Relative Grain Size Research Articles

Impact of temporal beach grain size variability on aeolian sediment transport and topographic evolution in a microtidal environment

While the impact of the spatio/temporal variability of grain size on morphological beach state is reasonably well understood, relatively little is known on its impact at a scale of days/months on aeolian sediment transport. This study focuses on five short intensive wind events during which aeolian sediment transport measurements, beach surface sampling and elevation change surveys were carried out for 1 to 3 days, over a 16-month period on a microtidal beach dominated by offshore winds. Monthly observations show a high temporal variability in beach grain size in relation to the decoupling between hydrodynamic and aeolian processes, from medium sand after a marine storm and inundation of the beach, to very coarse sand after several weeks of storm-force winds. During each wind event, topographic change on the beach ranged from zero, to 0.55 m. The time scale of coarsening depended on the initial beach grain size and could be very fast when the beach was composed of medium sand (e.g. 388 μm sand changed to coarse sand of 547 μm in 40 h). In contrast, it took one month to transition from a coarse median beach grain size of 883 μm to a very coarse one of 1323 μm. This variability in grain size results in dramatically different rates of sediment flux. For example, during average wind speeds of 10 to 14 m/s the sediment flux when the beach was composed of medium sized sand ranged between 21 and 154 kg/m/h compared to 0.4 to 50 kg/m/h when the beach was composed of coarse and very coarse sized grains. Overall, this study highlights the importance of beach grain size variability on aeolian sediment transport and shows that for similar incident wind and climatic conditions aeolian sediment transport rates vary dramatically. The study demonstrates the importance of taking care when using a constant median grain size in the calculation of long-term aeolian sand transport on beaches with heterogeneous spatial and temporal beach grain size variability.

On the Influence of Grain Size Compared with Other Internal Factors Affecting the Permeability of Granular Porous Media: Redefining the Permeability Units

Abstract This study first reviews the influence of grain size on the permeability of porous granular media in comparison to other factors, especially the sorting of grain size distribution, in order to improve the physical knowledge of permeability. The aim of this research is to counter the widespread misconception that the characteristics of water flow in granular porous media can be associated exclusively with an area regarding grain size. This review involves two different aspects. First, the dependence of the intrinsic permeability on the particle size distribution is highlighted, independently of the other internal factors such as porosity and average grain size, by simply reviewing the main existing formulas. Second, the historical literature on the influence of the average grain size in porosity is analyzed, and it is compared with the influence of the granulometric sorting. The most recognized data show that the influence of each of these two factors is of the same order, but it was not expressed in mathematical form, so a relationship of porosity versus average grain size and sorting is established. The two aforementioned steps conclude that the factors influencing permeability do not advise the use of area dimensions because it leads to only link permeability with the average grain size, especially when nonspecialists come into contact with earth sciences. Finally, after a review of the historical evolution of the permeability units, they are redefined to avoid the common misconception that occurs when the established unit leads to only a partial understanding of the key parameters influencing permeability.

Water Use Efficiency, Spectral Phenotyping and Protein Composition of Two Chickpea Genotypes Grown in Mediterranean Environments under Different Water and Nitrogen Supply

Chickpea is a drought-tolerant crop and an important source of protein, relevant to its beneficial effects. The aim of this study was to assess the response to agronomic management, including water and nitrogen supply, of crop physiological and agronomic traits in relation to water use efficiency and grain protein composition. Two varieties, Pascià and Sultano, were grown at two different sites in South Italy under rainfed and irrigated conditions, with and without starter nitrogen fertilization. Crop physiological assessment was carried out by hyperspectral phenotyping at flowering and during grain filling. Increases in grain yield and grain size in relation to water supply were observed for water use up to about 400 mm. Water use efficiency increased under starter nitrogen fertilization, and Pascià showed the highest values (4.8 kg mm−1). The highest correlations of the vegetation indexes with the agronomic traits were observed in the later growth stage, especially for the optimized soil-adjusted vegetation index (OSAVI); furthermore, grain filling rate showed a strong relationship with photochemical reflectance index (PRI). Experimental factors mainly influenced protein composition rather than protein content. In particular, the 7s vicilin protein fraction showed a negative correlation with grain yield and water use, while lectin showed an opposite response. Both fractions are of interest for consumer’s health because of their allergenic and antinutritional properties, respectively. Data from spectral phenotyping will be useful for digital farming applications, in order to assess crop physiological status in modern agricultural systems.

