phase, density ratio, average inclusion radius and Casimir force on the pull-in instability and free vibration of Nc-Si actuators are investigated.

  12. Temperature and grain size effect on the fatigue and creep-fatigue behavior of OFHC copper and CuCrZr for fusion application

    International Nuclear Information System (INIS)

    Pan, X.; Wu, X.; Stubbins, J.

    2007-01-01

    Full text of publication follows: Copper and its alloys are prime candidates for high heat flux applications in fusion reactor systems due to their high thermal conductivity. This class of materials is of particular interest for the first wall and divertor structures in ITER. In service, these components will endure not only the cyclic loading but also the stress relaxation and microstructural recovery during the pulsed mode operation. Thus the fatigue and creep-fatigue behavior is central to materials selection since thermal-mechanical cycling will limit component life. Several studies of the fatigue performance which include hold time effects indicate that the hold process can substantially degrade the material fatigue life even at room temperature, 0.22 T m , which is well below temperatures typically associated with thermally-induced creep and stress relaxation. This reduction in fatigue life is found to be most dramatic in the low strain amplitude, high cycle fatigue regime where fatigue lives can be reduced by a factor of more than two. It is also found that the reduction in fatigue life requires only a short hold period of 10 s, much shorter than the anticipated on/off cycles in ITER of 1000 s/100 s. Grain size is an important parameter affecting material fatigue performance. Early studies show that fatigue life of copper reduces with increasing the grain size in both continuous fatigue and creep-fatigue conditions at room temperature. It is found that the mode of fatigue crack initiation changes with changing of the testing modes, grain size and strain amplitudes, which finally determines the fatigue life of OFHC copper. The mechanisms controlling the room temperature creep damage in OHFC copper with different grain size are interesting and should also be investigated at higher temperatures. To examine this issue in greater detail, a series of will be conducted with different grain sizes at different temperature. Selected interrupted fatigue and creep

  13. 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

    The presently active Yellow River (Huanghe) delta lobe has been formed since 1976 when the river was artificially diverted. The process and driving forces of morphological evolution of the present delta lobe still remain unclear. Here we examined the stepwise morphological evolution of the active Yellow River delta lobe including both the subaerial and the subaqueous components, and illustrated the critical roles of riverine discharge and sediment grain size in dominating the deltaic evolution. The critical sediment loads for maintaining the delta stability were also calculated from water discharge and sediment load measured at station Lijin, the last gauging station approximately 100 km upstream from the river mouth. The results indicated that the development of active delta lobe including both subaerial and subaqueous components has experienced four sequential stages. During the first stage (1976-1981) after the channel migration, the unchannelized river flow enhanced deposition within the channel and floodplain between Lijin station and the river mouth. Therefore, the critical sediment supply calculated by the river inputs obtained from station Lijin was the highest. However, the actual sediment load at this stage (0.84 Gt/yr) was more than twice of the critical sediment load ( 0.35 Gt/yr) for sustaining the active subaerial area, which favored a rapid seaward progradation of the Yellow River subaerial delta. During the second stage (1981-1996), the engineering-facilitated channelized river flow and the increase in median grain size of suspended sediment delivered to the sea resulted in the critical sediment load for keeping the delta stability deceasing to 0.29 Gt/yr. The active delta lobe still gradually prograded seaward at an accretion rate of 11.9 km2/yr at this stage as the annual sediment load at Lijin station was 0.55 Gt/yr. From 1996 to 2002, the critical sediment load further decreased to 0.15 Gt/yr with the sediment grain size increased to 22.5

  14. Terrestrial in situ sampling of dust devils (relative particle loads and vertical grain size distributions) as an equivalent for martian dust devils.

    Science.gov (United States)

    Raack, J.; Dennis, R.; Balme, M. R.; Taj-Eddine, K.; Ori, G. G.

    2017-12-01

    Dust devils are small vertical convective vortices which occur on Earth and Mars [1] but their internal structure is almost unknown. Here we report on in situ samples of two active dust devils in the Sahara Desert in southern Morocco [2]. For the sampling we used a 4 m high aluminium pipe with sampling areas made of removable adhesive tape. We took samples between 0.1-4 m with a sampling interval of 0.5 m and between 0.5-2 m with an interval of 0.25 m, respectively. The maximum diameter of all particles of the different sampling heights were then measured using an optical microscope to gain vertical grain size distributions and relative particle loads. Our measurements imply that both dust devils have a general comparable internal structure despite their different strengths and dimensions which indicates that the dust devils probably represents the surficial grain size distribution they move over. The particle sizes within the dust devils decrease nearly exponential with height which is comparable to results by [3]. Furthermore, our results show that about 80-90 % of the total particle load were lifted only within the first meter, which is a direct evidence for the existence of a sand skirt. If we assume that grains with a diameter dust coverage is larger [5], although the atmosphere can only suspend smaller grain sizes ( dust devils each day which were up to several hundred meters tall and had diameters of several tens of meters. This implies a much higher input of fine grained material into the atmosphere (which will have an influence on the climate, weather, and human health [7]) compared to the relative small dust devils sampled during our field campaign. [1] Thomas and Gierasch (1985) Science 230 [2] Raack et al. (2017) Astrobiology [3] Oke et al. (2007) J. Arid Environ. 71 [4] Balme and Greeley (2006) Rev. Geophys. 44 [5] Christensen (1986) JGR 91 [6] Newman et al. (2002) JGR 107 [7] Gillette and Sinclair (1990) Atmos. Environ. 24

  15. The Importance of Physical Models for Deriving Dust Masses and Grain Size Distributions in Supernova Ejecta. I. Radiatively Heated Dust in the Crab Nebula

    Science.gov (United States)

    Temim, Tea; Dwek, Eli

    2013-01-01

    Recent far-infrared (IR) observations of supernova remnants (SNRs) have revealed significantly large amounts of newly condensed dust in their ejecta, comparable to the total mass of available refractory elements. The dust masses derived from these observations assume that all the grains of a given species radiate at the same temperature, regardless of the dust heating mechanism or grain radius. In this paper, we derive the dust mass in the ejecta of the Crab Nebula, using a physical model for the heating and radiation from the dust. We adopt a power-law distribution of grain sizes and two different dust compositions (silicates and amorphous carbon), and calculate the heating rate of each dust grain by the radiation from the pulsar wind nebula. We find that the grains attain a continuous range of temperatures, depending on their size and composition. The total mass derived from the best-fit models to the observed IR spectrum is 0.019-0.13 Solar Mass, depending on the assumed grain composition. We find that the power-law size distribution of dust grains is characterized by a power-law index of 3.5-4.0 and a maximum grain size larger than 0.1 micron. The grain sizes and composition are consistent with what is expected for dust grains formed in a Type IIP supernova (SN). Our derived dust mass is at least a factor of two less than the mass reported in previous studies of the Crab Nebula that assumed more simplified two-temperature models. These models also require a larger mass of refractory elements to be locked up in dust than was likely available in the ejecta. The results of this study show that a physical model resulting in a realistic distribution of dust temperatures can constrain the dust properties and affect the derived dust masses. Our study may also have important implications for deriving grain properties and mass estimates in other SNRs and for the ultimate question of whether SNe are major sources of dust in the Galactic interstellar medium and in

  16. Effects of grain size, mineralogy, and acid-extractable grain coatings on the distribution of the fallout radionuclides 7Be, 10Be, 137Cs, and 210Pb in river sediment

    Science.gov (United States)

    Singleton, Adrian A.; Schmidt, Amanda H.; Bierman, Paul R.; Rood, Dylan H.; Neilson, Thomas B.; Greene, Emily Sophie; Bower, Jennifer A.; Perdrial, Nicolas

    2017-01-01

    Grain-size dependencies in fallout radionuclide activity have been attributed to either increase in specific surface area in finer grain sizes or differing mineralogical abundances in different grain sizes. Here, we consider a third possibility, that the concentration and composition of grain coatings, where fallout radionuclides reside, controls their activity in fluvial sediment. We evaluated these three possible explanations in two experiments: (1) we examined the effect of sediment grain size, mineralogy, and composition of the acid-extractable materials on the distribution of 7Be, 10Be, 137Cs, and unsupported 210Pb in detrital sediment samples collected from rivers in China and the United States, and (2) we periodically monitored 7Be, 137Cs, and 210Pb retention in samples of known composition exposed to natural fallout in Ohio, USA for 294 days. Acid-extractable materials (made up predominately of Fe, Mn, Al, and Ca from secondary minerals and grain coatings produced during pedogenesis) are positively related to the abundance of fallout radionuclides in our sediment samples. Grain-size dependency of fallout radionuclide concentrations was significant in detrital sediment samples, but not in samples exposed to fallout under controlled conditions. Mineralogy had a large effect on 7Be and 210Pb retention in samples exposed to fallout, suggesting that sieving sediments to a single grain size or using specific surface area-based correction terms may not completely control for preferential distribution of these nuclides. We conclude that time-dependent geochemical, pedogenic, and sedimentary processes together result in the observed differences in nuclide distribution between different grain sizes and substrate compositions. These findings likely explain variability of measured nuclide activities in river networks that exceeds the variability introduced by analytical techniques as well as spatial and temporal differences in erosion rates and processes. In short, we

  17. Efficiency enhancement of ZnO/Cu2O solar cells with well oriented and micrometer grain sized Cu2O films

    Science.gov (United States)

    Zang, Zhigang

    2018-01-01

    Cu2O is one of the attractive photovoltaic materials for solar cells because of its low cost, nontoxicity, and good mobility. In this paper, an obvious enhancement of power conversion efficiency (PCE) for ZnO/Cu2O solar cells with perfectly oriented and micrometer grain sized Cu2O films was experimentally demonstrated. Cu2O was fabricated using radical oxidation of Cu foils at a low temperature of 500 °C. When followed by a rapid quenching and post annealing treatment, the perfectly oriented and micrometer sized Cu2O crystals (3˜4 μm) could be obtained. The crystal structure and optical properties of Cu2O were investigated in detail. Compared to conventional solar cells without any treatment, the PCE of the solar cells based on Cu2O with treatment was 3.18%, corresponding to a significant PCE improvement of 60.6%.

  18. Suspended Matter, Chl-a, CDOM, Grain Sizes, and Optical Properties in the Arctic Fjord-Type Estuary, Kangerlussuaq, West Greenland During Summer

    DEFF Research Database (Denmark)

    Lund-Hansen, L. C.; Andersen, T. J.; Nielsen, Morten Holtegaard

    2010-01-01

    Optical constituents as suspended particulate matter (SPM), chlorophyll (Chl-a), colored dissolved organic matter (CDOM), and grain sizes were obtained on a transect in the arctic fjord-type estuary Kangerlussuaq (66A degrees) in August 2007 along with optical properties. These comprised diffuse...... water outlet. Values of optical constituents and properties decreased with distance from the melt water outlet to a more or less constant level in central and outer part of the estuary. There was a strong correlation between inorganic suspended matter (SPMI) and diffuse attenuation coefficient K (d...... from the very high turbid melt water outlet to clear marine waters. Results showed a strong spatial variation with high values as for suspended matter concentrations, CDOM, diffuse attenuation coefficient K (d)(PAR), particle beam attenuation coefficients (c (p)), and reflectance R(-0, PAR) at the melt...

  19. The grain size dependency of vesicular particle shapes strongly affects the drag of particles. First results from microtomography investigations of Campi Flegrei fallout deposits

    Science.gov (United States)

    Mele, Daniela; Dioguardi, Fabio

    2018-03-01

    Acknowledging the grain size dependency of shape is important in volcanology, in particular when dealing with tephra produced and emplaced during and after explosive volcanic eruptions. A systematic measurement of the tridimensional shape of vesicular pyroclasts of Campi Flegrei fallout deposits (Agnano-Monte Spina, Astroni 6 and Averno 2 eruptions) varying in size from 8.00 to 0.016 mm has been carried out by means of X-Ray Microtomography. Data show that particle shape changes with size, especially for juvenile vesicular clasts, since it is dependent on the distribution and size of vesicles that contour the external clast outline. Two drag laws that include sphericity in the formula were used for estimating the dependency of settling velocity on shape. Results demonstrate that it is not appropriate to assume a size-independent shape for vesicular particles, in contrast with the approach commonly employed when simulating the ash dispersion in the atmosphere.

  20. Grain-Size Control on the Rare Earth Elements Distribution in the Late Diagenesis of Cretaceous Shales from the Southern Apennines (Italy

    Directory of Open Access Journals (Sweden)

    Francesco Cavalcante

    2014-01-01

    Full Text Available Different grain-size fractions of samples collected from shales were investigated to determine the role of late diagenetic grade and mineralogy on the rare earth elements (REE distribution. The samples were collected from Upper Cretaceous varicoloured shales of the Sicilide Unit near the Corleto Perticara villages, Southern Apennines (Italy. The mineralogical and chemical composition of the sample’s five fractions (>63, 32–63, 2–32, 0.1–2, and <0.1 µm was studied. The data indicate that certain accessory minerals are more important than clay minerals in controlling the REE distribution. In particular, zircon controls the distribution of earth elements in the 0.1–2 µm fraction and is an efficient mechanism in determining the concentration and distribution of REEs in the studied shales.

  1. Local hysteresis and grain size effect in Pb(Mg1/3Nb2/3)O3- PbTiO3 thin films

    Science.gov (United States)

    Shvartsman, V. V.; Emelyanov, A. Yu.; Kholkin, A. L.; Safari, A.

    2002-07-01

    The local piezoelectric properties of relaxor ferroelectric films of solid solutions 0.9Pb(Mg1/3Nb2/3)O3- 0.1PbTiO3 were investigated by scanning force microscopy (SFM) in a piezoelectric contact mode. The piezoelectric hysteresis loops were acquired in the interior of grains of different sizes. A clear correlation between the values of the effective piezoelectric coefficients, deff, and the size of the respective grains is observed. Small grains exhibit slim piezoelectric hysteresis loops with low remanent deff, whereas relatively strong piezoelectric activity is characteristic of larger grains. Part of the grains (approx20-25%) is strongly polarized without application of a dc field. The nature of both phenomena is discussed in terms of the internal bias field and grain size effects on the dynamics of nanopolar clusters.

  2. The effect of Fe, Mn, Ni and Pb Load on Soil and its enrichment factor ratios in different soil grain size fractions as an Indicator for soil pollution

    International Nuclear Information System (INIS)

    Rabie, F.H.; Abdel-Sabour, M.F.

