The impact of grain size on the hydromechanical behavior of mudstones

Lightweight cement mortars containing end-of-life tire rubber (TR) as aggregate were prepared and characterized by rheological, thermal, mechanical, microstructural, and wetting tests. The mixtures were obtained after total replacement of the conventional sand aggregate with untreated TR with different grain sizes (0–2 mm and 2–4 mm) and distributions (25%, 32%, and 40% by weight). The mortars showed lower thermal conductivities (≈90%) with respect to the sand reference due to the differences in the conductivities of the two phases associated with the low density of the aggregates and, to a minor extent, to the lack of adhesion of tire to the cement paste (evidenced by microstructural detection). In this respect, a decrease of the thermal conductivities was observed with the increase of the TR weight percentage together with a decrease of fluidity of the fresh mixture and a decrease of the mechanical strengths. The addition of expanded perlite (P, 0–1 mm grain size) to the mixture allowed us to obtain mortars with an improvement of the mechanical strengths and negligible modification of the thermal properties. Moreover, in this case, a decrease of the thermal conductivities was observed with the increase of the P/TR dosage together with a decrease of fluidity and of the mechanical strengths. TR mortars showed discrete cracks after failure without separation of the two parts of the specimens, and similar results were observed in the case of the perlite/TR samples thanks to the rubber particles bridging the crack faces. The super-elastic properties of the specimens were also observed in the impact compression tests in which the best performances of the tire and P/TR composites were evidenced by a deep groove before complete failure. Moreover, these mortars showed very low water penetration through the surface and also through the bulk of the samples thanks to the hydrophobic nature of the end-of-life aggregate, which makes these environmentally sustainable materials suitable for indoor and outdoor elements.

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Effects of oxygen content on microstructure and impact toughness of high heat input flux-cored wire weld metals

Metallurgical Research & Technology ◽

10.1051/metal/2018012 ◽

2018 ◽

Vol 115 (4) ◽

pp. 410

Author(s):

Fengyu Song ◽

Yanmei Li ◽

Ping Wang ◽

Fuxian Zhu

Keyword(s):

Grain Size ◽

Impact Toughness ◽

Weld Metal ◽

Oxygen Content ◽

Heat Input ◽

High Heat ◽

Cored Wire ◽

Weld Metals ◽

High Heat Input ◽

The Impact

Three weld metals with different oxygen contents were developed. The influence of oxygen contents on the microstructure and impact toughness of weld metal was investigated through high heat input welding tests. The results showed that a large number of fine inclusions were formed and distributed randomly in the weld metal with oxygen content of 500 ppm under the heat input condition of 341 kJ/cm. Substantial cross interlocked acicular ferritic grains were induced to generate in the vicinity of the inclusions, primarily leading to the high impact toughness at low temperature for the weld metal. With the increase of oxygen content, the number of fine inclusions distributed in the weld metal increased and the grain size of intragranular acicular ferrites decreased, which enhanced the impact toughness of the weld metal. Nevertheless, a further increase of oxygen content would contribute to a great diminution of the austenitic grain size. Following that the fraction of grain boundary and the start temperature of transformation increased, which facilitated the abundant formation of pro-eutectoid ferrites and resulted in a deteriorative impact toughness of the weld metal.

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Development of Model for Acoustic Noise Generated from Bedload in Rivers

10.5194/egusphere-egu21-9822 ◽

2021 ◽

Author(s):

Mohamad Nasr ◽

Thomas Geay ◽

Sébastien Zanker ◽

Recking Alain

Keyword(s):

