Intermediate Grain Research Articles

Strength and dilatancy behaviors of deep sands in Shanghai with a focus on grain size and shape effect

With rapid development of infrastructures like tunnels and open excavations in Shanghai, investigations on deeper soils have become critically important. Most of the existing laboratory works were focused on the clayey strata up to Layer 6 in Shanghai, i.e. at depth of up to 40 m. In this paper, Layers 7, 9, and 11, which were mostly formed of sandy soils at depth of up to 150 m, were experimentally investigated with respect to physico-mechanical behaviors. The stress–strain behaviors were analyzed by the consolidated drained/undrained (CD/CU) triaxial tests under monotonic loading. One-dimensional (1D) oedometer tests were performed to investigate the consolidation properties of the sandy soils. Specimens were prepared at three different relative densities for each layer. Also, the micro-images and particle size analyzers were used to analyze the shape and size of the sand grains. The influences of grain size, density, and angularity on the stress–strain behaviors and compressibility were also studied. Compared to the other layers, Layer 11 had the smallest mean grain size (D50), highest compressibility, and lowest shear strength. In contrast, Layer 9 had the largest mean grain size, lowest compressibility, and highest shear strength. Layer 7 was of intermediate mean grain size, exhibiting more compressibility and less shear strength than that of Layer 9. Also, the critical state parameters and maximum dilatancy rate of different layers were discussed.

Determining Appropriate Fertilizer Scheme for Maize and Sorghum Cultivation in the Sahel Agroecological Zone of Cameroon

The objective of this study was to investigate appropriate fertilization schemes to improve the production of maize and sorghum in the Sahel agroecological zone of Cameroon. The experiment was carried out in 2018 at IRAD (Institute of Agricultural Research for Development) Kismatari experimental field. The experimental setup was a complete randomized block design in four replicates and four treatments for each crop. For maize, treatments were: T1 (No input), T2 (100 kg NPK + 100 kg Urea.ha-1), T3 (150 kg NPK + 150 kg Urea.ha-1), and T4 (200 kg NPK + 200 kg Urea.ha-1). For sorghum, treatments were: T1 (No input), T2 (50 kg NPK + 50 kg Urea.ha-1), T3 (100 kg NPK + 100 kg Urea.ha-1), and T4 (150 kg NPK + 150 kg Urea.ha-1). All fertilizer treatments NPK and urea were applied to both crops respectively at 3 and 5 weeks after sowing. Nine weeks after sowing, the plant height was highest at T3, following by T2 and T4 for the two crops. The treatment T1 exhibited the lowest grain yield while T2 and T3 showed intermediate grain yield. The treatment T4 produced the highest biomass, number of ears.plant-1, and grain yield (maize: 3.3 t. ha-1, sorghum: 2.9 t.ha-1) for the two crops and thus appears to be the most appropriate fertilizer recommendation for maize and sorghum production in the Sahel zone. However, costs-benefits studies for the use of fertilizer NPK and urea are warranted to facilitate adoption by farmers in the agroecological zone.

Registration of ‘Hilliard’ wheat

Abstract‘Hilliard’ (Reg. no. CV‐1163, PI 676271), a soft red winter (SRW) wheat (Triticum aestivum L.) developed and tested as VA11W‐108 by the Virginia Agricultural Experiment Station, was released in March 2015. Hilliard was derived from the cross ‘25R47’/‘Jamestown’. Hilliard is widely adapted, from Texas to Ontario, Canada, and provides producers with a mid‐season, medium height, awned, semi‐dwarf (Rht2) cultivar that has very high yield potential, good straw strength, and intermediate grain volume weight and quality. It expresses moderate to high levels of resistance to most diseases prevalent in the eastern United States and Ontario. In the 2016–2018 USDA‐ARS Uniform SRW Wheat nurseries, Hilliard ranked first in grain yield in the southern nursery across all 3 yr (5,147–5,758 kg ha−1). In the uniform eastern nursery, it ranked first for grain yield in 2016 (6,159 kg ha−1) and 2017 (5,633 kg ha−1) and second in 2018 (5,515 kg ha−1). Grain volume weights of Hilliard were similar to overall trial averages in the uniform southern (73.4–75.2 kg hl−1) and eastern (70–75.8 kg hl−1) nurseries. Hilliard has soft grain texture with flour softness equivalent values varying from 58.1 to 61.7 g 100 g−1. Straight grade flour yields on a Quadrumat Senior mill varied from 66.8 to 68.4 g kg−1. Flour protein concentration varied from 7.0 to 9.1 g 100 g−1 and gluten strength from 108 to 128 g 100 g−1, as measured by lactic acid solvent retention capacity. Cookie spread diameter varied from 18.3 to 18.6 cm.