    2000-01-01

    An industrial area north of greater Cairo was selected to investigate the impact of intensive industrial activities on soil characteristics and Fe, Mn, Ni and Pb total content. The studied area was divided to six sectors according to its source of irrigation water and/or probability of pollution. Sixteen soil profiles were dug and soil samples were taken, air dried, fractionated to different grain size fractions, then total heavy metals (Fe, Mn, Ni and Pb) were determined using ICP technique. The enrichment factor for each metal for each soil fraction/soil layer was estimated and discussed. The highest EF ratios in the clay fraction was mainly with Pb which indicated the industrial impact on the soil. In case of sand fraction, Mn was the highest always compared to other studied metals. Concerning silt fraction, a varied accumulation of Fe, Mn, and Pb was observed with soil depth and different soil profiles

  3. 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.

  4. Brittle grain-size reduction of feldspar, phase mixing and strain localization in granitoids at mid-crustal conditions (Pernambuco shear zone, NE Brazil)

    Science.gov (United States)

    Viegas, Gustavo; Menegon, Luca; Archanjo, Carlos

    2016-03-01

    The Pernambuco shear zone (northeastern Brazil) is a large-scale strike-slip fault that, in its eastern segment, deforms granitoids at mid-crustal conditions. Initially coarse-grained (> 50 µm) feldspar porphyroclasts are intensively fractured and reduced to an ultrafine-grained mixture consisting of plagioclase and K-feldspar grains ( and rhomb slip systems. However, the grain size in monophase recrystallized domains decreases when moving from the quartz monomineralic veins to the thin ribbons embedded in the feldspathic C' bands (14 µm vs. 5 µm respectively). The fine-grained feldspar mixture has a weak crystallographic-preferred orientation interpreted as the result of shear zone parallel-oriented growth during diffusion creep, as well as the same composition as the fractured porphyroclasts, suggesting that it generated by mechanical fragmentation of rigid porphyroclasts with a negligible role of chemical disequilibrium. Once C' shear bands were generated and underwent viscous deformation at constant stress conditions, the polyphase feldspathic aggregate would have deformed at a strain rate 1 order of magnitude faster than the monophase quartz monomineralic veins, as evidenced by applying experimentally and theoretically calibrated flow laws for dislocation creep in quartz and diffusion creep in feldspar. Overall, our data set indicates that feldspar underwent a brittle-viscous transition while quartz was deforming via crystal plasticity. The resulting rock microstructure consists of a two-phase rheological mixture (fine-grained feldspars and recrystallized quartz) in which the polyphase feldspathic material localized much of the strain. Extensive grain-size reduction and weakening of feldspars is attained in the East Pernambuco mylonites mainly via fracturing which would trigger a switch to diffusion creep and strain localization without a prominent role of metamorphic reactions.

  5. Brittle grain size reduction of feldspar, phase mixing and strain localization in granitoids at mid-crustal conditions (Pernambuco shear zone, NE Brazil)

    Science.gov (United States)

    Viegas, Gustavo; Menegon, Luca; Archanjo, Carlos

    2016-04-01

    The Pernambuco shear zone (northeastern Brazil) is a large-scale strike-slip fault that, in its eastern segment, deforms granitoids at mid-crustal conditions. Initially coarse (> 50 μm) grained feldspar porphyroclasts are intensively fractured and reduced to an ultrafine-grained mixture consisting of plagioclase and K-feldspar grains ( and rhomb slip systems. However, the grain size in monophase recrystallized domains decreases when moving from the monomineralic veins to the thin ribbons embedded in the feldspathic C' bands (14 μm vs 5 μm, respectively).The fine-grained feldspar mixture has a weak crystallographic preferred orientation interpreted as the result of oriented growth during diffusion creep, as well as the same composition as the fractured porphyroclasts, suggesting that it generated by mechanical fragmentation of rigid porphyroclasts with a negligible role of chemical disequilibrium. Assuming that the C' shear bands deformed under constant stress conditions, the polyphase feldspathic aggregate would have deformed at a strain rate one order of magnitude faster than the monophase quartz ribbons. Overall, our dataset indicates that feldspar underwent a brittle-viscous transition while quartz was deforming via crystalline plasticity. The resulting rock microstructure consists of a two-phase rheological mixture (fine-grained feldspars and recrystallized quartz) in which the feldspathic material localized much of the strain. Extensive grain-size reduction and weakening of feldspars is attained in the East Pernambuco shear zone mainly via fracturing under relatively fluid-absent conditions which would trigger a switch to diffusion creep and further strain localization without a prominent role of metamorphic reactions.

  6. A Method to Increase Current Density in a Mono Element Internal Tin Processed Superconductor Utilizing Zr Oxide to Refine Grain Size

    Energy Technology Data Exchange (ETDEWEB)

    Bruce A. Zeitlin, Eric Gregory

    2008-04-07

    The effect of Oxygen on (Nb1Zr)3Sn multifilament conductors manufactured by the Mono Element Internal Tin (MEIT) process was explored to improve the current density by refining the grain size. This followed work first done by General Electric on the Nb3Sn tape process. Techniques to fabricate the more difficult Nb1Zr composites are described and allowed fabrication of long lengths of .254 mm diameter wire from an 88.9 mm diameter billet. Oxygen was incorporated through the use of SnO2 mixed with tin powder and incorporated into the core. These were compared to samples with Ti+Sn and Cu+Sn cores. Heat treatments covered the range of 700 C to 1000 C. Current density vs. H, grain size, and reaction percentages are provided for the materials tested. The Oxygen gave superior results in the temperature range of 815-1000 C. It also stabilized the filament geometry of the array in comparison to the other additions at the higher temperatures. At 815 C a peak in layer Jc yielded values of 2537 A/mm2 at 12 T and 1353 A/mm2 at 15T, 8-22% and 30-73% greater respectively than 700 C values. Results with Oxygen at high temperature show the possibility of high speed continuous reaction of the composite versus the current batch or react in place methods. In general the Ti additions gave superior results at the lower reaction temperature. Future work is suggested to determine if the 815 C reaction temperature can lead to higher current density in high tin (Nb1Zr+Ox)3Sn conductors. A second technique incorporated oxygen directly into the Nb1Zr rods through heat treatment with Nb2O5 at 1100 C for 100 hours in vacuum prior to extrusion. The majority of the filaments reduced properly in the composite but some local variations in hardness led to breakage at smaller diameters.

  7. 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.

  8. Unit-bar migration and bar-trough deposition: impacts on hydraulic conductivity and grain size heterogeneity in a sandy streambed

    Science.gov (United States)

    Korus, Jesse T.; Gilmore, Troy E.; Waszgis, Michele M.; Mittelstet, Aaron R.

    2017-09-01

    The hydrologic function of riverbeds is greatly dependent upon the spatiotemporal distribution of hydraulic conductivity and grain size. Vertical hydraulic conductivity (K v) is highly variable in space and time, and controls the rate of stream-aquifer interaction. Links between sedimentary processes, deposits, and K v heterogeneity have not been well established from field studies. Unit bars are building blocks of fluvial deposits and are key to understanding controls on heterogeneity. This study links unit bar migration to K v and grain size variability in a sand-dominated, low-sinuosity stream in Nebraska (USA) during a single 10-day hydrologic event. An incipient bar formed parallel to the thalweg and was highly permeable and homogenous. During high flow, this bar was submerged under 10-20 cm of water and migrated 100 m downstream and toward the channel margin, where it became markedly heterogeneous. Low-K v zones formed in the subsequent heterogeneous bar downstream of the original 15-40-cm-thick bar front and past abandoned bridge pilings. These low-K v zones correspond to a discontinuous 1-cm layer of fine sand and silt deposited in the bar trough. Findings show that K v heterogeneity relates chiefly to the deposition of suspended materials in low-velocity zones downstream of the bar and obstructions, and to their subsequent burial by migration of the bar during high flow. Deposition of the unit bar itself, although it emplaced the vast majority of the sediment volume, was secondary to bar-trough deposition as a control on the overall pattern of heterogeneity.

  9. Elemental and Sr–Nd isotopic compositional disparity of riverine sediments around the Yellow Sea: Constraints from grain-size and chemical partitioning

    International Nuclear Information System (INIS)

    Lim, Dhongil; Jung, Hoisoo; Xu, Zhaokai; Jeong, Kapsik; Li, Tiegang

    2015-01-01

    To obtain a better understanding of the source compositions of the river sediments around the Yellow Sea and their relationship with source rocks, elements and strontium-neodymium (Sr–Nd) isotopes of different grain-sizes (silt and clay populations) and chemical (labile and residual phases) fractionations in riverine sediments were studied extensively. These results clearly revealed a systematic compositional disparity between Korean river (KR) and Chinese river (CR) sediments, especially in the residual (detrital) fraction. The geochemical dissimilarity between these might reflect inherited signatures of their source rocks but with minor control from chemical weathering. In particular, the remarkable enrichment of some elements (iron (Fe) and magnesium (Mg)) and the behavior of large ion lithophile elements (e.g., barium (Ba), potassium (K) and Sr) during weathering as well as less-radiogenic Sr isotopic compositions implies that CR sediments might be weathering products of relatively more mafic rocks, with abundant ferromagnesian and plagioclase feldspar minerals, compared with KR sediments derived from silicic granites with relatively higher quartz and potassium feldspar contents. This different petrological rationale is clearly evident in an A–CN–K diagram, which estimated the source rock of CR sediments as granodioritic, a composition that reflects accurately the average composition of weathered continental crust in China. The recognition of such geochemical systematics in two river sediments, especially in grain-size and chemically partitioned data, may contribute to the establishment of provenance tracers for the Yellow Sea and East China Sea sediments with multi-sources as well the dust deposition in the western Pacific. - Highlights: • We solved the compositional linkage between river sediments and their source rocks. • Sediments were physically and chemically partitioned for element and Sr–Nd compositions. • Data revealed CR and KR sediments

  10. How Can Polarization States of Reflected Light from Snow Surfaces Inform Us on Surface Normals and Ultimately Snow Grain Size Measurements?

    Science.gov (United States)

    Schneider, A. M.; Flanner, M.; Yang, P.; Yi, B.; Huang, X.; Feldman, D.

    2016-12-01

    The Snow Grain Size and Pollution (SGSP) algorithm is a method applied to Moderate Resolution Imaging Spectroradiometer data to estimate snow grain size from space-borne measurements. Previous studies validate and quantify potential sources of error in this method, but because it assumes flat snow surfaces, however, large scale variations in surface normals can cause biases in its estimates due to its dependence on solar and observation zenith angles. To address these variations, we apply the Monte Carlo method for photon transport using data containing the single scattering properties of different ice crystals to calculate polarization states of reflected monochromatic light at 1500nm from modeled snow surfaces. We evaluate the dependence of these polarization states on solar and observation geometry at 1500nm because multiple scattering is generally a mechanism for depolarization and the ice crystals are relatively absorptive at this wavelength. Using 1500nm thus results in a higher number of reflected photons undergoing fewer scattering events, increasing the likelihood of reflected light having higher degrees of polarization. In evaluating the validity of the model, we find agreement with previous studies pertaining to near-infrared spectral directional hemispherical reflectance (i.e. black-sky albedo) and similarities in measured bidirectional reflectance factors, but few studies exist modeling polarization states of reflected light from snow surfaces. Here, we present novel results pertaining to calculated polarization states and compare dependences on solar and observation geometry for different idealized snow surfaces. If these dependencies are consistent across different ice particle shapes and sizes, then these findings could inform the SGSP algorithm by providing useful relationships between measurable physical quantities and solar and observation geometry to better understand variations in snow surface normals from remote sensing observations.

  11. Distributional Inference

    NARCIS (Netherlands)

    Kroese, A.H.; van der Meulen, E.A.; Poortema, Klaas; Schaafsma, W.

    1995-01-01

    The making of statistical inferences in distributional form is conceptionally complicated because the epistemic 'probabilities' assigned are mixtures of fact and fiction. In this respect they are essentially different from 'physical' or 'frequency-theoretic' probabilities. The distributional form is

  12. The influence of cooling conditions on grain size, secondary phase precipitates and mechanical properties of biomedical alloy specimens produced by investment casting.

    Science.gov (United States)

    Kaiser, R; Williamson, K; O'Brien, C; Ramirez-Garcia, S; Browne, D J

    2013-08-01

    The objective of this work was to investigate and evaluate the effect of the cooling environment on the microstructure, secondary phase precipitates and mechanical properties of an as-cast cobalt alloy. The microstructure of castings has a large bearing on the mechanical properties, grain size, porosity and the morphology of carbide precipitates are thought to influence hardness, tensile strength and ductility. It is postulated that a greater understanding of microstructure and secondary phase precipitate response to casting parameters could lead to the optimisation of casting parameters and serve to reduce the requirement of thermo-mechanical treatments currently applied to refine as-cast structures and achieve adequate mechanical properties. Thermal analysis was performed to determine the critical stages of cooling. Ten millimetre diameter cylindrical specimens which could be machined into tension test specimens were cast and cooled under different conditions to impose different cooling rates. Analytical techniques such as optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX), tensile testing and micro-hardness testing were used to study the specimens. Parameters studied include grain size, secondary dendrite arm spacing, secondary phase precipitates, porosity, hardness, ultimate tensile strength, yield strength and elongation. The microstructure of as-cast Co-28Cr-6Mo was found to consist of a dendritic matrix with secondary phases precipitated at grain boundaries and interdendritic zones. These secondary phase precipitates consist of carbides, rich in chromium and molybdenum. The size and area fraction of carbides was found to decrease significantly with increasing cooling rate while the micro-porosity was only marginally affected. The as-cast grains are illustrated for the first time showing a significant difference in size between insulated and naturally cooled specimens. The secondary dendrite arm spacing was

  13. EFFECT OF GRAIN SIZE AND ACTIVATION TIME OF ZEOLITE TO ADSORPTION AND DESORPTION OF NH4OH AND KCL AS MODEL OF FERTILIZER-ZEOLITE MIX

    Directory of Open Access Journals (Sweden)

    Muhammad Prasantio Bimantio

    2017-10-01

    Full Text Available Zeolites can be used as adsorbent, ion exchange, catalyst, or catalyst carrier. Application of fertilizer use in the zeolite also be one of the interesting topic. Zeolites in a mixture of fertilizer can use to control the release of nutrients. The purpose of this research is to study the effect of grain size and time of the activation of zeolite to adsorption and desorption of NH4OH and KCl as modeling of ZA and KCl fertilizer, to obtain the value of adsorption rate constant (ka and desorption rate constant (kd. This research procedure include: the process of adsorption by adding zeolite with various size and time of activation into a sealed beaker glass and let the adsorption process occurs for 24 hours. After 24 hours, the solution was filtered, the zeolite then put in 100 ml of aquadest into a sealed beaker glass and let the desorption process happened for another 24 hours. Three samples with the largest difference solution concentrations looked for the value of the ka and kd. Zeolite configuration with the largest ka is trialed with fertilizer and compared with the value of ka obtained from modeling. The result for NH4OH adsorbate, -50+60 mesh 2 hours configuration zeolite give the largest ka. For KCl adsorbate, -30+40 mesh 4 hours configuration zeolite give the largest ka. The value between modeling and trials with fertilizers are not much different.

