scholarly journals Aeolian transportation mechanics and mass movement of surficial beach sands – a case study on Bendi-BaruvaMineral Sand Deposit, Srikakulam District, Andhra Pradesh

2021 ◽  
Vol 38 (2) ◽  
pp. 25-35
Author(s):  
Souradeep Mukherjee ◽  
Dr. A. Yugandhara Rao
Keyword(s):  
Grain Size ◽  
Mass Movement ◽  
Spherical Shape ◽  
High Water ◽  
Heavy Mineral ◽  
Wind Flow ◽  
Sand Surface ◽  
Theoretical Mass ◽  
Sand Deposit ◽  
Grain Diameter

Surficial sediment transportation studies carried out in the beach zone of Bendi-Baruva mineral sand deposit show that sand grains are transported by wind (saltation and suspension) beyond the high water line. The sand population of the study area contains heavy mineral sands (~20%) like ilmenite, garnet and sillimanite which covers 95% of the heavy mineral distribution with subordinate amounts of monazite, rutile, and zircon whereas light mineral sands (~80%) contain mostly quartz. Due to the sorted nature of these beach and dune sands the whole spectra falls within a specific range of grain size which shows a bi-modal distribution, primary mode at 0.025cm and secondary at 0.015cm. Due to this variation in density and grain size, mass of these sand particles vary resulting in differential transportation in any energy regime. In the study area, on the beach near the frontal dunes, surficial concentration of garnet grains are observed in patches having an average thickness 0.2cm i.e. around ten times of the dominant grain diameter. This surficial enrichment of garnet grains resting on a semi-uniform sand surface is the result of differential transportation of the dominant mineral grains. As more than 80% of the grain size population show a dominant grain size of 0.025cm, the wind flow parameters for the whole population is standardized with mean grain diameter (D) of 0.025cm. Mass of dominant individual minerals arrived from the grain counting technique was tallied with the theoretical mass considering spherical shape of the grains indicates a difference of mass to be within 5%. For ease of calculation and generalization the grains were considered to be spherical and their theoretical masses were taken into consideration in calculations. Considering the whole spectra of mineralogical distribution, a theoretical mass group distribution for dominant different minerals of different dominant grain sizes were formulated and total six mass groups were identified. Because quartz (~80%), ilmenite, sillimanite and garnet (together ~20%) are the most abundant, their positions were identified specifically in the theoretical mass groups and only these are considered for further discussion. To analyse wind velocity and pressure at different heights from the surface, a sediment trap was fabricated using piezo-electric sensors. A tail was attached to orient the device parallel to the wind flow so that the piezo surfaces always face the wind flow at 900 angle. The device records pressure data and converts those into voltage. Using the velocity data, macroscopic physical quantities of aeolian transportation were calculated for the study area, which empirically show the effect of mass in differential transportation of the dominant minerals that gives rise to these surficial garnet patches.

Controls on induced polarization in sandy unconsolidated sediments and application to aquifer characterization

Geophysics ◽  
2003 ◽  
Vol 68 (5) ◽  
pp. 1547-1558 ◽  
Author(s):  
L. D. Slater ◽  
D. R. Glaser
Keyword(s):  
Grain Size ◽  
Hydraulic Conductivity ◽  
Internal Surface ◽  
Ionic Mobility ◽  
Induced Polarization ◽  
Hysteretic Behavior ◽  
Degree Of Saturation ◽  
Unconsolidated Sediments ◽  
Fluid Conductivity ◽  
Grain Diameter