Effect of Cooling Rate on Phase Transformation Kinetics and Microstructure of Nb–Ti Microalloyed Low Carbon HSLA Steel

Nb–Ti microalloyed low carbon high strength low alloy (HSLA) steels are used to fabricate components, particularly for the automobile and piping applications requiring optimum combination of mechanical properties along with good weldability. These properties depend on the transformed ferrite microstructure and grain size obtained after cooling from hot rolling temperatures which are always well above the austenitizing temperature. Hence, an attempt was made to study the austenite decomposition (phase transformation) kinetics and the accompanying microstructural evolution in Nb–Ti microalloyed steel by subjecting it to austenitization at 1100 °C for 3 min followed by cooling at different rates ranging from 1 to 100 °C/sec in a B\(\ddot{a}\)hr DIL 805 A/D dilatometer. The first derivative method was employed to identify critical transformation temperatures from the dilation curves. A modified Johnson–Mehl–Avrami–Kolmogorov (JMAK) analysis (used for non-isothermal conditions) was carried out to find the time exponent (n’) values controlling the rate of transformation at different cooling rates. The nature of transformed ferrite was observed to change from polygonal to acicular type, and its grain size was found to decrease with an increase in cooling rate. EBSD analysis also revealed the cooling rate to have a profound effect on the microtexture evolution of the concerned alloy. The “\(\gamma\)” fibre and rotated cube components are replaced by the transformed copper (“\(\alpha\)” fibre) components owing to faster transformation and lack of recrystallization of transformed \(\alpha \) with increase in cooling rate. Finally, a power law and logarithmic relationship of grain size and microhardness with the applied cooling rate were established.

The Effect of Size Distribution on the Geochemistry and Mineralogy of Tropical River Sediments and Its Implications regarding Chemical Weathering and Fractionation of Alkali Elements

Abstract The mineralogical and geochemical compositions of the sediments deposited by rivers have been used extensively to evaluate past chemical weathering and the physical erosion history of drainage basins at different time scales. However, the role of sediment sorting in the mineralogical and geochemical compositions of river sediment needs to be better constrained because it could significantly modify proxies used to evaluate weathering intensity in the past. In this study, major and trace element concentrations and mineralogical compositions were determined on seven different grain-size fractions of riverbed samples taken from the Pahang and Kelantan Rivers in the Malay Peninsula. The main aims are to assess chemical weathering and the fractionation of alkali elements during sediment transportation under tropical climate conditions. Fine sediments (from <2 μm to 4-8 μm) were characterized by higher concentrations of Al2O3, P2O5, V, Sc, and Cs than coarse sediments (from 8-16 μm to 32-63 μm). The presence of heavy minerals, such as zircon and monazite, was found to have critical effects on the concentration of several elements (e.g., Zr and Th), leading to extremely high elemental concentrations in the coarse-sediment fractions. Variations in elemental concentrations with particle sizes are mainly attributed to changes in the mineralogical composition during mineral sorting and weathering. In both rivers, the intensity of chemical weathering increased with decreasing grain sizes. However, the relationship between grain size and chemical weathering trends in the Pahang and Kelantan River basins was different in each case due to differences in plagioclase and K-feldspar concentrations, especially in the coarse-sediment fractions (16-32 μm and 32-63 μm). Kaolinite percentage, illite chemistry index, and illite crystallinity were directly proportional to the chemical index of alteration (CIA), suggesting that these mineralogical parameters are suitable proxies for determining chemical weathering intensity in sediments that have undergone significant changes due to mineral sorting during transportation. The comparison of Rb/K and Cs/K ratios and the CIA suggested that K and Rb mainly derive from primary minerals during the process of chemical weathering, whereas Cs is mainly present in fine weathered particles due to the reabsorption of Cs on clay minerals. Overall, our results highlight the relationship of grain size and mineral assemblages to different states of chemical weathering (and alkali fractionation) in tropical river basin sediments. These relationships need to be considered when using mineralogical and geochemical compositions to reconstruct weathering history in a “source to sink” approach.