  14. 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.

  15. Grain size, morphometry and mineralogy of airborne input in the Canary basin: evidence of iron particle retention in the mixed layer

    Directory of Open Access Journals (Sweden)

    Alfredo Jaramillo-Vélez

    2016-09-01

    Full Text Available Aeolian dust plays an important role in climate and ocean processes. Particularly, Saharan dust deposition is of importance in the Canary Current due to its content of iron minerals, which are fertilizers of the ocean. In this work, dust particles are characterized mainly by granulometry, morphometry and mineralogy, using image processing and scanning northern Mauritania and the Western Sahara. The concentration of terrigenous material was measured in three environments: the atmosphere (300 m above sea level, the mixed layer at 10 m depth, and 150 m depth. Samples were collected before and during the dust events, thus allowing the effect of Saharan dust inputs in the water column to be assessed. The dominant grain size was coarse silt. Dominant minerals were iron oxy-hydroxides, silicates and Ca-Mg carbonates. A relative increase of iron mineral particles (hematite and goethite was detected in the mixed layer, reflecting a higher permanence of iron in the water column despite the greater relative density of these minerals in comparison with the other minerals. This higher iron particle permanence does not appear to be explained by physical processes. The retention of this metal by colloids or microorganisms is suggested to explain its long residence time in the mixed layer.

  16. Comparison of four monolithic zirconia materials with conventional ones: Contrast ratio, grain size, four-point flexural strength and two-body wear.

    Science.gov (United States)

    Stawarczyk, Bogna; Frevert, Kathrin; Ender, Andreas; Roos, Malgorzata; Sener, Beatrice; Wimmer, Timea

    2016-06-01

    To test the mechanical and optical properties of monolithic zirconia in comparison to conventional zirconia. Specimens were prepared from: monolithic zirconia: Zenostar (ZS), DD Bio ZX(2) hochtransluzent (DD), Ceramill Zolid (CZ), InCoris TZI (IC) and a conventional zirconia Ceramill ZI (CZI). Contrast ratio (N=75/n=15) was measured according to ISO 2471:2008. Grain sizes (N=75/n=15) were investigated with scanning electron microscope. Four-point flexural strength (N=225/n=15/zirconia and aging regime) was measured initially, after aging in autoclave or chewing simulator (ISO 13356:2008). Two-body wear of polished and glazed/veneered specimens (N=108/n=12) was analyzed in a chewing simulator using human teeth as antagonists. Data were analyzed using 2-/1-way ANOVA with post-hoc Scheffé, Kruskal-Wallis-H, Mann-Whitney-U, Spearman-Rho, Weibull statistics and linear mixed models (pzirconia showed higher optical, but lower mechanical properties than conventional zirconia. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Influence of Pulse Electrodeposition and Heat Treatment on Microstructure, Tribological, and Corrosion Behavior of Nano-Grain Size Co-W Coatings

    Science.gov (United States)

    Abazari, Somayeh; Rastegari, Saeed; Kheirandish, Shahram

    2017-07-01

    In the present study, Co-W nano-structured alloy coatings are produced on low-carbon steel substrate by means of pulse electrodeposition from a citrate-based bath under different average current densities and duty cycles. The results indicate that the coating deposited under 60% of duty cycle and 1 A/dm2 of average current density exhibit optimum pulse plating conditions with 44.38 wt.% W, 37 nm grain size, and 758 HV microhardness. The effect of heat treatment temperature on microstructure, composition, corrosion behavior, and morphology of amorphous deposited Co-W alloy with 44 wt.% W was investigated. The microhardness of the coating increased to 1052 HV after heat treatment at 600 °C, which is due to the formation of Co3W and CoWO4 phases in the deposit. Furthermore, the coatings heat-treated at 600 °C had lower friction coefficients and better wear resistance under various loads than before heating.

  18. Optimization of Wet or Dry Micro-blasting on PVD Films by Various Al2O3 Grain Sizes for Improving the Coated Tools' Cutting Performance

    Directory of Open Access Journals (Sweden)

    K. -D. Bouzakis

    2011-06-01

    Full Text Available Micro-blasting on PVD coated tools is an effective technology for improving their cutting performance. Through micro-blasting, compressive stresses are induced into the film, thus increasing the coating hardness, but its brittleness too. Simultaneously, abrasion phenomena are activated, which may lead to roughness augmentation, film thickness decrease and substrate revelation. In this way, for a successful process conduct, it is pivotal to adapt, among others, the applied micro-blasting pressure to the employed medium, air or water. The paper deals with the optimization of wet or dry micro-blasting pressure by various Al2O3 grain sizes for improving the coated tool’s wear resistance. The wear behaviour of coated and variously dry or wet micro-blasted tools was investigated in milling. Considering the grains’ penetration kinematics into the coated tool surface and the film deformation mechanisms during dry or wet microblasting by fine or coarse sharp–edged Al2O3 grains, optimum process pressures can be determined.

  19. The influence of thin film grain size on the size of nanoparticles generated during UV femtosecond laser ablation of thin gold films

    International Nuclear Information System (INIS)

    Haustrup, N.; O’Connor, G.M.

    2013-01-01

    The upsurge in the number of thin film products has encouraged studies into every aspect of their fabrication and application. An additional source of industrial interest is the laser ablation of thin films to generate nanoparticles. This technique offers advantages over other fabrication methods, as no chemical pre-cursers are required, thereby giving rise to a pure product. The main disadvantage lies in the difficulty with controlling the size of the nanoparticles. This study aims to clarify the influence of the microstructure of a thin film on its optical properties and also to establish the size relationship between the film grain and the nanoparticles generated during laser ablation. A comprehensive sample set of Gold (Au) films with different grain sizes was achieved using different deposition rates, temperatures, film thicknesses (<100 nm) and substrates: Silica, Quartz and Sapphire. The microstructure of each film was analyzed using Atomic Force Microscopy (AFM). Single femtosecond laser pulses, above the ablation threshold fluence of each film, were applied to generate nanoparticles. Scanning Electron Microscopy (SEM) was used to image the re-deposited nanoparticles, from which the nanoparticle size distribution was established. Results confirm that the film microstructure is directly linked to the nanoparticles generated during laser ablation.

  20. Influence of grain size dispersion on the magnetic properties of nanogranular BaTiO3-CoFe2O4 thin films.

    Science.gov (United States)

    Barbosa, J; Almeida, B G; Mendes, J A; Leitão, D; Araújo, J P

    2009-06-01

    Thin film nanogranular composites of cobalt ferrite (CoFe2O4) dispersed in a barium titanate (BaTiO3) matrix were deposited by laser ablation with different cobalt ferrite concentrations (x). Their structural and magnetic properties were characterized. The films were polycrystalline and composed by a mixture of tetragonal-BaTiO3 and CoFe2O4 with the cubic spinel structure. A slight (111) barium titanate phase orientation and (311) CoFe2O4 phase orientation were observed. The lattice parameter of the CoFe2O4 was always smaller than the bulk value indicating that the cobalt ferrite was under compressive stress. From atomic force microscopy a broad distribution of grain sizes was observed in the nanocomposites, with a significant amount of smaller grains (magnetic measurements show an increase of the magnetic moment from the low concentration region where the magnetic grains are more isolated and their magnetic interaction is small, towards the bulk value for higher CoFe2O4 content in the films. A corresponding decrease of coercive field with increasing cobalt ferrite concentration was also observed, due to the higher inter-particle magnetic interaction (and reduced stress) of the agglomerated grains.

  1. THE FORMATION OF THE PRIMITIVE STAR SDSS J102915+172927: EFFECT OF THE DUST MASS AND THE GRAIN-SIZE DISTRIBUTION

    Energy Technology Data Exchange (ETDEWEB)

    Bovino, S.; Banerjee, R. [Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, D-21029 Hamburg (Germany); Grassi, T. [Niels Bohr Institute and Centre for Star and Planet Formation, Øster Voldgade 5-7, DK-1350 Copenhagen (Denmark); Schleicher, D. R. G., E-mail: stefano.bovino@uni-hamburg.de [Departamento de Astronomía, Facultad Ciencias Físicas y Matemáticas, Universidad de Concepción, Av. Esteban Iturra s/n Barrio Universitario, Casilla 160, Concepción (Chile)

    2016-12-01

    Understanding the formation of the extremely metal-poor star SDSS J102915+172927 is of fundamental importance to improve our knowledge on the transition between the first and second generation of stars in the universe. In this paper, we perform three-dimensional cosmological hydrodynamical simulations of dust-enriched halos during the early stages of the collapse process including a detailed treatment of the dust physics. We employ the astrochemistry package krome coupled with the hydrodynamical code enzo assuming grain-size distributions produced by the explosion of core-collapse supernovae (SNe) of 20 and 35 M {sub ⊙} primordial stars, which are suitable to reproduce the chemical pattern of the SDSS J102915+172927 star. We find that the dust mass yield produced from Population III SNe explosions is the most important factor that drives the thermal evolution and the dynamical properties of the halos. Hence, for the specific distributions relevant in this context, the composition, the dust optical properties, and the size range have only minor effects on the results due to similar cooling functions. We also show that the critical dust mass to enable fragmentation provided by semi-analytical models should be revised, as we obtain values one order of magnitude larger. This determines the transition from disk fragmentation to a more filamentary fragmentation mode, and suggests that likely more than one single SN event or efficient dust growth should be invoked to get such high dust content.

  2. Effect of Particle and Carbide Grain Sizes on a HVOAF WC-Co-Cr Coating for the Future Application on Internal Surfaces: Microstructure and Wear

    Science.gov (United States)

    Pulsford, J.; Kamnis, S.; Murray, J.; Bai, M.; Hussain, T.

    2018-01-01

    The use of nanoscale WC grain or finer feedstock particles is a possible method of improving the performance of WC-Co-Cr coatings. Finer powders are being pursued for the development of coating internal surfaces, as less thermal energy is required to melt the finer powder compared to coarse powders, permitting spraying at smaller standoff distances. Three WC-10Co-4Cr coatings, with two different powder particle sizes and two different carbide grain sizes, were sprayed using a high velocity oxy-air fuel (HVOAF) thermal spray system developed by Castolin Eutectic-Monitor Coatings Ltd., UK. Powder and coating microstructures were characterized using XRD and SEM. Fracture toughness and dry sliding wear performance at three loads were investigated using a ball-on-disk tribometer with a WC-Co counterbody. It was found that the finer powder produced the coating with the highest microhardness, but its fracture toughness was reduced due to increased decarburization compared to the other powders. The sprayed nanostructured powder had the lowest microhardness and fracture toughness of all materials tested. Unlubricated sliding wear testing at the lowest load showed the nanostructured coating performed best; however, at the highest load this coating showed the highest specific wear rates with the other two powders performing to a similar, better standard.

  3. Research on NDT Technology in Inference of Steel Member Strength Based on Macro/Micro Model

    Directory of Open Access Journals (Sweden)

    Beidou Ding

    2017-01-01

    Full Text Available In consideration of correlations among hardness, chemical composition, grain size, and strength of carbon steel, a new nondestructive testing technology (NDT of inferring the carbon steel strength was explored. First, the hardness test, chemical composition analysis, and metallographic analysis of 162 low-carbon steel samples were conducted. Second, the following works were carried out: (1 quantitative relationship between steel Leeb hardness and carbon steel strength was studied on the basis of regression analysis of experimental data; (2 influences of chemical composition and grain size on tension properties of carbon steel were analyzed on the basis of stepwise regression analysis, and quantitative relationship between conventional compositions and grain size with steel strength was obtained; (3 according to the macro and/or micro factors such as hardness, chemical compositions, and grain size of carbon steel, the fitting formula of steel strength was established based on MLR (multiple linear regressions method. The above relationships and fitting formula based on MLR method could be used to estimate the steel strength with no damage to the structure in engineering practice.

  4. 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

  5. Using UAS optical imagery and SfM photogrammetry to characterize the surface grain size of gravel bars in a braided river (Vénéon River, French Alps)

    Science.gov (United States)

    Vázquez-Tarrío, Daniel; Borgniet, Laurent; Liébault, Frédéric; Recking, Alain

    2017-05-01

    This paper explores the potential of unmanned aerial system (UAS) optical aerial imagery to characterize grain roughness and size distribution in a braided, gravel-bed river (Vénéon River, French Alps). With this aim in view, a Wolman field campaign (19 samples) and five UAS surveys were conducted over the Vénéon braided channel during summer 2015. The UAS consisted of a small quadcopter carrying a GoPro camera. Structure-from-Motion (SfM) photogrammetry was used to extract dense and accurate three-dimensional point clouds. Roughness descriptors (roughness heights, standard deviation of elevation) were computed from the SfM point clouds and were correlated with the median grain size of the Wolman samples. A strong relationship was found between UAS-SfM-derived grain roughness and Wolman grain size. The procedure employed has potential for the rapid and continuous characterization of grain size distribution in exposed bars of gravel-bed rivers. The workflow described in this paper has been successfully used to produce spatially continuous grain size information on exposed gravel bars and to explore textural changes following flow events.

  6. Effects of grain size, mineralogy, and acid-extractable grain coatings on the distribution of the fallout radionuclides 7Be, 10Be, 137Cs, and 210Pb in river sediment

    OpenAIRE

    Singleton, AA; Schmidt, AH; Bierman, PR; Rood, DH; Neilson, TB; Greene, ES; Bower, JA; Perdrial, N

    2016-01-01

    Grain-size dependencies in fallout radionuclide activity have been attributed to either increase in specific surface area in finer grain sizes or differing mineralogical abundances in different grain sizes. Here, we consider a third possibility, that the concentration and composition of grain coatings, where fallout radionuclides reside, controls their activity in fluvial sediment. We evaluated these three possible explanations in two experiments: (1) we examined the effect of sediment grain ...

  7. Effect of grain size on the sorption and desorption of SeO42- and SeO32- in columns of crushed granite and fracture infill from granitic water under dynamic conditions

    International Nuclear Information System (INIS)

    Videnska, K.; Institute of Chemical Technology, Prague; Palagyi, S.; Czech Technical University, Prague; Stamberg, K.; Vodickova, H.; Havlova, V.