Resistivity and induced polarization (IP) measurements (0.1–1000 Hz) were made on clay‐free unconsolidated sediments from a sandy, alluvial aquifer in the Kansas River floodplain. The sensitivity of imaginary conductivity σ″, a fundamental IP measurement, to lithological parameters, fluid conductivity, and degree of saturation was assessed. The previously reported power law dependence of IP on surface area and grain size is clearly observed despite the narrow lithologic range encountered in this unconsolidated sedimentary sequence. The grain‐size σ″ relationship is effectively frequency independent between 0.1 and 100 Hz but depends on the representative grain diameter used. For the sediments examined here, d90, the grain diameter of the coarsest sediments in a sample, is well correlated with σ″. The distribution of the internal surface in the well‐sorted, sandy sediments investigated here is such that most of the sample weight is likely required to account for the majority of the internal surface. We find the predictive capability of the Börner model for hydraulic conductivity (K)estimation from IP measurements is limited when applied to this narrow lithologic range. The relatively weak dependence of σ″ on fluid conductivity (σw) observed for these sediments when saturated with an NaCl solution (0.06–10 S/m) is consistent with competing effects of surface charge density and surface ionic mobility on σ″ as previously inferred for sandstone. Importantly, IP parameters are a function of saturation and exhibit hysteretic behavior over a drainage and imbibition cycle. However, σ″ is less dependent than the real conductivity σ′ on saturation. In the case of evaporative drying, the σ″ saturation exponent is approximately half of the σ′ exponent. Crosshole IP imaging illustrates the potential for lithologic discrimination of unconsolidated sediments. A fining‐upward sequence correlates with an upward increase in normalized chargeability Mn, a field IP parameter proportional to σ″. The hydraulic conductivity distribution obtained from the Börner model discriminates a hydraulically conductive sand–gravel from overlying medium sand.

Effects of Continuous and Discontinuous Deposition Time in Reactive Direct Current Magnetron Sputtering of Titanium Dioxide Thin Films

2015 ◽  
Vol 1131 ◽  
pp. 251-254
Author(s):  
Montri Aiempanakit ◽  
Chantana Salawan ◽  
Kamon Aiempanakit
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Surface Morphology ◽  
Magnetron Sputtering ◽  
Direct Current ◽  
Deposition Time ◽  
Spherical Shape ◽  
Contact Angles ◽  
Water Contact ◽  
Direct Current Magnetron Sputtering

The effect of continuous and discontinuous deposition time on the properties of TiO2 thin films deposited by reactive direct current magnetron sputtering (DCMS) on glass substrates was investigated. The deposition processes were designed for a condition of continuous deposition time D1 (60 min) and three conditions of discontinuous deposition time D2 (30 min × 2 times), D3 (15 min × 4 times), and D4 (1 min × 60 times). The crystal structure, surface morphology, and hydrophilicity of TiO2 thin films were characterized by X-ray diffraction, atomic force microscope, and water contact angle method, respectively. It was found that the increasing of discontinuous deposition time (conditions from D1 to D4) shows the changing of grain size from big grain size with spherical shape to small grain size with oval shape. The crystallinity of TiO2 films decrease with increasing the discontinuous deposition time. The water contact angles also decrease as a function of increasing discontinuous deposition time. These results may be explained from the accumulation of heat on the substrate which affected the phase composition and surface morphology of TiO2 thin films.

Consolidation and properties of Gd0.1Ce0.9O1.95 nanoparticles for solid-oxide fuel cell electrolytes

2006 ◽  
Vol 21 (1) ◽  
pp. 119-124 ◽  
Author(s):  
A.I.Y. Tok ◽  
L.H. Luo ◽  
F.Y.C. Boey ◽  
J.L. Woodhead
Keyword(s):  
Grain Size ◽  
Ionic Conductivity ◽  
Sintering Temperature ◽  
Spherical Shape ◽  
Impedance Analysis ◽  
Lattice Parameter ◽  
Narrow Particle Size Distribution ◽  
Precipitation Process ◽  
Boundary Area ◽  
Co Precipitation