The Impact of Sediment Supply on the Initiation and Magnitude of Runoff‐Generated Debris Flows

AbstractRainfall intensity‐duration (ID) thresholds are commonly used to assess the potential for runoff‐generated debris flows, but the sensitivity of these thresholds to sediment supply, which can change rapidly with time, is relatively unexplored. Furthermore, debris flows often self‐organize into distinct surges, but the factors controlling the magnitude and frequency of these surges, including sediment supply and grain size, are poorly constrained. We use a combination of numerical modeling and debris flow monitoring data from Chalk Cliffs, Colorado, USA, to explore how sediment supply influences rainfall ID thresholds for debris flows and surge properties. Results suggest that rainfall ID thresholds only become sensitive to sediment supply below a sediment thickness threshold. Surge magnitude is a nonmonotonic function of sediment supply (i.e., channel bed sediment thickness and grain size) with the largest surges tending to form at intermediate values of sediment availability with intermediate grain sizes.

UAV-based canopy textures assess changes in forest structure from long-term degradation

Degraded tropical forests dominate agricultural frontiers and their management is becoming an urgent priority. This calls for a better understanding of the different forest cover states and cost-efficient techniques to quantify the impact of degradation on forest structure. Canopy texture analyses based on Very High Spatial Resolution (VHSR) optical imagery provide proxies to assess forest structures but the mechanisms linking them with degradation have rarely been investigated. To address this gap, we used a lightweight Unmanned Aerial Vehicle (UAV) to map 739 ha of degraded forests and acquire both canopy VHSR images and height model. Thirty-three years of degradation history from Landsat archives allowed us to sample 40 plots in undisturbed, logged, over-logged and burned and regrowth forests in tropical forested landscapes (Paragominas, Pará, Brazil). Fourier (FOTO) and lacunarity textures were used to assess forest canopy structure and to build a typology linking degradation history and current states. Texture metrics capture canopy grain, heterogeneity and openness gradients and correlate with forest structure variability (R2 = 0.58). Similar structures share common degradation history and can be discriminated on the basis of canopy texture alone (accuracy = 55%). Over-logging causes a lowering in forest height, which brings homogeneous textures and of finer grain. We identified the major changes in structures due to fire following logging which changes heterogeneous and intermediate grain into coarse textures. Our findings highlight the potential of canopy texture metrics to characterize degraded forests and thus be used as indicators for forest management and degradation mitigation. Inexpensive and agile UAV open promising perspectives at the interface between field inventory and satellite characterization of forest structure using texture metrics.

Single nucleotide polymorphisms in GBBSI and SSIIa genes in relation to starch physicochemical properties in selected rice (Oryza sativa L.) varieties

Single nucleotide polymorphisms in GBBSI and SSIIa genes in relation to starch physicochemical properties in selected rice (Oryza sativa L.) varieties

Origin of superior dielectric and piezoelectric properties in 0.4Ba(Zr0.2Ti0.8)O3–0.6(Ba0.7Ca0.3)TiO3 at intermediate grain sizes

Grain size effect is one of the most important issues to develop next-generation multilayer microdevices. In this work, the tetragonal 0.4Ba(Zr0.2Ti0.8)O3–0.6(Ba0.7Ca0.3)TiO3 (BZT–60BCT) ceramics with a wide grain size from 2.1 to 24 μm were successfully prepared by using ultrafine nano powder and two-step sintering. The results demonstrate that critical/intermediate grain size of dielectric constant εr and piezoelectric constant d33 appears at ∼12.9 μm. It was found that the presence of large lattice tetragonality, and enhanced domain wall motion induced by domain coexistence between submicron and nano size in sample with a grain size of ∼12.9 μm, resulting in the superior dielectric and piezoelectric properties. These findings and analyses of the origin of superior dielectric and piezoelectric properties at intermediate grain size have important practical implications in the design of high-performance piezoelectric ceramics.