    2013-01-01

    The sorption of 2 x 10 -5 mol/dm 3 Na 2 SeO 4 and Na 2 SeO 3 dissolved in synthetic granitic water (SGW) were investigated in columns of crushed granite and fracture infill (clay minerals) of various grain sizes. Desorption was studied using pure SGW. The goal of study was the quantification of the effect of grain size on the retardation and distribution coefficients of SeO 4 2- and SeO 3 2- , as well as on the other transport parameters (Peclet number and hydrodynamic dispersion coefficient). A model based on the erfc-function, assuming a non-linear reversible equilibrium sorption/desorption isotherm, was used for evaluation of sorption/desorption and transport parameters. The determination of selenium was performed using an ICP-MS technique. The experimental breakthrough curves were fitted using non-linear regression procedure, in the course of which the parameters mentioned were sought. Summing up, no sorption was recorded in the case of SeO 4 2- under these conditions. The values of retardation coefficients were practically one for all studied grain sizes. On the other hand, significant sorption was found for SeO 3 2- : depending on the grain size, the retardation coefficients varied between 1.6-8.7 in pure granite and 1.8-37.2 in infill materials. These values correspond to distribution coefficients of 0.2-2.5 and 0.2-12.7 cm 3 /g, respectively. The both parameters have similar values in a case of desorption which reflects the reversible character of sorption process. It was found that retardation and distribution coefficients and sorption capacity for SeO 3 2- also increase with decreasing grain size. (author)

  8. 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

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

    Science.gov (United States)

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

    2010-02-01

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

  10. A three dimensional two-phase debris flow model: Reduction to one free model parameter by linking rheology to grain size distribution and water content

    Science.gov (United States)

    von Boetticher, Albrecht; McArdell, Brian; Rickenmann, Dieter; Hübl, Johannes; Scheidl, Christian

    2014-05-01

    Attempts to model debris flow material either as a granular or as a viscous matter can not account for the wide range of debris flow processes, leading to the development of two-phase models with one phase accounting for the fluid and the other for the grains. Within this group of models, depth-averaged approaches are wide-spread, but since the rheology of true material is sensitive to pressure and shear gradient, three dimensional simulations are necessary to predict flows in complex geometries. Phase interaction can be modelled by solving the Navier-Stokes equation system for each phase and linking the phases with drag force models. However, this is a numerically expensive way that introduces a number of free parameters because too little is known about drag of non-spherical grains in non-Newtonian fluids. The approach proposed here solves one phase-averaged Navier-stokes equation system by applying the Volume of Fluid method, while still allowing to account for the sensitivity of the local rheology to pressure and shear in dependency to phase concentrations. One phase with a Herschel-Bulkley rheology represents the interstitial fluid and can mix with a second phase with the Coulomb-viscoplastic rheology of Pudasaini (Birte et al. 2013) that represents the gravel. A third phase is kept separate and represents the air. This setup allows modelling key properties of debris flow processes like run out or impact in high detail. By linking the Herschel Bulkley parameters to water content, clay mineral proportion and grain size distribution (Kaitna et al. 2007, Yu et al. 2013), and the parameters of the Coulomb-viscoplastic rheology to the angle of repose of the gravel, a reduction to one free model parameter was achieved. The resulting model is tested with laboratory experiments for its capability to reproduce the sensitivity of debris flow material to water content and channel curvature. Existing large scale flume experiments are used to corroborate the model and

  11. Nuclear reaction of 10 B (n, α) 7 Li and grain size effects on the production of free radicals in alanine

    International Nuclear Information System (INIS)

    Zurita Petatan, S.L.

    1993-01-01

    In general, it is important to know the physical and chemical properties of any material that is exposed to ionizing radiation. In particular, in dosimetric work, the amount of the absorbed doses by these materials is of much interest, in such a way that several methods have been developed in the past. An important and quantitatively accessible radiation effect in organic substances is the production of free radicals that can be easily measured by 'ELECTRON PARAMAGNETIC RESONANCE SPECTROSCOPY (EPR)'. Numerous studies have been now been made on pure D L-Alanine irradiated with different radiation sources. Examination of the irradiated samples reveals the production of a stable free radical (CH 3 - CH. -COOH). In particular, gamma and electron irradiated D L-Alanine has received wide attention in the high doses interval (10 - 10 5 Gy). In contrast, there are very few EPR studies on thermal neutron radiation induced free radicals in pure D L-alanine. This may be due to the weak EPR signals observed in the irradiated samples. The objective of this work is to study for the first time the increase of the radical yield produced in neutron irradiated borated alanine by the EPR technique. For this purpose alanine has been mixed with borax in different stoichiometric proportions and grain sizes. When the mixture is neutron irradiated, the boron of the borax may experience a neutron capture reaction, 10 B (n, α) 7 Li. With this nuclear reaction it is supposed that the α particles will may impinge on the alanine molecules, producing in this way extra free radicals. Samples were irradiated in the thermal column of a Triga Mark III nuclear reactor with a thermal neutron flux of 5 x 10 7 n/Cm 2 -s. A signal enhancement of up to 1260 % is observed when samples of alanine-borax were intimately mixed in a stoichiometric ratio of 1:1. We also studied dosimetric characteristics of the mixed samples such as: a) Sensibility. b) Accuracy. c) Traceability. d) Stability. e)Fading. f

  12. Quantification by image analysis of grain size of the high temperature phase (austenite) of martensitic steels 9Cr-1Mo. Quantification par analyse d'images de la taille de grain de la phase haute temperature (austenite) d'aciers martensitiques 9Cr-1Mo

    Energy Technology Data Exchange (ETDEWEB)

    Barcelo, F.; Brachet, J.C. (CEA Centre d' Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. de Technologie des Materiaux)

    1993-09-01

    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.

  13. Statistical inference

    CERN Document Server

    Rohatgi, Vijay K

    2003-01-01

    Unified treatment of probability and statistics examines and analyzes the relationship between the two fields, exploring inferential issues. Numerous problems, examples, and diagrams--some with solutions--plus clear-cut, highlighted summaries of results. Advanced undergraduate to graduate level. Contents: 1. Introduction. 2. Probability Model. 3. Probability Distributions. 4. Introduction to Statistical Inference. 5. More on Mathematical Expectation. 6. Some Discrete Models. 7. Some Continuous Models. 8. Functions of Random Variables and Random Vectors. 9. Large-Sample Theory. 10. General Meth

  14. Inferring the subsurface basement depth and the structural trends as deduced from aeromagnetic data at West Beni Suef area, Western Desert, Egypt

    Science.gov (United States)

    Khalil, Ahmed; Abdel Hafeez, Tharwat H.; Saleh, Hassan S.; Mohamed, Waheed H.

    2016-12-01

    The present work aimed to delineate the subsurface structures and to estimate the magnetic source depth at the selected area lying in West Beni Suef area, Western Desert, Egypt, following different geomagnetic techniques. The analysis of aeromagnetic data demonstrates five significant tectonic faults trending to NW-SE, ENE-WSW, NE-SW, E-W and NNW-SSE directions constructed using Euler deconvolution techniques. The execution of this study is initiated by transformation of the total intensity aeromagnetic data to the reduced to pole (RTP) magnetic intensity. This is followed by applying several transformation techniques and various filtering processes through qualitative and quantitative analyses on magnetic data. The reduced to the northern magnetic pole (RTP) data are separated spectrally into regional and residual magnetic components using the computed power spectrum of the magnetic data. The estimated mean depths of both regional and residual sources are found to be 5.27 km and 2.78 km respectively. Also, depth estimations have been conducted by application of the Euler deconvolution and 2-D modeling techniques. The results indicate that the eastern and northern parts of the study area discriminate deeper basement relief and the depth of basement surface reaches to 5095 m. While the southern and western parts of the study area discriminate shallower basement relief and the depth of basement surface reaches to 227 m. This study has given a clear picture of the geologic structures beneath the study area.

  15. Synthesis and mechanical properties of silicon-doped TiAl-alloys with grain sizes in the submicron range; Herstellung und mechanische Eigenschaften silizidhaltiger TiAl-Werkstoffe mit Korngroessen im Submikronbereich

    Energy Technology Data Exchange (ETDEWEB)

    Bohn, R. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Werkstofforschung

    1999-07-01

    The objective of this study is to provide a comprehensive insight into the mechanical properties of nano- and submicron-grained intermetallics, containing ceramic particles as a second phase. The investigations are focussed on {gamma}-TiAl-based alloys with a fine dispersion of titanium silicides. The samples are prepared by high energy milling and subsequent hot isostatic pressing. The mechanical properties are mainly dominated by the grain size as the most important structural feature. At room temperature, the grain size dependence of hardness and yield strength can be described by the well-known Hall-Petch relationship. Contrary to the behavior of conventional alloys, the ductility of submicron-grained alloys drops if the grain size is further reduced. This may be attributed to the insignificance of diffusional creep at room temperature and to arising difficulties evolving for dislocation-based deformation mechanisms. In the high temperature range, the flow stress is strongly reduced. Superplastic deformation becomes feasible already at 800 C. The silicide particles impede grain growth, but they also promote cavitation during tensile straining. The mechanisms of deformation are similar to those established for coarse-grained materials at higher temperatures ({>=}1000 C). (orig.)

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

    NARCIS (Netherlands)

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

    2014-01-01

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

  17. Effect of grain size on charge and spin correlations in Bi{sub 0.5}Ca{sub 0.5}MnO{sub 3} manganite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ade, Ramesh; Singh, Rajender, E-mail: rssp@uohyd.ernet.in

    2016-11-15

    In this work we report the electron spin resonance (ESR) and magnetization (M) studies to understand the effect of grain size (GS) on the charge ordering and spin correlations in Bi{sub 0.5}Ca{sub 0.5}MnO{sub 3} manganite synthesized by sol–gel method. The suppression of charge ordering (CO), long-range antiferromagnetic (AFM) state, shifting of ferromagnetic (FM)-cluster glass (CG) transition towards higher temperatures and evolution of different magnetic correlations with decrease in GS are discussed in view of the changes in surface to volume ratio of nano-grains. - Highlights: • Effect of grain size on charge and spin correlations in Bi{sub 0.5}Ca{sub 0.5}MnO{sub 3} are studied. • The samples with GS 27, 450 and 1080 nm were synthesized by sol–gel method. • The temperature dependent electron spin resonance (ESR) and magnetization measurements were carried out. • The evolution of different magnetic correlations with decrease in GS are ascribed to increase in surface to volume ratio of grains.

  18. Middle to Late Holocene Hydroclimate Variability on the Tibetan Plateau Inferred from a Multi-Proxy Lake Sediment Record, Galang Co, Southeastern Tibet.

    Science.gov (United States)

    Perello, M. M.; Bird, B. W.; Lei, Y.; Polissar, P. J.; Thompson, L. G.; Yao, T.

    2016-12-01

    The Indian summer monsoon (ISM) is the primary source of water for Southeastern Asia and a population of over a billion people. Reductions in rainfall and the monsoon season have the potential for dramatic impacts on regions population, but climate records for this system are limited in frequency and scale. The ISM is the primary source for the Nyainqêntanglha mountain range in eastern Tibetan Plateau producing a signal that can be construed directly to the ISM. Predicting variability in the ISM is limited when reliant on modern monitoring and as such paleoclimate records are needed to expand these records to assess long-term variability. A transect of lakes in the Nyainqêntanglha region aims to provide new Holocene era climate records that resolve ISM variability at a decadal scale. Previously unstudied lake, Galang Co, is at a relatively low elevation (2800 m) in a heavily-forested watershed in the Lhasa River valley. In contrast, most lakes studied are at higher elevations with a respective arid climate. Galang provides a more thorough analysis of how the monsoon strength varies spatially through the eastern plateau. Two Livingstone and three surface cores along with surface sediments were collected in June 2015. Basal ages show that the record spans over 7,400 years before present. Initial analyses of sediments has shown trends in sedimentology, grain size, and organic carbon matter that are inferred to represent transitions from in lake levels ranging from a shallow bog to a deep lake. This record is compared with existing paleo hydroclimate records from surrounding lakes (including Nir'Pa Co and Paru Co from this same project) to make inferences about monsoon strength and variability. Future research will incorporate terrestrial leaf-wax isotopes and diatom assemblages to expand this record. Records produced from this and similar projects have the potential to constrain climate models focusing on how the ISM will vary due to changing climate.

  19. 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

  20. SEMANTIC PATCH INFERENCE

    DEFF Research Database (Denmark)

    Andersen, Jesper

    2009-01-01

    Collateral evolution the problem of updating several library-using programs in response to API changes in the used library. In this dissertation we address the issue of understanding collateral evolutions by automatically inferring a high-level specification of the changes evident in a given set...... specifications inferred by spdiff in Linux are shown. We find that the inferred specifications concisely capture the actual collateral evolution performed in the examples....

  1. Inference in `poor` languages

    Energy Technology Data Exchange (ETDEWEB)

    Petrov, S.

    1996-10-01

    Languages with a solvable implication problem but without complete and consistent systems of inference rules (`poor` languages) are considered. The problem of existence of finite complete and consistent inference rule system for a ``poor`` language is stated independently of the language or rules syntax. Several properties of the problem arc proved. An application of results to the language of join dependencies is given.

  2. Bayesian statistical inference

    Directory of Open Access Journals (Sweden)

    Bruno De Finetti

    2017-04-01

    Full Text Available This work was translated into English and published in the volume: Bruno De Finetti, Induction and Probability, Biblioteca di Statistica, eds. P. Monari, D. Cocchi, Clueb, Bologna, 1993.Bayesian statistical Inference is one of the last fundamental philosophical papers in which we can find the essential De Finetti's approach to the statistical inference.

  3. Geometric statistical inference

    International Nuclear Information System (INIS)

    Periwal, Vipul

    1999-01-01

    A reparametrization-covariant formulation of the inverse problem of probability is explicitly solved for finite sample sizes. The inferred distribution is explicitly continuous for finite sample size. A geometric solution of the statistical inference problem in higher dimensions is outlined

  4. Practical Bayesian Inference

    Science.gov (United States)

    Bailer-Jones, Coryn A. L.

    2017-04-01

    Preface; 1. Probability basics; 2. Estimation and uncertainty; 3. Statistical models and inference; 4. Linear models, least squares, and maximum likelihood; 5. Parameter estimation: single parameter; 6. Parameter estimation: multiple parameters; 7. Approximating distributions; 8. Monte Carlo methods for inference; 9. Parameter estimation: Markov chain Monte Carlo; 10. Frequentist hypothesis testing; 11. Model comparison; 12. Dealing with more complicated problems; References; Index.