Gd-doped ceria solid solutions have been recognized to be leading electrolytes for use in intermediate-temperature fuel cells. In this paper, the preparation, solubility, and densification of Gd0.1Ce0.9O1.95 ceramics derived from carbonate co-precipitation are reported. The dissolution of Gd2O3 in CeO2 lattice was identified to be completed during the co-precipitation process by studying the lattice parameter as a function of temperature. After calcination at 800 °C for 2 h, the nano-sized Gd0.1Ce0.9O1.95 powder (∼33 nm) with a nearly spherical shape and a narrow particle-size distribution was obtained. This calcined powder has high sinterability and maximum densification rate at ∼1000 °C. Sintering at 1300 °C for 4 h yielded over 97% relative density with near maximum. The grain size increased with increases in sintering temperature. The ionic conductivity of these pellets was tested by alternating current impedance spectroscopy to elucidate the contribution of intragranular and intergranular conductivity to the total ionic conductivity. It was found that sintering temperature does not affect intragranular conductivity, though intergranular conductivity was strongly influenced by grain size, grain boundary area, and relativity density. This pellet sintered at 1500 °C for 4 h showed a high ionic conductivity of 5.90 × 10−2 s/cm when measured at 750 °C. The characterization and structural evaluation of the as-received powders were carried out using x-ray diffraction, transmission electron microscopy, Brunauer–Emmett–Teller, and dilatometer and impedance analysis.

Effects of episodic sediment supply on experimental step-pool channel morphology, bedload transport and channel stability

2021 ◽  
Author(s):  
Jiamei Wang ◽  
Marwan A. Hassan ◽  
Matteo Saletti ◽  
Xingyu Chen ◽  
Xudong Fu ◽  
...  
Keyword(s):  
Grain Size ◽  
Morphological Changes ◽  
Mass Movement ◽  
Channel Morphology ◽  
Bedload Transport ◽  
Sediment Supply ◽  
Primary Control ◽  
Channel Stability ◽  
Flume Experiments ◽  
Small Magnitude

<p>Steep step-pool streams are often coupled to adjacent hillslope, directly receiving episodic sediment supply from mass movement processes such as landslides and debris flows. The response of step-pool channels to the variations in sediment supply remains largely unexplored. We conducted flume experiments with a poorly sorted grain-size distribution in an 8%-steep, 5-m long flume with variable width at the University of British Columbia, to study the effects of episodic sediment supply on channel evolution. After a conditioning phase with no feed, the channel was subjected to sediment pulses of different magnitude and frequency under constant flow discharge. High-resolution data of hydraulics, bedload transport, bed surface grain size, and channel morphology were collected every 10-20 minutes and an additional time at the end of each pulse.</p><p>In response to sediment pulses, we recorded an increase in bedload transport rates, channel aggradation, bed surface fining, and continuous step formation and collapse. In between pulses, bedload rates dropped by several orders of magnitude, net erosion occurred, the bed surface gradually coarsened, and steps became more stable. The small-magnitude high-frequency pulses caused smaller but more frequent spikes in bedload transport, bed surface evolution, and thus step stability. Instead, the large-magnitude low-frequency pulses cause larger changes but provided a longer time for the channel to recover. This suggests that in step-pool channels pulse magnitude is a key control on channel rearrangement, while pulse frequency controls how fast and strong the recovery is.</p><p>The frequency and stability of steps varied as a function of local channel width, showing that channel geometry is a primary control on step formation and stability even under episodic sediment supply conditions. Instead, the effect of sediment pulses is less important because the total number and average survival time of steps were similar among runs with different pulses. The critical Shields stress decreased following sediment pulses, then increased immediately after, and fluctuated until the next pulse. The variations in sediment supply caused cycles in bedload transport rate, surface and bedload texture, thus controlling the variability in the threshold for motion.</p><p>Our results indicate that episodic sediment supply is a primary control on the evolution of step-pool channels, with sediment feed magnitude affecting mostly morphological changes, and sediment feed frequency controlling channel stability.</p>

Zum Kornwachstum beim reinen und dotierten polykristallinen Selen / Grain Growth of Pure and Doped Poly crystalline Selenium