Grain Size ◽

Size Distribution ◽

Impact Velocity ◽

Acoustic Noise ◽

Acoustic Power ◽

Bedload Transport ◽

Empirical Formulas ◽

Impact Rate ◽

Flux Measurements ◽

The Impact

Quantifying bedload transport is important for many applications such as river management and hydraulic structures protection. Bedload flux measurements can be achieved using physical sampler methods. However, these methods are expensive, time-consuming, and difficult to operate during high discharge events. Besides, these methods do not permit to capture the spatial and temporal variability of bedload transport flux. Recently, alternative measuring technologies have been developed to continuously monitor bedload flux and grain size distribution using passive or active sensors. Among them, the hydrophone was used to monitor bedload transport by recording the sounds generated by bedload particles colliding on the river bed (referred as self-generated noise SGN). The acoustic power of SGN was correlated with bedload flux in field experiments. To better understand these experimental results and to estimate measurement uncertainties, we developed a theoretical model to simulate the SGN. The model computes an estimation of the power spectral density (PSD)by considering the contribution of all signals generated by impacts between bedload particles and the riverbed, and accounting for the attenuation of the acoustic signal between the source and the hydrophone position due to river propagation effects,. In this model, weThe energy of acoustic noise generated from the collision between two particles is mainly dependent on the transported particles' diameter and the impact velocity. We tested different empirical formulas for the estimation of the number of impact (impact rate) and the impact velocity depending on particle size and hydraulic conditions. To characterize the acoustic power losses as a function of distance and frequency, we used an attenuation function which was experimentally calibrated for different French rivers.We tested the model on a field dataset comprising acoustic and bedload flux measurements. The results indicate that the PSD model allows estimating acoustic power (in between a range of one order of magnitude) for most of the rivers considered.&#160; The model sensitivity was evaluated. In particular, we observed that it is very sensitive to the empirical formulas used to determine the impact rate and impact speed. In addition, special attention should be kept in mind on the assumption of the grain size distribution of riverbed which can generate large variability in some rivers particularly in rivers with a significant sand fraction.

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Ionic conductivity in nanocrystalline Gd doped ceria

MRS Proceedings ◽

10.1557/proc-1122-o06-02 ◽

2008 ◽

Vol 1122 ◽

Cited By ~ 1

Author(s):

Gianguido Baldinozzi ◽

David Simeone ◽

Dominique Gosset ◽

Mickael Dollé ◽

Georgette Petot-Ervas

Keyword(s):

Grain Size ◽

Ionic Conductivity ◽

Sol Gel ◽

Doped Ceria ◽

Narrow Size Distribution ◽

Conductivity Measurements ◽

X Ray Diffraction ◽

X Ray ◽

Grain Sizes ◽

The Impact

AbstractWe have synthesized Gd-doped ceria polycrystalline samples (5, 10, 15 %mol), having relative densities exceeding 95% and grain sizes between 30 and 160 nm after axial hot pressing (750 °C, 250 MPa). The samples were prepared by sintering nanopowders obtained by sol-gel chemistry methods having a very narrow size distribution centered at about 16 nm. SEM and X-ray diffraction were performed to characterize the sample microstructures and to assess their structures. We report ionic conductivity measurements using impedance spectroscopy. It is important to investigate the properties of these systems with sub-micrometric grains and as a function of their composition. Therefore, samples having micrometric and nanometric grain sizes (and different Gd content) were studied. Evidence of Gd segregation near the grain boundaries is given and the impact on the ionic conductivity, as a function of the grain size and Gd composition, is discussed and compared to microcrystalline samples.

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Nautilus multi-grain model: Importance of cosmic-ray-induced desorption in determining the chemical abundances in the ISM

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732486 ◽

2018 ◽

Vol 615 ◽

pp. A20 ◽

Cited By ~ 9

Author(s):

Wasim Iqbal ◽

Valentine Wakelam

Keyword(s):

Grain Size ◽

Surface Temperature ◽

Gas Phase ◽

Numerical Models ◽

Cosmic Ray ◽

Grain Sizes ◽

Small Grains ◽

Grain Model ◽

Grain Surface ◽

The Impact

Context. Species abundances in the interstellar medium (ISM) strongly depend on the chemistry occurring at the surfaces of the dust grains. To describe the complexity of the chemistry, various numerical models have been constructed. In most of these models, the grains are described by a single size of 0.1 μm. Aims. We study the impact on the abundances of many species observed in the cold cores by considering several grain sizes in the Nautilus multi-grain model. Methods. We used grain sizes with radii in the range of 0.005 μm to 0.25 μm. We sampled this range in many bins. We used the previously published, MRN and WD grain size distributions to calculate the number density of grains in each bin. Other parameters such as the grain surface temperature or the cosmic-ray-induced desorption rates also vary with grain sizes. Results. We present the abundances of various molecules in the gas phase and also on the dust surface at different time intervals during the simulation. We present a comparative study of results obtained using the single grain and the multi-grain models. We also compare our results with the observed abundances in TMC-1 and L134N clouds. Conclusions. We show that the grain size, the grain size dependent surface temperature and the peak surface temperature induced by cosmic ray collisions, play key roles in determining the ice and the gas phase abundances of various molecules. We also show that the differences between the MRN and the WD models are crucial for better fitting the observed abundances in different regions in the ISM. We show that the small grains play a very important role in the enrichment of the gas phase with the species which are mainly formed on the grain surface, as non-thermal desorption induced by collisions of cosmic ray particles is very efficient on the small grains.