  5. Parametric statistical inference basic theory and modern approaches

    CERN Document Server

    Zacks, Shelemyahu; Tsokos, C P

    1981-01-01

    Parametric Statistical Inference: Basic Theory and Modern Approaches presents the developments and modern trends in statistical inference to students who do not have advanced mathematical and statistical preparation. The topics discussed in the book are basic and common to many fields of statistical inference and thus serve as a jumping board for in-depth study. The book is organized into eight chapters. Chapter 1 provides an overview of how the theory of statistical inference is presented in subsequent chapters. Chapter 2 briefly discusses statistical distributions and their properties. Chapt

  6. Impact of grain size and structural changes on magnetic, dielectric, electrical, impedance and modulus spectroscopic characteristics of CoFe2O4 nanoparticles synthesized by honey mediated sol-gel combustion method

    Science.gov (United States)

    Singh Yadav, Raghvendra; Kuřitka, Ivo; Vilcakova, Jarmila; Havlica, Jaromir; Masilko, Jiri; Kalina, Lukas; Tkacz, Jakub; Švec, Jiří; Enev, Vojtěch; Hajdúchová, Miroslava

    2017-12-01

    In this work CoFe2O4 spinel ferrite nanoparticles were synthesized by honey mediated sol-gel combustion method and further annealed at higher temperature 500 °C, 700 °C, 900 °C and 1100 °C. The synthesized spinel ferrite nanoparticles is investigated by x-ray diffraction, Raman spectroscopy, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis/differential scanning calorimetry (TGA/DSC), field emission scanning electron microscopy, x-ray photoelectron spectroscopy and vibrating sample magnetometer. The x-ray diffraction study reveals face-centered cubic spinel cobalt ferrite crystal phase formation. The crystallite size and lattice parameter are increased with annealing temperature. Raman and Fourier transform infrared spectra also confirm spinel ferrite crystal structure of synthesized nanoparticles. The existence of cation at octahedral and tetrahedral site in cobalt ferrite nanoparticles is confirmed by x-ray photoelectron spectroscopy. Magnetic measurement shows increased saturation magnetization 74.4 emu g-1 at higher annealing temperature 1100 °C, high coercivity 1347.3 Oe at lower annealing temperature 500 °C, and high remanent magnetization 32.3 emu g-1 at 900 °C annealing temperature. The magnetic properties of synthesized ferrite nanoparticles can be tuned by adjusting sizes through annealing temperature. Furthermore, the dielectric constant and ac conductivity shows variation with frequency (1-107 Hz), grain size and cation redistribution. The modulus spectroscopy study reveals the role of bulk grain and grain boundary towards the resistance and capacitance. The cole-cole plots in modulus formalism also well support the electrical response of nanoparticles originated from both grain and grain boundaries. The dielectric, electrical, magnetic, impedance and modulus spectroscopic characteristics of synthesized CoFe2O4 spinel ferrite nanoparticles demonstrate the applicability of these nanoparticles for magnetic recording, memory

  7. Knowledge and inference

    CERN Document Server

    Nagao, Makoto

    1990-01-01

    Knowledge and Inference discusses an important problem for software systems: How do we treat knowledge and ideas on a computer and how do we use inference to solve problems on a computer? The book talks about the problems of knowledge and inference for the purpose of merging artificial intelligence and library science. The book begins by clarifying the concept of """"knowledge"""" from many points of view, followed by a chapter on the current state of library science and the place of artificial intelligence in library science. Subsequent chapters cover central topics in the artificial intellig

  8. Logical inference and evaluation

    International Nuclear Information System (INIS)

    Perey, F.G.

    1981-01-01

    Most methodologies of evaluation currently used are based upon the theory of statistical inference. It is generally perceived that this theory is not capable of dealing satisfactorily with what are called systematic errors. Theories of logical inference should be capable of treating all of the information available, including that not involving frequency data. A theory of logical inference is presented as an extension of deductive logic via the concept of plausibility and the application of group theory. Some conclusions, based upon the application of this theory to evaluation of data, are also given

  9. NASA trend analysis procedures

    Science.gov (United States)

    1993-01-01

    This publication is primarily intended for use by NASA personnel engaged in managing or implementing trend analysis programs. 'Trend analysis' refers to the observation of current activity in the context of the past in order to infer the expected level of future activity. NASA trend analysis was divided into 5 categories: problem, performance, supportability, programmatic, and reliability. Problem trend analysis uncovers multiple occurrences of historical hardware or software problems or failures in order to focus future corrective action. Performance trend analysis observes changing levels of real-time or historical flight vehicle performance parameters such as temperatures, pressures, and flow rates as compared to specification or 'safe' limits. Supportability trend analysis assesses the adequacy of the spaceflight logistics system; example indicators are repair-turn-around time and parts stockage levels. Programmatic trend analysis uses quantitative indicators to evaluate the 'health' of NASA programs of all types. Finally, reliability trend analysis attempts to evaluate the growth of system reliability based on a decreasing rate of occurrence of hardware problems over time. Procedures for conducting all five types of trend analysis are provided in this publication, prepared through the joint efforts of the NASA Trend Analysis Working Group.

  10. Probability and Statistical Inference

    OpenAIRE

    Prosper, Harrison B.

    2006-01-01

    These lectures introduce key concepts in probability and statistical inference at a level suitable for graduate students in particle physics. Our goal is to paint as vivid a picture as possible of the concepts covered.

  11. Introductory statistical inference

    CERN Document Server

    Mukhopadhyay, Nitis

    2014-01-01

    This gracefully organized text reveals the rigorous theory of probability and statistical inference in the style of a tutorial, using worked examples, exercises, figures, tables, and computer simulations to develop and illustrate concepts. Drills and boxed summaries emphasize and reinforce important ideas and special techniques.Beginning with a review of the basic concepts and methods in probability theory, moments, and moment generating functions, the author moves to more intricate topics. Introductory Statistical Inference studies multivariate random variables, exponential families of dist

  12. Examples in parametric inference with R

    CERN Document Server

    Dixit, Ulhas Jayram

    2016-01-01

    This book discusses examples in parametric inference with R. Combining basic theory with modern approaches, it presents the latest developments and trends in statistical inference for students who do not have an advanced mathematical and statistical background. The topics discussed in the book are fundamental and common to many fields of statistical inference and thus serve as a point of departure for in-depth study. The book is divided into eight chapters: Chapter 1 provides an overview of topics on sufficiency and completeness, while Chapter 2 briefly discusses unbiased estimation. Chapter 3 focuses on the study of moments and maximum likelihood estimators, and Chapter 4 presents bounds for the variance. In Chapter 5, topics on consistent estimator are discussed. Chapter 6 discusses Bayes, while Chapter 7 studies some more powerful tests. Lastly, Chapter 8 examines unbiased and other tests. Senior undergraduate and graduate students in statistics and mathematics, and those who have taken an introductory cou...

  13. Long-term trends in Arctic and Boreal CO2 uptake from 1986 to 2007 inferred from a time dependent inversion compared with satellite NDVI observations to identify likely regions of change

    Science.gov (United States)

    Welp, L. R.; Keeling, R. F.; Patra, P. K.; Nemani, R.; Piper, S. C.

    2011-12-01

    Here we examine long-term trends in CO2 fluxes inverted from atmospheric CO2 concentrations using interannually varying reanalysis transport and seasonally variable fossil fuel emission estimates. We then compare annual and seasonal trends in CO2 fluxes with observations of 1x1 degree resolution NDVI from the AVHRR/MODIS satellite records to see where there is potential co-variance between CO2 source/sink behavior and photosynthetic activity. Temperature increases and elevated atmospheric CO2 concentrations over the last several decades have been credited with increasing vegetation growth in the high northern latitudes and increasing photosynthetic uptake of CO2 from the atmosphere. This climate-carbon negative feedback may help stabilize atmospheric CO2 and temperature. Alternatively, warming of boreal and tundra ecosystems may stimulate heterotrophic respiration more than photosynthesis leading to net CO2 release from the ecosystems to the atmosphere, switching the climate-carbon feedback to a positive, destabilizing relation, warming the planet even more. In addition, satellite evidence points to large regions of the boreal forest that were 'greening' prior to the late 1990s due to more favorable growing conditions, and regions that have been 'browning' since the late 1990s as a result of climate-induced stress or insect and fire disturbance, further decreasing the CO2 uptake potential of boreal forests. Our results show that the land zone north of 60°N, encompassing the tundra biome and excluding Europe (10°W - 63°E), had no significant long-term trend in annual CO2 uptake. The seasonal amplitude of the CO2 flux increased due to enhanced summer uptake as well as fall release, which largely canceled in the annual sum. Comparing July CO2 uptake north of 60°N from 1986 to 2007 with gridded NDVI over the same period showed the strongest correlation in the tundra of North America and Asia. The inversion analysis calculated an increase of 0.29 g C m-2 day-1

  14. Investigating the Magneto Electric Coupling of [90 wt%Na0.5Bi0.5TiO3 (NBT)-10 wt% BaFe12O19 (BaM)] novel multiferroiccomposite system by increasing of BaM grain size

    Science.gov (United States)

    Pattanayak, Ranjit; Raut, Subhajit; Kuila, Sourav; Chandrasekhar, Mallam; Panigrahi, Simanchala

    2017-02-01

    Polycrystalline three novel [90 wt%Na0.5Bi0.5TiO3 (NBT)-10 wt% BaFe12O19 (BaM)] magnetoelctricmultiferroic composite systems were fabricated by considering the variation (increasing) of BaM grain size. The desired formation of composites was confirmed by X-ray diffraction study. The FESEM and SEM study were verified the variation of grain size and 0-3 type connectivity of composite systems. To predict the room temperature multiferroicbehaviour of theses composite systems we were taken PE and MH loop. For investigating the extrinsic and intrinsic magnetoelctric effect magneto impedance spectroscopy was considered for theses composite systems. The variation of intrinsic magnetoelctric coupling was predicted by proposing a simple mechanical model.

  15. Grain-size dependence of the deterioration of oxygen transport for pure and 3 mol% Zr-doped Ba0.5Sr0.5Co0.8Fe0.2O3-δ induced by thermal annealing

    NARCIS (Netherlands)

    Saher, S.; Meffert, M.; Störmer, H.; Gerthsen, D.; Bouwmeester, Henricus J.M.

    2017-01-01

    In this study, the influence of long-term annealing at intermediate temperatures on oxygen transport of Ba0.5Sr0.5Co0.8Fe0.2O3 d (BSCF) and 3 mol% Zr-doped BSCF (BSCF-Z3) ceramics with different grain sizes was studied by means of in situ electrical conductivity relaxation (ECR) measurements.

  16. Variação do tamanho de grão da magnésia: um exemplo da complexidade de cerâmicas refratária Changing the magnesia grain size: an example of refractory ceramics complexity

    Directory of Open Access Journals (Sweden)

    M. A. L. Braulio

    2010-07-01

    Full Text Available Concretos refratários alumina-magnésia apresentam um comportamento expansivo devido à espinelização in-situ, sendo que a fonte de magnésia e o seu tamanho de grão influenciam tal reação. Neste estudo, o aumento do tamanho de grão da magnésia utilizada resultou em expansão excessiva, gerando trincamento e deteriorando as propriedades mecânicas do material. Avaliações por microscopia eletrônica de varredura indicaram microestruturas distintas para concretos contendo diferentes tamanhos de grão (The expansive behavior of alumina-magnesia refractory castable, attributed to the in-situ spinel formation, is affected by the magnesia source and its grain size. In the present work, increasing MgO grain size induced cracking, and, consequently, reduced the mechanical properties as a result of a large expansion. Scanning electron microscopy evaluations after firing at 1500 ºC showed distinct microstructures for castables containing different grain sizes (< 45 µm and < 100 µm. For the composition with finer magnesia, phases commonly detected in the literature were observed: spinel and CA6. Nevertheless, besides those two phases, the castable with the coarse magnesia also presented forsterite and monticellite around the magnesia remaining grains. Hence, the objective of this work is to analyze how the refractory castable properties could be considerably affected even by changing a single parameter: the magnesia grain size.

  17. Effects of grain size and aging conditions of fatigue crack propagation behavior in beta Ti-22V-4Al alloy; {beta} gata Ti-22V-4Al gokin no hiro kiretsu shinten kyodo ni oyobosu kessho ryukei to jiko joken no eikyo

    Energy Technology Data Exchange (ETDEWEB)

    Tokaji, K. [Gifu University, Gifu (Japan). Faculty of Engineering; Oya, K. [Daido Steel Co. Ltd., Nagoya (Japan); Kariya, H. [Aisan Industry Co. Ltd., Aichi (Japan)

    2000-11-01

    This paper presents the effect of microstructural modification on fatigue crack propagation (FCP) in a beta Ti-22V-4Al alloy. FCP experiments have been conducted using eight materials with different microstructures: two as solution treated materials (ST), three single aged materials (STA), and three two-step aged materials (STDA). Particular attention has been paid to the effect of grain size and aging condition. The results showed that in ST materials the coarse grained material exhibited higher FCP resistance than the fine grained material, but this grain size dependence was eliminated by aging, and two-step aging condition had very little influence on FCP behaviour. After allowing for crack closure, the effect of grain size was largely diminished and FCP behaviour was not affected by solution treatment temperature and aging condition. ST materials indicated the highest apparent and intrinsic FCP resistance and then STDA materials. STA materials in the decreasing order. Taking into account the difference in the modulus of elasticity in addition to crack closure, the difference in FCP resistance between STDA and STA materials was eliminated, but ST materials still showed higher FCP resistance. (author)

  18. Making Type Inference Practical

    DEFF Research Database (Denmark)

    Schwartzbach, Michael Ignatieff; Oxhøj, Nicholas; Palsberg, Jens

    1992-01-01

    We present the implementation of a type inference algorithm for untyped object-oriented programs with inheritance, assignments, and late binding. The algorithm significantly improves our previous one, presented at OOPSLA'91, since it can handle collection classes, such as List, in a useful way. A......-oriented languages practical....

  19. Type Inference with Inequalities

    DEFF Research Database (Denmark)

    Schwartzbach, Michael Ignatieff

    1991-01-01

    of (monotonic) inequalities on the types of variables and expressions. A general result about systems of inequalities over semilattices yields a solvable form. We distinguish between deciding typability (the existence of solutions) and type inference (the computation of a minimal solution). In our case, both...