1971 ◽  
Vol 26 (7) ◽  
pp. 1198-1201
Author(s):  
C. Weyrich
Keyword(s):  
Electrical Conductivity ◽  
Grain Size ◽  
Grain Growth ◽  
Annealing Time ◽  
High Purity ◽  
The Mean ◽  
Grain Surface ◽  
Polycrystalline Form ◽  
Grain Diameter

Abstract Grain Growth of Pure and Doped Poly crystalline Selenium Samples of vitreous high-purity selenium as well as vitreous chlorine-and thallium-doped selenium have been brought into the polycrystalline form by annealing. The dependence of grain size on annealing time tu was measured. In high-purity selenium and in chlorine-doped selenium the mean grain diameter increases essentially ~ tu1/2 , in thallium-doped selenium ~ tu1/2 , as is expected from the laws of grain growth. The proportionality between electrical conductivity and specific grain surface reported by other authors could not be verified.

scholarly journals Heavy Mineral Variability in the Yellow River Sediments as Determined by the Multiple-Window Strategy

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 85 ◽  
Author(s):  
Bingfu Jin ◽  
Mengyao Wang ◽  
Wei Yue ◽  
Lina Zhang ◽  
Yanjun Wang
Keyword(s):  
Particle Size ◽  
Grain Size ◽  
Yellow River ◽  
River Sediments ◽  
Size Fraction ◽  
Heavy Mineral ◽  
The Yellow River ◽  
Yellow River Sediment ◽  
Yellow River Sediments ◽  
End Members

In this study, heavy mineral analysis was carried out in different size fractions of the Yellow River sediment to extract its end-members. It shows that heavy mineral contents, species, and compositions vary in different grain sizes. Distribution curve of heavy mineral concentration (HMC) and particle size frequency curve are in normal distribution. In most samples, the size fraction of 4.5–5.0 Φ contains the maximum HMC (18% on average). Heavy mineral assemblages of the Yellow River are featured by amphibole + epidote + limonite + garnet. Amphibole content is high in coarse fraction of >3.0 Φ and reaches its peak value in 3.5–4.5 Φ. Epidote is rich in a size fraction of >3.5 Φ, and increase as the particle size becomes fine. Micas content is high in coarse subsamples of <3.0 Φ, but almost absent in fine grains of >4.0 Φ. Metallic minerals (magnetite, ilmenite, hematite, and limonite) increase as the sediment particle size become fine, and reach the peak in silt (>4.0 Φ). Other minerals such as zircon, rutile, tourmaline, garnet, and apatite account for about 15%, and mainly concentrate in fine sediment. Further analysis reveals that similarity value between the most abundant grain size group and wide window grain size group is high (0.978 on average). The grain size of 4.0–5.0 Φ ± 0.5 Φ is suitable to carry out detrital mineral analysis in the Yellow River sediments. Our study helps to eliminate cognitive bias due to narrow grain size strategy, and to provide heavy mineral end-members of the Yellow River sediment for provenance discrimination in the marginal seas of East China.

scholarly journals Effect of Grain Size on the Microstructure and Strain Hardening Behavior of Solution Heat-Treated Low-C High-Mn Steel

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1489 ◽  
Author(s):  
Marek Opiela ◽  
Gabriela Fojt-Dymara ◽  
Adam Grajcar ◽  
Wojciech Borek
Keyword(s):  
Grain Size ◽  
Strain Hardening ◽  
Strengthening Mechanism ◽  
Strength Properties ◽  
Low Carbon ◽  
Premature Failure ◽  
Hardening Behavior ◽  
Heat Treated ◽  
Strain Hardening Behavior ◽  
Grain Diameter