Development of Drought Tolerant Rice Variety BRRI dhan66 for Rainfed Lowland Ecosystem of Bangladesh

A newly released drought tolerant rice variety BRRI dhan66 suitable for rainfed lowland ecosystem of Bangladesh is an improvement over existing drought tolerant rice varieties. The variety has satisfactorily been passed in the proposed variety trial conducted in the farmers’ field. As a result, National Seed Board (NSB) approved this variety for commercial cultivation in the wet season (T. Aman) in 2014. It has modern plant type with 120 cm plant height and matures in 110-115 days. The important feature of this variety is higher drought tolerance during reproductive stage. It can produce 4.5-5.0 t/ha grain yield without irrigation during reproductive stage. It can produce satisfactory yield when soil moisture remains <20% and perch water table depth is more than 70-80 cm from the surface. The seed size of the variety is 24 g with intermediate long bold grain. It has long, wide and erect flag leaf with deep green colour. It is highly promising as a drought tolerant rice variety for cultivation in the drought prone area, which helps farmers’ to get rid of huge economic loss and is contributing in sustaining food security.
 Bangladesh Rice j. 2019, 23(1): 45-55

Elucidating the dual role of grain boundaries as dislocation sources and obstacles and its impact on toughness and brittle-to-ductile transition

In this paper, we resolve the role of grain boundaries on toughness and the brittle-to-ductile transition. On the one hand, grain boundaries are obstacles for dislocation glide. On the other hand, the intersection points of grain boundaries with the crack front are assumed to be preferred dislocation nucleation sites. Here, we will show that the single contributions of grain boundaries (obstacles vs. source) on toughness and the brittle-to-ductile transition are contradicting, and we will weight the single contributions by performing carefully designed numerical experiments by means of two-dimensional discrete dislocation dynamics modelling. In our parameter studies, we vary the following parameters: (i) the mean free path for dislocation glide, δ, combined with (ii) the (obstacle) force of the grain boundary, ϕ, and (iii) the dislocation source spacing along the crack front, λ. Our results show that for materials or microstructures for which the mean distance of the intersection points of grain boundaries with the crack front is the relevant measure for λ, a decrease of grain size results in an increase of toughness. The positive impact of grain boundaries outweighs the negative consequences of dislocation blocking. Furthermore, our results explain the evolving anisotropy of toughness in cold-worked metals and give further insight into the question of why the grain-size-dependent fracture toughness passes through a minimum (and the brittle-to-ductile transition temperature passes through a maximum) at an intermediate grain size. Finally, a relation of the grain-size-dependence of fracture toughness in the form of K(dδ, dλ) = KIC + kdδ0.5/dλ is deduced.

Shock-induced twinning and texture in a mild carbon steel

Deformation twinning is investigated in a polycrystalline mild steel under shock compression to about 12 GPa. The free surface velocity history is measured to calculate twinning stress. The postmortem sample is characterized with electron backscatter diffraction (EBSD). We provide a method to calculate the activated twinning systems in all twinned grains from EBSD data. Twinning is completely activated and suppressed for grain size above 36μm and below 4μm, respectively. For intermediate grain sizes (14–30μm), twinning tends to occur in the grain orientations near 〈101〉, consistent with the Schmid factor analysis. Almost all the twins nucleate on the twinning systems with the largest or second largest Schmid factors. The twinning stress is 1.16 GPa, and critical resolved shear stress for twinning is 0.47 GPa. Twinning in weakly textured sample can induce a strong 〈001〉 fiber texture, as a result of its following the Schmid’s law.