  20. Inference as Prediction

    Science.gov (United States)

    Watson, Jane

    2007-01-01

    Inference, or decision making, is seen in curriculum documents as the final step in a statistical investigation. For a formal statistical enquiry this may be associated with sophisticated tests involving probability distributions. For young students without the mathematical background to perform such tests, it is still possible to draw informal…

  1. Irony as Inferred Contradiction

    Directory of Open Access Journals (Sweden)

    Лаура Альба-Хуес

    2014-12-01

    Full Text Available “If we acknowledge the existence of an Irony Principle, we should also acknowledge another ‘higher-order principle’ which has the opposite effect. While irony is an apparently friendly way of being offensive (mock politeness, the type of verbal behaviour known as ‘banter’ is an offensive way of being friendly (mock impoliteness.” Geoffrey Leech, Principles of Pragmatics (1983: 144 In this work I present some theoretical considerations about what I consider to be a permanent and ever-present feature of verbal irony, namely, inferred contradiction , which has to be distinguished from plain, direct (non-inferred contradiction as well as from indirect negation , for a contradiction which is directly expressed cannot be interpreted as ironical (since it lacks a crucial component: inference, and an indirect negation may or may not be ironic (depending on the situation, and thus cannot be considered a permanent feature of the phenomenon. In spite of the fact that many scholars have proposed different theories in order to capture the essence of this intricate and complex phenomenon, not all of them have managed to find a feature or characteristic that applies to or is found in all possible occurrences of irony. I briefly discuss the tenets of some of the best-known of these theories, namely the Classical theories (Socrates, Cicero, Quintilian, the Echoic-Mention Theory (later Echoic Theory, the Echoic Reminder Theory, the Pretence Theory and the Relevant Inappropriateness Theory, trying to show that in all the types of irony emerging from these proposals (e.g. echoic irony, pretence irony, etc. it can be observed that the irony is triggered by inferred contradiction . The one theory that according to my view and knowledge- seems to capture its whole essence to date is Attardo’s (2000 Relevant Inappropriateness Theory, to whose proposal I adhere, but I argue at the same time that inferred contradiction is another feature of irony (which

  2. Efficient Bayesian inference for ARFIMA processes

    Science.gov (United States)

    Graves, T.; Gramacy, R. B.; Franzke, C. L. E.; Watkins, N. W.

    2015-03-01

    Many geophysical quantities, like atmospheric temperature, water levels in rivers, and wind speeds, have shown evidence of long-range dependence (LRD). LRD means that these quantities experience non-trivial temporal memory, which potentially enhances their predictability, but also hampers the detection of externally forced trends. Thus, it is important to reliably identify whether or not a system exhibits LRD. In this paper we present a modern and systematic approach to the inference of LRD. Rather than Mandelbrot's fractional Gaussian noise, we use the more flexible Autoregressive Fractional Integrated Moving Average (ARFIMA) model which is widely used in time series analysis, and of increasing interest in climate science. Unlike most previous work on the inference of LRD, which is frequentist in nature, we provide a systematic treatment of Bayesian inference. In particular, we provide a new approximate likelihood for efficient parameter inference, and show how nuisance parameters (e.g. short memory effects) can be integrated over in order to focus on long memory parameters, and hypothesis testing more directly. We illustrate our new methodology on the Nile water level data, with favorable comparison to the standard estimators.

  3. Causal inference in econometrics

    CERN Document Server

    Kreinovich, Vladik; Sriboonchitta, Songsak

    2016-01-01

    This book is devoted to the analysis of causal inference which is one of the most difficult tasks in data analysis: when two phenomena are observed to be related, it is often difficult to decide whether one of them causally influences the other one, or whether these two phenomena have a common cause. This analysis is the main focus of this volume. To get a good understanding of the causal inference, it is important to have models of economic phenomena which are as accurate as possible. Because of this need, this volume also contains papers that use non-traditional economic models, such as fuzzy models and models obtained by using neural networks and data mining techniques. It also contains papers that apply different econometric models to analyze real-life economic dependencies.

  4. Stochastic processes inference theory

    CERN Document Server

    Rao, Malempati M

    2014-01-01

    This is the revised and enlarged 2nd edition of the authors’ original text, which was intended to be a modest complement to Grenander's fundamental memoir on stochastic processes and related inference theory. The present volume gives a substantial account of regression analysis, both for stochastic processes and measures, and includes recent material on Ridge regression with some unexpected applications, for example in econometrics. The first three chapters can be used for a quarter or semester graduate course on inference on stochastic processes. The remaining chapters provide more advanced material on stochastic analysis suitable for graduate seminars and discussions, leading to dissertation or research work. In general, the book will be of interest to researchers in probability theory, mathematical statistics and electrical and information theory.

  5. Multiple Instance Fuzzy Inference

    Science.gov (United States)

    2015-12-02

    and learn the fuzzy inference system’s parameters [24, 25]. In this later technique, supervised and unsupervised learning algorithms are devised to...algorithm ( unsupervised learning ) can be used to identify local contexts of the input space, and a linear classifier (supervised learning ) can be used...instance level (patch-level) labels and would require the image to be correctly segmented and labeled prior to learning . Figure 1.1: Example of an image

  6. INFERENCE BUILDING BLOCKS

    Science.gov (United States)

    2018-02-15

    whether unsupervised (such as clustering) or supervised (such as Naive Bayes). We observed the following advantages: 1 APPROVED FOR PUBLIC RELEASE...section, we explain our research in relation to DARPA’s Probabilistic Programming for Advancing Machine Learning (PPAML) program and other approaches...develop machine- learning applications by combining probabilistic models and inference techniques. On one hand, a probabilistic model is a mathematical

  7. Active inference and learning.

    Science.gov (United States)

    Friston, Karl; FitzGerald, Thomas; Rigoli, Francesco; Schwartenbeck, Philipp; O Doherty, John; Pezzulo, Giovanni

    2016-09-01

    This paper offers an active inference account of choice behaviour and learning. It focuses on the distinction between goal-directed and habitual behaviour and how they contextualise each other. We show that habits emerge naturally (and autodidactically) from sequential policy optimisation when agents are equipped with state-action policies. In active inference, behaviour has explorative (epistemic) and exploitative (pragmatic) aspects that are sensitive to ambiguity and risk respectively, where epistemic (ambiguity-resolving) behaviour enables pragmatic (reward-seeking) behaviour and the subsequent emergence of habits. Although goal-directed and habitual policies are usually associated with model-based and model-free schemes, we find the more important distinction is between belief-free and belief-based schemes. The underlying (variational) belief updating provides a comprehensive (if metaphorical) process theory for several phenomena, including the transfer of dopamine responses, reversal learning, habit formation and devaluation. Finally, we show that active inference reduces to a classical (Bellman) scheme, in the absence of ambiguity. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  8. Continuous Integrated Invariant Inference Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed project will develop a new technique for invariant inference and embed this and other current invariant inference and checking techniques in an...

  9. Multimodel inference and adaptive management

    Science.gov (United States)

    Rehme, S.E.; Powell, L.A.; Allen, Craig R.

    2011-01-01

    Ecology is an inherently complex science coping with correlated variables, nonlinear interactions and multiple scales of pattern and process, making it difficult for experiments to result in clear, strong inference. Natural resource managers, policy makers, and stakeholders rely on science to provide timely and accurate management recommendations. However, the time necessary to untangle the complexities of interactions within ecosystems is often far greater than the time available to make management decisions. One method of coping with this problem is multimodel inference. Multimodel inference assesses uncertainty by calculating likelihoods among multiple competing hypotheses, but multimodel inference results are often equivocal. Despite this, there may be pressure for ecologists to provide management recommendations regardless of the strength of their study’s inference. We reviewed papers in the Journal of Wildlife Management (JWM) and the journal Conservation Biology (CB) to quantify the prevalence of multimodel inference approaches, the resulting inference (weak versus strong), and how authors dealt with the uncertainty. Thirty-eight percent and 14%, respectively, of articles in the JWM and CB used multimodel inference approaches. Strong inference was rarely observed, with only 7% of JWM and 20% of CB articles resulting in strong inference. We found the majority of weak inference papers in both journals (59%) gave specific management recommendations. Model selection uncertainty was ignored in most recommendations for management. We suggest that adaptive management is an ideal method to resolve uncertainty when research results in weak inference.

  10. Nonparametric statistical inference

    CERN Document Server

    Gibbons, Jean Dickinson

    2010-01-01

    Overall, this remains a very fine book suitable for a graduate-level course in nonparametric statistics. I recommend it for all people interested in learning the basic ideas of nonparametric statistical inference.-Eugenia Stoimenova, Journal of Applied Statistics, June 2012… one of the best books available for a graduate (or advanced undergraduate) text for a theory course on nonparametric statistics. … a very well-written and organized book on nonparametric statistics, especially useful and recommended for teachers and graduate students.-Biometrics, 67, September 2011This excellently presente

  11. Nanotechnology and statistical inference

    Science.gov (United States)

    Vesely, Sara; Vesely, Leonardo; Vesely, Alessandro

    2017-08-01

    We discuss some problems that arise when applying statistical inference to data with the aim of disclosing new func-tionalities. A predictive model analyzes the data taken from experiments on a specific material to assess the likelihood that another product, with similar structure and properties, will exhibit the same functionality. It doesn't have much predictive power if vari-ability occurs as a consequence of a specific, non-linear behavior. We exemplify our discussion on some experiments with biased dice.

  12. Generic patch inference

    DEFF Research Database (Denmark)

    Andersen, Jesper; Lawall, Julia

    2010-01-01

    A key issue in maintaining Linux device drivers is the need to keep them up to date with respect to evolutions in Linux internal libraries. Currently, there is little tool support for performing and documenting such changes. In this paper we present a tool, spdiff, that identifies common changes...... developers can use it to extract an abstract representation of the set of changes that others have made. Our experiments on recent changes in Linux show that the inferred generic patches are more concise than the corresponding patches found in commits to the Linux source tree while being safe with respect...

  13. Foundations of Inference

    Directory of Open Access Journals (Sweden)

    Kevin H. Knuth

    2012-06-01

    Full Text Available We present a simple and clear foundation for finite inference that unites and significantly extends the approaches of Kolmogorov and Cox. Our approach is based on quantifying lattices of logical statements in a way that satisfies general lattice symmetries. With other applications such as measure theory in mind, our derivations assume minimal symmetries, relying on neither negation nor continuity nor differentiability. Each relevant symmetry corresponds to an axiom of quantification, and these axioms are used to derive a unique set of quantifying rules that form the familiar probability calculus. We also derive a unique quantification of divergence, entropy and information.

  14. Inferring horizontal gene transfer.

    Directory of Open Access Journals (Sweden)

    Matt Ravenhall

    2015-05-01

    Full Text Available Horizontal or Lateral Gene Transfer (HGT or LGT is the transmission of portions of genomic DNA between organisms through a process decoupled from vertical inheritance. In the presence of HGT events, different fragments of the genome are the result of different evolutionary histories. This can therefore complicate the investigations of evolutionary relatedness of lineages and species. Also, as HGT can bring into genomes radically different genotypes from distant lineages, or even new genes bearing new functions, it is a major source of phenotypic innovation and a mechanism of niche adaptation. For example, of particular relevance to human health is the lateral transfer of antibiotic resistance and pathogenicity determinants, leading to the emergence of pathogenic lineages. Computational identification of HGT events relies upon the investigation of sequence composition or evolutionary history of genes. Sequence composition-based ("parametric" methods search for deviations from the genomic average, whereas evolutionary history-based ("phylogenetic" approaches identify genes whose evolutionary history significantly differs from that of the host species. The evaluation and benchmarking of HGT inference methods typically rely upon simulated genomes, for which the true history is known. On real data, different methods tend to infer different HGT events, and as a result it can be difficult to ascertain all but simple and clear-cut HGT events.

  15. Statistical inferences in phylogeography

    DEFF Research Database (Denmark)

    Nielsen, Rasmus; Beaumont, Mark A

    2009-01-01

    can randomly lead to multiple different genealogies. Likewise, the same gene trees can arise under different demographic models. This problem has led to the emergence of many statistical methods for making phylogeographic inferences. A popular phylogeographic approach based on nested clade analysis...... is challenged by the fact that a certain amount of the interpretation of the data is left to the subjective choices of the user, and it has been argued that the method performs poorly in simulation studies. More rigorous statistical methods based on coalescence theory have been developed. However, these methods...... may also be challenged by computational problems or poor model choice. In this review, we will describe the development of statistical methods in phylogeographic analysis, and discuss some of the challenges facing these methods....

  16. Grain size dependent phase stabilities and presence of a monoclinic (Pm) phase in the morphotropic phase boundary region of (1−x)Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} piezoceramics

    Energy Technology Data Exchange (ETDEWEB)

    Upadhyay, Ashutosh; Singh, Akhilesh Kumar, E-mail: akhilesh-bhu@yahoo.com, E-mail: aksingh.mst@itbhu.ac.in [School of Materials Science and Technology, Indian Institute of Technology (Banaras Hindu University), Varanasi 221005 (India)

    2015-04-14

    Results of the room temperature structural studies on (1−x)Bi(Mg{sub 1/2}Ti{sub 1/2})O{sub 3}-xPbTiO{sub 3} ceramics using Rietveld analysis of the powder x-ray diffraction data in the composition range 0.28 ≤ x ≤ 0.45 are presented. The morphotropic phase boundary region exhibits coexistence of monoclinic (space group Pm) and tetragonal (space group P4 mm) phases in the composition range 0.33 ≤ x ≤ 0.40. The structure is nearly single phase monoclinic (space group Pm) in the composition range 0.28 ≤ x ≤ 0.32. The structure for the compositions with x ≥ 0.45 is found to be predominantly tetragonal with space group P4 mm. Rietveld refinement of the structure rules out the coexistence of rhombohedral and tetragonal phases in the morphotropic phase boundary region reported by earlier authors. The Rietveld structure analysis for the sample x = .35 calcined at various temperatures reveals that phase fraction of the coexisting phases in the morphotropic phase boundary region varies with grain size. The structural parameters of the two coexisting phases also change slightly with changing grain size.

  17. Admissibility of logical inference rules

    CERN Document Server

    Rybakov, VV

    1997-01-01

    The aim of this book is to present the fundamental theoretical results concerning inference rules in deductive formal systems. Primary attention is focused on: admissible or permissible inference rules the derivability of the admissible inference rules the structural completeness of logics the bases for admissible and valid inference rules. There is particular emphasis on propositional non-standard logics (primary, superintuitionistic and modal logics) but general logical consequence relations and classical first-order theories are also considered. The book is basically self-contained and

  18. Gauging Variational Inference

    Energy Technology Data Exchange (ETDEWEB)

    Chertkov, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ahn, Sungsoo [Korea Advanced Inst. Science and Technology (KAIST), Daejeon (Korea, Republic of); Shin, Jinwoo [Korea Advanced Inst. Science and Technology (KAIST), Daejeon (Korea, Republic of)

    2017-05-25

    Computing partition function is the most important statistical inference task arising in applications of Graphical Models (GM). Since it is computationally intractable, approximate methods have been used to resolve the issue in practice, where meanfield (MF) and belief propagation (BP) are arguably the most popular and successful approaches of a variational type. In this paper, we propose two new variational schemes, coined Gauged-MF (G-MF) and Gauged-BP (G-BP), improving MF and BP, respectively. Both provide lower bounds for the partition function by utilizing the so-called gauge transformation which modifies factors of GM while keeping the partition function invariant. Moreover, we prove that both G-MF and G-BP are exact for GMs with a single loop of a special structure, even though the bare MF and BP perform badly in this case. Our extensive experiments, on complete GMs of relatively small size and on large GM (up-to 300 variables) confirm that the newly proposed algorithms outperform and generalize MF and BP.