The low-carbon high-Mn austenitic steel microalloyed with titanium was investigated in this work. The steel was solution heat-treated at different temperatures in a range from 900 to 1200 °C. The aim was to receive a different grain size before the static tensile test performed at room temperature. The samples of different grain sizes showed the different strain hardening behavior and resulting mechanical properties. The size of grain diameter below 19 μm was stable up to 1000 °C. Above this temperature, the very enhanced grain growth took place with the grain diameter higher than 220 μm at 1200 °C. This huge grain size at the highest temperature resulted in the premature failure of the sample showing the lowest strength properties at the same time. Correlations between the grain size, the major strengthening mechanism, and fracture behavior were addressed. The relationships were assessed based on microstructural investigations and fractography tests performed for the deformed samples. The best combination of strength and ductility was found for the samples treated at 1000–1100 °C.

COSMIC RAY PHENOMENA AT MINIMUM IONIZATION IN A NEW NUCLEAR EMULSION HAVING A FINE GRAIN, MADE IN THE LABORATORY

1954 ◽  
Vol 32 (8) ◽  
pp. 538-554 ◽  
Author(s):  
Pierre Demers
Keyword(s):  
Grain Size ◽  
Nuclear Emulsion ◽  
Electron Pair ◽  
Cosmic Ray ◽  
Silver Bromide ◽  
Positive Identification ◽  
Fine Grain ◽  
Scattering Measurements ◽  
Made In ◽  
Grain Diameter

The preparation of a silver bromide emulsion in the form of baseless sheets and their use in thick homogeneous stacks are described. In these sheets, a suitable development brings out minimum ionization tracks with a grain diameter 0.1 to 0.2 μ, and a linear grain density of 15 per 100 μ. The sequence of observations which led to the positive identification of minimum tracks is discussed. Short recoils and delta rays are visible, and excellent discrimination is available at all ionizing powers. The influence of grain size on fog is analyzed.Several cosmic ray phenomena containing minimum tracks are presented: single tracks, hard showers, πμe events, and an electron pair. Distortion is very small, and it is shown that the small grain size renders feasible better scattering measurements on higher energy particles. With this emulsion, nearly every possible measurement should become feasible with greater accuracy.

scholarly journals The movement of desert sand

1936 ◽  
Vol 157 (892) ◽  
pp. 594-620 ◽  
Keyword(s):  
Grain Size ◽  
Wind Velocity ◽  
Mass Movement ◽  
Mechanical Analysis ◽  
Sand Beach ◽  
Desert Sand ◽  
Eolian Sand ◽  
Percentage Weight ◽  
Surface Sand ◽  
Quartz Grains

It is well known that on a dry sand beach and, on a much larger scale, on sand-strewn desert country the wind, if above a certain strength, will cause the surface sand grains to rise and to travel down-wind as a low-flying cloud. The mechanism, however, by which ( a ) the grains composing this cloud are raised, ( b ) the rate of mass movement of the sand depends upon the wind velocity, or ( c ) the wind velocity close to the surface is affected by the presence of the sand cloud, does not appear to have been previously investigated experimentally. This mutual interaction of wind and sand grains is of interest both in connexion with the problem of the tendency of sand to heap itself up into dunes even in totally flat uniform plains, and also for the light it may throw on certain aspects of the allied problem of the transport of sediment by liquid currents. Sand found in the desert is usually composed of rounded quartz grains whose sizes range from small pebbles 2 to 3 mm. in diameter down to small particles 0∙01 mm. in diameter, which must be regarded as dust. Mechanical analysis of eolian sand for grain size show, when curves of percentage weight are plotted against grain size, that the peaks of such curves never occur on the small side of 0∙15 mm. diameter. Sand having this smallest peak size is found at the crests of dunes. Here the grains approach uniformity of size, so that the diagrams are sharp-peaked. On the other hand, sand deposits clear of the actual dunes give broad, low diagrams with the peak at a larger diameter. In every case the diagrams show only a few per cent by weight at a size of 0∙03 mm. In fact, it is a peculiarity of all sand accumulations that they are practically free from dust.

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