Examination of high-temperature mechanisms and behavior under compression and processing maps of pure copper

The hot compression behavior of pure copper (commercial grade) was studied in a temperature range between 843 and 993K and in a strain rate range between 10−3 and 10s−1. The activation energy for plastic flow was determined to be 215kJ/mol, which is similar to the activation energy for lattice diffusion in copper (=197kJ/mol). The stress exponent values associated with the plastic flow were 7–9, which are larger than the theoretical values associated with lattice-diffusion controlled dislocation climb creep (4.5–5). A comparison of the current data with the data obtained from the creep tests performed on the pure copper at low strain rates by other investigators in a similar temperature range revealed that the most of the data studied in this study belong to the regime where power-law breakdown occurs. Processing map constructed at a strain where steady-state plastic flow was observed showed that the power dissipation efficiency was low (≤21%) in the entire experimental ranges of strain rate and temperature. Discontinuous dynamic recrystallization (DDRX) associated with a single peak or multiple peaks in the stress-strain curves occurred during the first stage of plastic deformation. Dynamic recovery occurred after the DDRX activity ended, leading to the formation of a subgrains with low-and intermediate angle grain boundaries within the recrystallized grains with high-angle grain boundaries. Due to the formation of extensive substructure within DDRX grains, the fractions of high-angle grain boundaries measured after the compressive deformation were low (≤30%).

Find a match with triple-dating: Antarctic sub-ice zircon detritus on the modern shore of Western Australia

In this work we present a novel zircon triple-dating approach (Lu-Hf – U-Pb – (U-Th)/He), complimented with grain shape and trace element chemistry to test models of trans-continental transport of ultimately Gondwana interior derived detritus. Our integrated fingerprinting approach on single zircon grains provides the opportunity for robust source correlations as each isotopic system provides temporal constraints on distinct geological processes, ranging from source age (Lu-Hf), through crystallization age (U-Pb) to exhumation age ((U-Th)/He). Collectively, this detailed level of grain characterisation is much more diagnostic of source region than any single tracer alone, and together with grain shape, helps to constrain intermediate detrital grain histories between source and sink. Applying this approach to an enigmatic detrital zircon population from a modern beach sand on the south coast of Western Australia reveals a dominant 700-500 Ma U-Pb component, with a bimodal Hf-isotope composition and Silurian (U-Th)/He cooling age, all of which is strongly correlated with inferred sub-ice basement of East Antartica and the geodynamic setting of unexposed components of the Kuunga Orogen. Our work points towards multicycle sediment processing, and ongoing reworking of poorly known supra-Yilgarn Craton vestiges of Antarctica-derived sediment that became isolated during Cretaceous break-up of East Gondwana. Furthermore, Hf isotopes in these zircon grains suggest that the Kuunga Orogen in Antarctica was rooted on Archean crust.

Phase assemblage and properties of a nonoxide composite fabricated by a two-step gas-pressure sintering

In this work, a composite composed of [Formula: see text]-Sialon (Z[Formula: see text]=[Formula: see text]4) and ZrN has been fabricated by a two-step gas-pressure sintering method, and the effects of ZrN content and applied pressure on the phase behavior, densification and mechanical properties have been investigated. The phase behaviors were mainly dependent on the ZrN content and the applied pressure. The composites composed of [Formula: see text]-Sialon (Z[Formula: see text]=[Formula: see text]4), ZrN, 15R-Sialon (0.4 MPa) and 12H-Sialon (0.7 MPa) as major phases, with different intermediate phases depending on the ZrN content. It is revealed that with the two-step sintering technique, a higher applied gas pressure has a positive effect on mass loss, and significantly improved the mechanical properties. The addition of ZrN particles greatly helped the densification behavior, reduced the mass loss, and increased fracture toughness of the composites, but decreased hardness due to formation of intermediate phases and grain coarsening. The addition of ZrN increased the fracture toughness due to the toughening mechanisms of crack branching, crack deflection and crack bridging.

A study of magnetic retardation of iron-nickel nanopowder and sintered specimen by spark plasma

Abstract Hysteresis loss is one of the important behaviors to be considered which reverse the magnetization. In this study, the influence of alloying element, grain size, particle size and spark plasma sintering on hysteresis loss (HL) has been analyzed. An increment in the % of nickel caused a decrement in HL value at 2–100 h milling time. Generally, the value of HL decreases with the decrement of average grain size, however, the value of HL is observed to marginally increase while the average grain size decreases from 225 to 75 nm. A maximum HL value was found with the average grain size 75 nm. Hence, it could be concluded that up to a critical average grain size of ∼75 nm the HL is not strongly dependent on the average grain size, whereas lower the grain size from 75 nm the HL value steeply decreases. It indicates the high HL value can be observed at intermediate grain size and low HL value at fine and coarse grain sizes. The HL value is higher at the intermediate average size of the particle and becomes lower while the average size of the particle with a larger or smaller dimension. It was found from all spark plasma sintering samples that when milling hour increases the value of HL increases, because of the increment in sintered grain size at higher hour milled samples and also decreases the lattice imperfection and internal strain while sintering.