  19. Multistability and perceptual inference.

    Science.gov (United States)

    Gershman, Samuel J; Vul, Edward; Tenenbaum, Joshua B

    2012-01-01

    Ambiguous images present a challenge to the visual system: How can uncertainty about the causes of visual inputs be represented when there are multiple equally plausible causes? A Bayesian ideal observer should represent uncertainty in the form of a posterior probability distribution over causes. However, in many real-world situations, computing this distribution is intractable and requires some form of approximation. We argue that the visual system approximates the posterior over underlying causes with a set of samples and that this approximation strategy produces perceptual multistability--stochastic alternation between percepts in consciousness. Under our analysis, multistability arises from a dynamic sample-generating process that explores the posterior through stochastic diffusion, implementing a rational form of approximate Bayesian inference known as Markov chain Monte Carlo (MCMC). We examine in detail the most extensively studied form of multistability, binocular rivalry, showing how a variety of experimental phenomena--gamma-like stochastic switching, patchy percepts, fusion, and traveling waves--can be understood in terms of MCMC sampling over simple graphical models of the underlying perceptual tasks. We conjecture that the stochastic nature of spiking neurons may lend itself to implementing sample-based posterior approximations in the brain.

  20. Influência da granulometria, do diâmetro e do comprimento de amostras de grãos triturados de soja na determinação de coeficientes simultâneos de transferência Influence of soybean grain sizing and sample diameter and length on the determination of simultaneous transfer rates

    Directory of Open Access Journals (Sweden)

    Kil Jin Park

    2002-08-01

    Full Text Available Este trabalho teve como principal objetivo verificar a influência da granulometria de grãos de soja triturados, assim como do diâmetro e do comprimento do corpo-de-prova na determinação de coeficientes simultâneos de transferência de calor e massa. Utilizando-se equipamentos de coluna fechada e de coluna aberta, foram testadas três granulometrias, dois comprimentos e três diâmetros diferentes para as amostras, totalizando dezoito condições experimentais. Nos experimentos com o equipamento de coluna fechada, a maior influência na avaliação da condutividade térmica foi devida aos valores de fluxo de calor obtidos. Tanto nos experimentos de coluna fechada quanto de coluna aberta, a contribuição dos fenômenos simultâneos deve ser considerada. O comprimento e a granulometria têm influência na determinação da condutividade térmica e na difusividade mássica, ao passo que o diâmetro só interfere na obtenção do valor da difusividade mássica.The main goal of this work was to verify the influence of triturated soybean grain sizing, their sample diameters and lengths, on the determination of simultaneous heat and mass transfer rates. Using equipment with open and closed columns, three different grain sizings were tested, totalling eighteen different test conditions. For experiments with the closed column, the greater influence on the evaluation of the thermal conductivity was due to the heat flow rates. On experiments with the closed column as well as on those with the open column, the contribution of the simultaneous phenomena must be acknowledged. The sample length and the grain sizing can influence both heat conductivity and mass diffusivity, while the sample diameter interferes only with mass diffusivity rates.

  1. Trend analysis

    International Nuclear Information System (INIS)

    Smith, M.; Jones, D.R.

    1991-01-01

    The goal of exploration is to find reserves that will earn an adequate rate of return on the capital invested. Neither exploration nor economics is an exact science. The authors must therefore explore in those trends (plays) that have the highest probability of achieving this goal. Trend analysis is a technique for organizing the available data to make these strategic exploration decisions objectively and is in conformance with their goals and risk attitudes. Trend analysis differs from resource estimation in its purpose. It seeks to determine the probability of economic success for an exploration program, not the ultimate results of the total industry effort. Thus the recent past is assumed to be the best estimate of the exploration probabilities for the near future. This information is combined with economic forecasts. The computer software tools necessary for trend analysis are (1) Information data base - requirements and sources. (2) Data conditioning program - assignment to trends, correction of errors, and conversion into usable form. (3) Statistical processing program - calculation of probability of success and discovery size probability distribution. (4) Analytical processing - Monte Carlo simulation to develop the probability distribution of the economic return/investment ratio for a trend. Limited capital (short-run) effects are analyzed using the Gambler's Ruin concept in the Monte Carlo simulation and by a short-cut method. Multiple trend analysis is concerned with comparing and ranking trends, allocating funds among acceptable trends, and characterizing program risk by using risk profiles. In summary, trend analysis is a reality check for long-range exploration planning

  2. An Inference Language for Imaging

    DEFF Research Database (Denmark)

    Pedemonte, Stefano; Catana, Ciprian; Van Leemput, Koen

    2014-01-01

    We introduce iLang, a language and software framework for probabilistic inference. The iLang framework enables the definition of directed and undirected probabilistic graphical models and the automated synthesis of high performance inference algorithms for imaging applications. The iLang framework...... is composed of a set of language primitives and of an inference engine based on a message-passing system that integrates cutting-edge computational tools, including proximal algorithms and high performance Hamiltonian Markov Chain Monte Carlo techniques. A set of domain-specific highly optimized GPU...

  3. Optimization methods for logical inference

    CERN Document Server

    Chandru, Vijay

    2011-01-01

    Merging logic and mathematics in deductive inference-an innovative, cutting-edge approach. Optimization methods for logical inference? Absolutely, say Vijay Chandru and John Hooker, two major contributors to this rapidly expanding field. And even though ""solving logical inference problems with optimization methods may seem a bit like eating sauerkraut with chopsticks. . . it is the mathematical structure of a problem that determines whether an optimization model can help solve it, not the context in which the problem occurs."" Presenting powerful, proven optimization techniques for logic in

  4. Instructional Time Trends. Education Trends

    Science.gov (United States)

    Woods, Julie Rowland

    2015-01-01

    For more than 30 years, Education Commission of the States has tracked instructional time and frequently receives requests for information about policies and trends. In this Education Trends report, Education Commission of the States addresses some of the more frequent questions, including the impact of instructional time on achievement, variation…

  5. Statistical inference via fiducial methods

    OpenAIRE

    Salomé, Diemer

    1998-01-01

    In this thesis the attention is restricted to inductive reasoning using a mathematical probability model. A statistical procedure prescribes, for every theoretically possible set of data, the inference about the unknown of interest. ... Zie: Summary

  6. On principles of inductive inference

    OpenAIRE

    Kostecki, Ryszard Paweł

    2011-01-01

    We propose an intersubjective epistemic approach to foundations of probability theory and statistical inference, based on relative entropy and category theory, and aimed to bypass the mathematical and conceptual problems of existing foundational approaches.

  7. Statistical inference for stochastic processes

    National Research Council Canada - National Science Library

    Basawa, Ishwar V; Prakasa Rao, B. L. S

    1980-01-01

    The aim of this monograph is to attempt to reduce the gap between theory and applications in the area of stochastic modelling, by directing the interest of future researchers to the inference aspects...

  8. Bayesian Inference: with ecological applications

    Science.gov (United States)

    Link, William A.; Barker, Richard J.

    2010-01-01

    This text provides a mathematically rigorous yet accessible and engaging introduction to Bayesian inference with relevant examples that will be of interest to biologists working in the fields of ecology, wildlife management and environmental studies as well as students in advanced undergraduate statistics.. This text opens the door to Bayesian inference, taking advantage of modern computational efficiencies and easily accessible software to evaluate complex hierarchical models.

  9. Active inference, communication and hermeneutics.

    Science.gov (United States)

    Friston, Karl J; Frith, Christopher D

    2015-07-01

    Hermeneutics refers to interpretation and translation of text (typically ancient scriptures) but also applies to verbal and non-verbal communication. In a psychological setting it nicely frames the problem of inferring the intended content of a communication. In this paper, we offer a solution to the problem of neural hermeneutics based upon active inference. In active inference, action fulfils predictions about how we will behave (e.g., predicting we will speak). Crucially, these predictions can be used to predict both self and others--during speaking and listening respectively. Active inference mandates the suppression of prediction errors by updating an internal model that generates predictions--both at fast timescales (through perceptual inference) and slower timescales (through perceptual learning). If two agents adopt the same model, then--in principle--they can predict each other and minimise their mutual prediction errors. Heuristically, this ensures they are singing from the same hymn sheet. This paper builds upon recent work on active inference and communication to illustrate perceptual learning using simulated birdsongs. Our focus here is the neural hermeneutics implicit in learning, where communication facilitates long-term changes in generative models that are trying to predict each other. In other words, communication induces perceptual learning and enables others to (literally) change our minds and vice versa. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  10. Active inference, communication and hermeneutics☆

    Science.gov (United States)

    Friston, Karl J.; Frith, Christopher D.

    2015-01-01

    Hermeneutics refers to interpretation and translation of text (typically ancient scriptures) but also applies to verbal and non-verbal communication. In a psychological setting it nicely frames the problem of inferring the intended content of a communication. In this paper, we offer a solution to the problem of neural hermeneutics based upon active inference. In active inference, action fulfils predictions about how we will behave (e.g., predicting we will speak). Crucially, these predictions can be used to predict both self and others – during speaking and listening respectively. Active inference mandates the suppression of prediction errors by updating an internal model that generates predictions – both at fast timescales (through perceptual inference) and slower timescales (through perceptual learning). If two agents adopt the same model, then – in principle – they can predict each other and minimise their mutual prediction errors. Heuristically, this ensures they are singing from the same hymn sheet. This paper builds upon recent work on active inference and communication to illustrate perceptual learning using simulated birdsongs. Our focus here is the neural hermeneutics implicit in learning, where communication facilitates long-term changes in generative models that are trying to predict each other. In other words, communication induces perceptual learning and enables others to (literally) change our minds and vice versa. PMID:25957007

  11. Locative inferences in medical texts.

    Science.gov (United States)

    Mayer, P S; Bailey, G H; Mayer, R J; Hillis, A; Dvoracek, J E

    1987-06-01

    Medical research relies on epidemiological studies conducted on a large set of clinical records that have been collected from physicians recording individual patient observations. These clinical records are recorded for the purpose of individual care of the patient with little consideration for their use by a biostatistician interested in studying a disease over a large population. Natural language processing of clinical records for epidemiological studies must deal with temporal, locative, and conceptual issues. This makes text understanding and data extraction of clinical records an excellent area for applied research. While much has been done in making temporal or conceptual inferences in medical texts, parallel work in locative inferences has not been done. This paper examines the locative inferences as well as the integration of temporal, locative, and conceptual issues in the clinical record understanding domain by presenting an application that utilizes two key concepts in its parsing strategy--a knowledge-based parsing strategy and a minimal lexicon.

  12. Multiple sequence alignment accuracy and phylogenetic inference.

    Science.gov (United States)

    Ogden, T Heath; Rosenberg, Michael S

    2006-04-01

    Phylogenies are often thought to be more dependent upon the specifics of the sequence alignment rather than on the method of reconstruction. Simulation of sequences containing insertion and deletion events was performed in order to determine the role that alignment accuracy plays during phylogenetic inference. Data sets were simulated for pectinate, balanced, and random tree shapes under different conditions (ultrametric equal branch length, ultrametric random branch length, nonultrametric random branch length). Comparisons between hypothesized alignments and true alignments enabled determination of two measures of alignment accuracy, that of the total data set and that of individual branches. In general, our results indicate that as alignment error increases, topological accuracy decreases. This trend was much more pronounced for data sets derived from more pectinate topologies. In contrast, for balanced, ultrametric, equal branch length tree shapes, alignment inaccuracy had little average effect on tree reconstruction. These conclusions are based on average trends of many analyses under different conditions, and any one specific analysis, independent of the alignment accuracy, may recover very accurate or inaccurate topologies. Maximum likelihood and Bayesian, in general, outperformed neighbor joining and maximum parsimony in terms of tree reconstruction accuracy. Results also indicated that as the length of the branch and of the neighboring branches increase, alignment accuracy decreases, and the length of the neighboring branches is the major factor in topological accuracy. Thus, multiple-sequence alignment can be an important factor in downstream effects on topological reconstruction.

  13. Object-Oriented Type Inference

    DEFF Research Database (Denmark)

    Schwartzbach, Michael Ignatieff; Palsberg, Jens

    1991-01-01

    We present a new approach to inferring types in untyped object-oriented programs with inheritance, assignments, and late binding. It guarantees that all messages are understood, annotates the program with type information, allows polymorphic methods, and can be used as the basis of an op-timizing......We present a new approach to inferring types in untyped object-oriented programs with inheritance, assignments, and late binding. It guarantees that all messages are understood, annotates the program with type information, allows polymorphic methods, and can be used as the basis of an op...

  14. Eight challenges in phylodynamic inference

    Directory of Open Access Journals (Sweden)

    Simon D.W. Frost

    2015-03-01

    Full Text Available The field of phylodynamics, which attempts to enhance our understanding of infectious disease dynamics using pathogen phylogenies, has made great strides in the past decade. Basic epidemiological and evolutionary models are now well characterized with inferential frameworks in place. However, significant challenges remain in extending phylodynamic inference to more complex systems. These challenges include accounting for evolutionary complexities such as changing mutation rates, selection, reassortment, and recombination, as well as epidemiological complexities such as stochastic population dynamics, host population structure, and different patterns at the within-host and between-host scales. An additional challenge exists in making efficient inferences from an ever increasing corpus of sequence data.

  15. Statistical Inference for Fractional Diffusion Processes

    CERN Document Server

    Rao, B L S Prakasa

    2010-01-01

    Statistical Inference for Fractional Diffusion Processes looks at statistical inference for stochastic processes modeled by stochastic differential equations driven by fractional Brownian motion. Other related processes, such as sequential inference, nonparametric and non parametric inference and parametric estimation are also discussed. The book will deal with Fractional Diffusion Processes (FDP) in relation to statistical influence for stochastic processes. The books main focus is on parametric and non parametric inference problems for fractional diffusion processes when a complete path of t

  16. Global Trends

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Global Trends. Worldwide metro Ethernet equipment revenue hit $2.5 billion in 2002 (Infonetics Research). Projected to grow 134% to $5.9 billion by 2006 (24% CAGR). Worldwide metro Ethernet equipment ports hit 906,000 in 2002 (Infonetics Research). Will grow ...