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The impact of language on the relationships between phonological awareness and word reading in different orthographies: A test of the psycholinguistic grain size theory in bilinguals

Applied Psycholinguistics ◽

10.1017/s0142716415000508 ◽

2015 ◽

Vol 37 (5) ◽

pp. 1083-1115 ◽

Cited By ~ 10

Author(s):

ALEXANDRA GOTTARDO ◽

ADRIAN PASQUARELLA ◽

XI CHEN ◽

GLORIA RAMIREZ

Keyword(s):

Grain Size ◽

Phonological Awareness ◽

Reading Skills ◽

Word Reading ◽

First Language ◽

Phonological Sensitivity ◽

English Reading ◽

Syllable Onset ◽

Different Orthographies ◽

The Impact

ABSTRACTThe relationships among first language (L1) and second language (L2) phonological awareness and reading skills were examined in English L2 learners with a variety of L1s, specifically Spanish, Portuguese, and Chinese (maximum N = 252). Longitudinal and concurrent relations between word reading and subcomponents of phonological awareness (i.e., syllable, onset-rime, phoneme, and, where applicable, tone awareness) were examined in kindergarten and first and second grades. The relationships between reading and specific subcomponents of phonological awareness were associated with the orthography being read, English or the L1. Phonological awareness subcomponents related to English reading were generally similar for the three English L2 groups, despite differences in the orthographies of learners’ native language. The findings support the psycholinguistic grain size theory with regard to links between phonological sensitivity and the sound–symbol correspondences used to read the specific languages.

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Effects of Cascade Reservoir Systems on the Longitudinal Distribution of Sediment Characteristics: A Case Study of the Heihe River Basin

10.21203/rs.3.rs-189115/v1 ◽

2021 ◽

Author(s):

Yu Wang ◽

Bao-long Li ◽

Juan-juan Liu ◽

Qi Feng ◽

Wei Liu ◽

...

Keyword(s):

Grain Size ◽

Sediment Transport ◽

Longitudinal Distribution ◽

Heihe River ◽

Hydrodynamic Conditions ◽

Sediment Grain Size ◽

Cascade Reservoirs ◽

Grain Size Distributions ◽

Transport Patterns ◽

The Impact

Abstract Spatial variations in grain-size parameters can reflect river sediment transport patterns and depositional dynamics. Therefore, 22 surficial sediment samples taken from the Heihe River and its cascade reservoirs were analyzed to better understand the impact of cascade reservoir construction on sediment transport patterns in inland rivers in China. The results showed that the longitudinal distribution of sediment grain size in the Heihe River was significantly affected by the influence of the cascade reservoirs. The grain size of the reservoir sediments within the cascade reservoir system was much lower than that of sediments in the natural river section, and the sediments in the natural river were well sorted, exhibiting leptokurtosis and positive or very positive skew. The lower reaches of the dammed river experienced strong erosion, and the grains of the bed sediments were coarse and poorly sorted; the grain-size distributions were more positively skewed and exhibited leptokurtosis. The backwater zone of the reservoir was influenced by both backwater and released water, and the sediment grain size was between the grain size of the natural river and that of the lower reaches of the dam; these sediments were moderately well sorted and had a positively skewed, leptokurtic grain-size distribution. Sedimentary environmental analysis revealed that the characteristics of the sediment grain size in an upstream tributary of the Heihe River were more influenced by source material than by hydrodynamic conditions, while the grain-size characteristics of the mainstream sediments were controlled mainly by hydrodynamic conditions.

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