Effects of grain size on the chemical weathering index: A case study of Neogene fluvial sediments in southwest Japan

Grain size variation of sediments and sedimentary rocks generally complicates the assessment of the degree of chemical weathering as measured by the Chemical Index of Alteration (CIA) value. Mineralogical and geochemical research was carried out on Miocene and Pliocene fluvial sediments in southwest Japan in order to evaluate the effects of grain size on the degree of chemical weathering. A strong positive linear trend is usually exhibited between Al2O3/SiO2 ratios and quartz intensities obtained by X-ray powder diffraction, suggesting that the Al2O3/SiO2 ratio may be suitable as a grain size index for semi-consolidated and unconsolidated sediments. Most of the fine-grained sediments, for which Al2O3/SiO2 ratios are over 0.4, have higher CIA values of over 90. In contrast, coarse-grained sediments, for which Al2O3/SiO2 ratios are lower, especially below 0.2, display a wide range of CIA values. The CIA values for intermediate grain sized samples, for which Al2O3/SiO2 ratios range from 0.2 to 0.4, reflect distinctive differences in the degree of chemical weathering between Miocene and Pliocene sediments. Within this range of Al2O3/SiO2 ratios, the Miocene sediments have higher CIA values (86–98) than Pliocene sediments (71–92). To compare the degree of chemical weathering among some sediments or sedimentary rocks with variable grain sizes, it is desirable to evaluate with the Al2O3/SiO2 ratios limited to the intermediate grain size range.

Mapping and verification of grain shape QTLs based on high-throughput SNP markers in rice

Grain shape is an important trait that determines appearance quality in rice. In order to dissect the genetic basis of this complex trait, we constructed an F2 and derived F2:3 lines from a cross between a long-grain variety and one with an intermediate grain length. The F2 population was genotyped by the RICE6K array to construct a high-density linkage map. A total of 30 quantitative trait loci (QTL) for grain shape were detected over 2 years. A major QTL cluster on chromosome 7 had a strong effect on grain length and width, consistent with the effect of GL7/GW7. The other QTLs, qGL2, qGW2, and qGL12, had large effects on grain shape and were detected in both years. The effects of four QTL on seed size as well as grain yield were then validated by using BC1F6 populations derived from selected F3 plants with residual heterozygous genotypes on each QTL region. Our study indicated that the SNP array was an efficient genotyping method for QTL mapping, and the novel QTL, qGW2 and qGL12, provided insight into the genetic basis of grain shape as well as additional genetic resources for developing elite rice varieties.

Relationships between grain size and organic carbon 14C heterogeneity in continental margin sediments

The deposition and long-term burial of sedimentary organic matter (OM) on continental margins comprises a fundamental component of the global carbon cycle. A key unknown in interpretation of carbon isotope records of sedimentary OM is the extent to which OM accumulating in continental shelf and slope sediments is influenced by dispersal and redistribution processes. Here, we present results from an extensive survey of organic carbon (OC) characteristics of grain size fractions (ranging from <20 to 250 μm) retrieved from Chinese marginal sea surface sediments in order to assess the extent to which the abundance and isotope composition of OM in shallow shelf seas is influenced by hydrodynamic processes. Our findings show that contrasting relationships exist between 14C contents of OC and grain size in surface sediments associated with two different hydrodynamic modes, suggesting that transport pathways and mechanisms imparted by the different hydrodynamic conditions exert a strong influence on 14C contents of OM in continental shelf sediments. In deeper regions and erosional areas, we infer that bedload transport exerts the strongest influence on (decreases) OC 14C contents of the coarser fraction, while resuspension processes induce OC 14C depletion of intermediate grain size fractions in shallow inner-shelf settings. We use the inter-fraction spread in Δ14C values, defined here as H14, to argue that the hydrodynamic processes amplify overall 14C heterogeneity within corresponding bulk sediment samples. The magnitude and footprint of this heterogeneity carries implications for our understanding of carbon cycling in shallow marginal seas.