  17. Environmental Trends.

    Science.gov (United States)

    Council on Environmental Quality, Washington, DC.

    This document consists of data which highlight trends in all sectors relevant to environmental policy. These data are presented in the form of charts and maps contained in 13 sections under the following headings: people and the land; critical areas (wetlands, wild areas, parks, historic places, and risk zones); human settlements; transportation;…

  18. Billing Trends

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Billing Trends. Internet access: Bandwidth becoming analogous to electric power. Only maximum capacity (load) is fixed; Charges based on usage (units). Leased line bandwidth: Billing analogous to phone calls. But bandwidth is variable.

  19. Food Trends.

    Science.gov (United States)

    Schwenk, Nancy E.

    1991-01-01

    An overall perspective on trends in food consumption is presented. Nutrition awareness is at an all-time high; consumption is influenced by changes in disposable income, availability of convenience foods, smaller household size, and an increasing proportion of ethnic minorities in the population. (18 references) (LB)

  20. Statistical considerations for grain-size analyses of tills

    Science.gov (United States)

    Jacobs, A.M.

    1971-01-01

    Relative percentages of sand, silt, and clay from samples of the same till unit are not identical because of different lithologies in the source areas, sorting in transport, random variation, and experimental error. Random variation and experimental error can be isolated from the other two as follows. For each particle-size class of each till unit, a standard population is determined by using a normally distributed, representative group of data. New measurements are compared with the standard population and, if they compare satisfactorily, the experimental error is not significant and random variation is within the expected range for the population. The outcome of the comparison depends on numerical criteria derived from a graphical method rather than on a more commonly used one-way analysis of variance with two treatments. If the number of samples and the standard deviation of the standard population are substituted in a t-test equation, a family of hyperbolas is generated, each of which corresponds to a specific number of subsamples taken from each new sample. The axes of the graphs of the hyperbolas are the standard deviation of new measurements (horizontal axis) and the difference between the means of the new measurements and the standard population (vertical axis). The area between the two branches of each hyperbola corresponds to a satisfactory comparison between the new measurements and the standard population. Measurements from a new sample can be tested by plotting their standard deviation vs. difference in means on axes containing a hyperbola corresponding to the specific number of subsamples used. If the point lies between the branches of the hyperbola, the measurements are considered reliable. But if the point lies outside this region, the measurements are repeated. Because the critical segment of the hyperbola is approximately a straight line parallel to the horizontal axis, the test is simplified to a comparison between the means of the standard population and the means of the subsample. The minimum number of subsamples required to prove significant variation between samples caused by different lithologies in the source areas and sorting in transport can be determined directly from the graphical method. The minimum number of subsamples required is the maximum number to be run for economy of effort. ?? 1971 Plenum Publishing Corporation.

  1. Phosphorus sorption in relation to soil grain size and geochemical ...

    African Journals Online (AJOL)

    By using stepwise regression, the combination of Al, Fe, clay and Ca predicted more than 94% of the variation in the P sorption capacity of soils samples from Simiyu and Kagera basins. These four soil properties, which are strongly related to P sorption, could therefore be used as quick tests for predicting the P sorption ...

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

    African Journals Online (AJOL)

    Mgina

    ABSTRACT. The phosphorus sorption characteristics of eight surface soil samples representative of the land use and landscape in the Simiyu and Kagera River basins were determined using the Langmuir equation. The Langmuir P adsorption maximum (Cmax) ranged from 109 to 802 mg kg-1, while. Langmuir coefficient ...

  3. Small angle neutron scattering from nanometer grain sized materials

    Science.gov (United States)

    Epperson, J. E.; Siegel, R. W.

    1991-11-01

    Small angle neutron scattering has been utilized, along with a number of complementary characterization methods suitable to the nanometer size scale, to investigate the structures of cluster-assembled nanophase materials. Results of these investigations are described and problems and opportunities in using small angle scattering for elucidating nanostructures are discussed.

  4. Wavelength-Dependent Extinction and Grain Sizes in "Dippers"

    Science.gov (United States)

    Sitko, Michael; Russell, Ray W.; Long, Zachary; Bayyari, Ammar; Assani, Korash; Grady, Carol; Lisse, Carey Michael; Marengo, Massimo; Wisniewski, John

    2018-01-01

    We have examined inter-night variability of K2-discovered "Dippers" that are not close to being viewed edge-on (as determined from previously-reported ALMA images) using the SpeX spectrograph on NASA's Infrared Telescope facility (IRTF). The three objects observed were EPIC 203850058, EPIC 205151387, and EPIC 204638512 ( = 2MASS J16042165-2130284). Using the ratio of the fluxes from 0.7-2.4 microns between two successive nights, we find that in at least two cases, the extinction increased toward shorter wavelengths. In the case of EPIC 204638512, we find that the properties of the dust differ from that seen in the diffuse interstellar medium and denser molecular clouds. However, the grain properties needed to explain the extinction does resemble those used to model the disks of many young stellar objects. The best fit to the data on EPIC 204638512 includes grains at least 500 microns in size, but lacks grains smaller than 0.25 microns. Since EPIC 204638512 is seen nearly face-on, it is possible the grains are entrained in an accretion flow that preferentially destroys the smallest grains. However, we have no indication of significant gas accretion onto the star in the form of emission lines observed in young low-mass stars. But the He I line at 1.083 microns was seen to change from night to night, and showed a P Cygni profile on one night, suggesting the gas might be outflowing from regions near the star.

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

    Indian Academy of Sciences (India)

    . Other freshwater ..... Cattle farm and aquaculture discharges: confinement. Varano. 1. 9. Medium- to fine-grained sand (150 µm) ..... Comparison of human impact across lagoons is hindered by high-scale variability of hydrographi- cal and ...

  6. Effect of aggregate grain size distribution on properties of permeable ...

    African Journals Online (AJOL)

    ) ratio on the mechanical properties of permeable concrete is investigated. The aim of this study is to prepare permeable concrete mixture with optimum properties in terms of strength and permeability. For this purpose, five different permeable ...

  7. Relationship between dynamic recrystallization, grain size distribution and rheology

    NARCIS (Netherlands)

    Heege, Johannes Hendrik ter

    2002-01-01

    The solid state flow behavior (rheology) of materials constituting the Earth’s mantle and crust is of key importance in controlling the dynamics of large scale geodynamic processes, such as mantle convection, subduction, mountain building and basin formation. Flow laws that are calibrated using

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

    Indian Academy of Sciences (India)

    fish assemblage composition, zooplankton) depend on hydrographical or geomorphological features .... fishing and extensive aquaculture (De Pippo et al. 2001). 2.2 The Lagoon of Varano (LV). LV is the largest ...... the highest abundance and the lowest diversity val- ues on an annual basis. Class 2b is distributed in.

  9. Grain size dependency in the occurrence of sand waves

    NARCIS (Netherlands)

    van der Veen, Henriëtte; Hulscher, Suzanne J.M.H.; Knaapen, Michiel

    2006-01-01

    Sandy shallow seas, like the North Sea, are very dynamic. Several morphological features are present on the bed, from small ripples to sand waves and large tidal sandbanks. The larger patterns induce significant depth variations that have an impact on human activities taking place in this area.

  10. The effect of grain size on dynamic tensile extrusion behaviour

    Directory of Open Access Journals (Sweden)

    Park Leeju

    2015-01-01

    Full Text Available Dynamic tensile extrusion (DTE tests were conducted on coarse grained and ultrafine grained (UFG OFHC Cu, Interstitial free (IF Steel, and pure Ta. Equal channel angular pressing (ECAP of 16passes with Bc for Cu, IF Steel and 4 passes for Ta was employed to fabricated UFG materials. DTE tests were carried out by launching the sphere samples (Dia. 7.62 mm to the conical extrusion die at a speed of ∼500 m/sec. The fragmentation behavior of the soft-recovered fragments were examined and compared with each other. The DTE fragmentation behavior of CG and UFG was numerically simulated by the LS-DYNA FEM code.

  11. Inference Optimization using Relational Algebra

    NARCIS (Netherlands)

    Evers, S.; Fokkinga, M.M.; Apers, Peter M.G.

    Exact inference procedures in Bayesian networks can be expressed using relational algebra; this provides a common ground for optimizations from the AI and database communities. Specifically, the ability to accomodate sparse representations of probability distributions opens up the way to optimize

  12. Mixed normal inference on multicointegration

    NARCIS (Netherlands)

    Boswijk, H.P.

    2009-01-01

    Asymptotic likelihood analysis of cointegration in I(2) models, see Johansen (1997, 2006), Boswijk (2000) and Paruolo (2000), has shown that inference on most parameters is mixed normal, implying hypothesis test statistics with an asymptotic 2 null distribution. The asymptotic distribution of the

  13. Statistical inference on variance components

    NARCIS (Netherlands)

    Verdooren, L.R.

    1988-01-01

    In several sciences but especially in animal and plant breeding, the general mixed model with fixed and random effects plays a great role. Statistical inference on variance components means tests of hypotheses about variance components, constructing confidence intervals for them, estimating them,

  14. Multi-Agent Inference in Social Networks: A Finite Population Learning Approach.

    Science.gov (United States)

    Fan, Jianqing; Tong, Xin; Zeng, Yao

    When people in a society want to make inference about some parameter, each person may want to use data collected by other people. Information (data) exchange in social networks is usually costly, so to make reliable statistical decisions, people need to trade off the benefits and costs of information acquisition. Conflicts of interests and coordination problems will arise in the process. Classical statistics does not consider people's incentives and interactions in the data collection process. To address this imperfection, this work explores multi-agent Bayesian inference problems with a game theoretic social network model. Motivated by our interest in aggregate inference at the societal level, we propose a new concept, finite population learning , to address whether with high probability, a large fraction of people in a given finite population network can make "good" inference. Serving as a foundation, this concept enables us to study the long run trend of aggregate inference quality as population grows.

  15. Industry trends

    International Nuclear Information System (INIS)

    Anon.

    1993-01-01

    This section discusses the US energy supply and demand situation including projections for energy use, the clean coal industry (constraints of regulation on investment in new technologies, technology trends, and current pollution control efficiency), opportunities in clean coal technology (Phase 2 requirements of Title 4 of the Clean Air Act, scrubber demand for lime and limestone, and demand for low sulfur coal), and the international market of clean coal technologies

  16. Bayesian inference with ecological applications

    CERN Document Server

    Link, William A

    2009-01-01

    This text is written to provide a mathematically sound but accessible and engaging introduction to Bayesian inference specifically for environmental scientists, ecologists and wildlife biologists. It emphasizes the power and usefulness of Bayesian methods in an ecological context. The advent of fast personal computers and easily available software has simplified the use of Bayesian and hierarchical models . One obstacle remains for ecologists and wildlife biologists, namely the near absence of Bayesian texts written specifically for them. The book includes many relevant examples, is supported by software and examples on a companion website and will become an essential grounding in this approach for students and research ecologists. Engagingly written text specifically designed to demystify a complex subject Examples drawn from ecology and wildlife research An essential grounding for graduate and research ecologists in the increasingly prevalent Bayesian approach to inference Companion website with analyt...

  17. Statistical inference on residual life

    CERN Document Server

    Jeong, Jong-Hyeon

    2014-01-01

    This is a monograph on the concept of residual life, which is an alternative summary measure of time-to-event data, or survival data. The mean residual life has been used for many years under the name of life expectancy, so it is a natural concept for summarizing survival or reliability data. It is also more interpretable than the popular hazard function, especially for communications between patients and physicians regarding the efficacy of a new drug in the medical field. This book reviews existing statistical methods to infer the residual life distribution. The review and comparison includes existing inference methods for mean and median, or quantile, residual life analysis through medical data examples. The concept of the residual life is also extended to competing risks analysis. The targeted audience includes biostatisticians, graduate students, and PhD (bio)statisticians. Knowledge in survival analysis at an introductory graduate level is advisable prior to reading this book.

  18. Bayesian Inference on Proportional Elections

    Science.gov (United States)

    Brunello, Gabriel Hideki Vatanabe; Nakano, Eduardo Yoshio

    2015-01-01

    Polls for majoritarian voting systems usually show estimates of the percentage of votes for each candidate. However, proportional vote systems do not necessarily guarantee the candidate with the most percentage of votes will be elected. Thus, traditional methods used in majoritarian elections cannot be applied on proportional elections. In this context, the purpose of this paper was to perform a Bayesian inference on proportional elections considering the Brazilian system of seats distribution. More specifically, a methodology to answer the probability that a given party will have representation on the chamber of deputies was developed. Inferences were made on a Bayesian scenario using the Monte Carlo simulation technique, and the developed methodology was applied on data from the Brazilian elections for Members of the Legislative Assembly and Federal Chamber of Deputies in 2010. A performance rate was also presented to evaluate the efficiency of the methodology. Calculations and simulations were carried out using the free R statistical software. PMID:25786259

  19. Nonparametric Bayesian inference in biostatistics

    CERN Document Server

    Müller, Peter

    2015-01-01

    As chapters in this book demonstrate, BNP has important uses in clinical sciences and inference for issues like unknown partitions in genomics. Nonparametric Bayesian approaches (BNP) play an ever expanding role in biostatistical inference from use in proteomics to clinical trials. Many research problems involve an abundance of data and require flexible and complex probability models beyond the traditional parametric approaches. As this book's expert contributors show, BNP approaches can be the answer. Survival Analysis, in particular survival regression, has traditionally used BNP, but BNP's potential is now very broad. This applies to important tasks like arrangement of patients into clinically meaningful subpopulations and segmenting the genome into functionally distinct regions. This book is designed to both review and introduce application areas for BNP. While existing books provide theoretical foundations, this book connects theory to practice through engaging examples and research questions. Chapters c...

  20. Statistical inference an integrated approach

    CERN Document Server

    Migon, Helio S; Louzada, Francisco

    2014-01-01

    Introduction Information The concept of probability Assessing subjective probabilities An example Linear algebra and probability Notation Outline of the bookElements of Inference Common statistical modelsLikelihood-based functions Bayes theorem Exchangeability Sufficiency and exponential family Parameter elimination Prior Distribution Entirely subjective specification Specification through functional forms Conjugacy with the exponential family Non-informative priors Hierarchical priors Estimation Introduction to decision theoryBayesian point estimation Classical point estimation Empirical Bayes estimation Comparison of estimators Interval estimation Estimation in the Normal model Approximating Methods The general problem of inference Optimization techniquesAsymptotic theory Other analytical approximations Numerical integration methods Simulation methods Hypothesis Testing Introduction Classical hypothesis testingBayesian hypothesis testing Hypothesis testing and confidence intervalsAsymptotic tests Prediction...