Texture evolution behavior and anisotropy of 2A97 Al–Li alloy during recrystallization at elevated temperature

2A97 Al–Li alloy was cold-rolled to 2 mm and then thermally exposed at different temperatures for 1 h and at 723 K for different time, respectively. The texture evolution behavior and the anisotropy of 2A97 Al–Li alloy were investigated. The result shows that the {001} 〈120〉 and {011} 〈233〉 textures are the dominant recrystallization texture. The {124} 〈211〉 texture is the final recrystallization texture. In case of low-temperature thermal exposure (473, 573 K), the {011} 〈211〉 texture is aggregated to the {112} 〈111〉 and {123} 〈634〉 textures. During the recrystallization at 723 K, the {001} 〈110〉, {111} 〈112〉 and {011} 〈100〉 textures are the intermediate transition grain orientations. The concurrent precipitation of Al20Cu2Mn3 and Al3Zr results in the occurrence of unusually sharp {011} 〈233〉 and {001} 〈120〉 texture components during recrystallization. The alloy with both recrystallization and deformation texture possesses the smallest anisotropic, and the texture is the direct reason that results in the anisotropy.

Ferroan olivine‐bearing eucrite clasts found in howardites

AbstractWe investigated several olivine‐bearing, medium‐grained, ophitic to subophitic eucritic clasts from three different Antarctic howardites. Based on grain size (0.5–2 mm), these clasts could represent intrusive igneous units. Based on mineral composition (pyroxene and plagioclase), they are similar to basaltic eucrites. Elemental concentrations of the major silicates and bulk mg#, however, range from those known for basaltic eucrites to those found in cumulate eucrites. Recognizable cumulus phases are absent. Conservatively speaking, the clasts examined may simply classify as relatively coarse‐grained unequilibrated basaltic eucrites. Alternatively, at least one of the clasts showing intermediate grain size and a relatively primitive chemical composition (mg# 50) may sample a rock type that could be genetically placed between the basaltic and cumulate eucrite lines of origin. A minor, yet genetically meaningful common feature of the clasts studied is the occurrence of fayalitic olivine. Two distinct categories exist. They are (1) fine veinlets exclusively percolating through pyroxene and (2) more substantial (up to 100 μm wide) veins and/or interstitial deposits. Only the fine veinlets also contain variable amounts of anorthite, ilmenite, and troilite. Although both types of olivine are ferroan, textural aspects suggest distinct paths of generation. The fine veinlets are best explained by decomposition of relatively FeO‐rich, heterogeneous, and locally metastable pyroxene, caused in situ by impact heating and subsequent fast cooling. The wider, often very ragged‐looking monomineralic olivine fillings, on the other hand, may represent the iron‐enriched portion of a highly fractionated magma.

Boosting energy harvesting performance in (Ba,Ca)(Ti,Zr)O3 lead-free perovskites through artificial control of intermediate grain size.

In this study, (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3 (BCTZ) lead-free ceramics with enhanced energy density were prepared by two-step sintering. All ceramics fall into the rhombohedral-orthorhombic-tetragonal (R-O-T) phase boundary near room temperature, and a dense microstructure with an intermediate grain size was observed. The enhanced piezoelectric and energy harvesting properties were attained over a wide grain size range of 10-15 μm, benefiting from the construction of the R-O-T phase boundary. Most interestingly, the maximum values of d33 and d33 × g33 (530 pC N-1 and 9720 × 10-15 m2 N-1) can be achieved at 1500/1350 °C with a grain size of 13.7 μm. The interpretation of the underlying mechanism related to domain and defect engineering has been investigated systematically. Furthermore, a high output power of 99 μW and an energy conversion efficiency of 10% were obtained at a simple cantilever energy harvester fabricated from a 1500/1350 °C specimen under an acceleration of 1.0g, making the current system very promising for piezoelectric energy harvesting applications.