The Relationship of Grain Size to Nickel Grade at Saprolite Zone of Lateritic Nickel Deposite in Moronopo Site, East Halmahera Regency, North Maluku

The research was conducted at the Dinding A and Dinding B, Moronopo Site PT Antam Tbk, East Halmahera, North Maluku which is a block that has been opened for the mining process. Generally the stratigraphy of laterite nickel deposits, from top (young) to bottom (old) consists of overburden, limonite, saprolite and bedrock. The saprolite zone is an economical ore layer for Ni content. This research aims to determine the relationship between grain size of ore and the mineralogy and economical Ni content. The research methods used include the grain size fractionation method with sizes of -5 cm, +5 cm, +10 cm, +15 cm, +20 cm and +25 cm, and XRF analysis to determine the Ni content. The result of this study shows the rocks in the saprolite zone containing minerals such as olivine, serpentine, garnierite and chrysoprase. The XRF analysis result shows the highest Ni content is found in the finest grain fraction (-5 cm) i.e. 2.4% and the lowest Ni content found in the coarsest grain fraction (+25 cm) i.e. 1.87 % but is still classified as economic.

Chromitite layers indicate the existence of large, long-lived, and entirely molten magma chambers

The classical paradigm of the ‘big magma tank’ chambers in which the melt differentiates, is replenished, and occasionally feeds the overlying volcanos has recently been challenged on various grounds. An alternative school of thought is that such large, long-lived and largely molten magma chambers are transient to non-existent in Earth’s history. Our study of stratiform chromitites in the Bushveld Complex—the largest magmatic body in the Earth’s continental crust—tells, however, a different story. Several chromitites in this complex occur as layers up to 2 m in thickness and more than 400 kms in lateral extent, implying that chromitite-forming events were chamber-wide phenomena. Field relations and microtextural data, specifically the relationship of 3D coordination number, porosity and grain size, indicate that the chromitites grew as a 3D framework of touching chromite grains directly at the chamber floor from a basaltic melt saturated in chromite only. Mass-balance estimates imply that a few km thick column of this melt is required to form each of these chromitite layers. Therefore, an enormous volume of melt appears to have been involved in the generation of all the Bushveld chromitite layers, with half of this melt being expelled from the magma chamber. We suggest that the existence of thick and laterally extensive chromitite layers in the Bushveld and other layered intrusions supports the classical paradigm of big, albeit rare, ‘magma tank’ chambers.

Optimal sediment grain size and sorting for survival and growth of juvenile Manila clams, Venerupis philippinarum

The characteristics of the sedimentary environment are considered significant for increasing the aquaculture production of Manila clams, Venerupis philippinarum. Among these, the grain size and sorting of the sediment, which determine the amount of pore-water-dissolved oxygen and organic matter content, can affect the growth and survival of clams. To determine the optimal grain size and sediment sorting in relation to the conditions of Manila clams (e.g., survival, growth, burrowing behavior, and condition index), we conducted three experiments. First, juvenile clams were incubated in four different grain sizes (coarse sand, 0.335–710 mm; medium sand, 0.180–0.335 mm; fine sand, 0.090–0.180 mm; and very fine sediment, < 0.09 mm). Survival was significantly higher in medium sand than in very fine sediment. The condition index of the Manila clams was higher in the medium sand than in the coarse and very fine sediments. However, the sediment grain size did not influence the shell growth or clam emergence behavior. Second, juvenile clams were incubated in three different treatments of sediment sorting (well-sorted sediment: 0.58 mm; moderately-sorted sediment: 0.46 mm; and poorly-sorted sediment: 0.37 mm). The shell growth rate was significantly higher in the poorly-sorted sediment than in any other treatment, while sediment sorting did not influence the survivorship, condition index, or emergence behavior. Third, juvenile Manila clams were incubated for 30 days in the sediment taken from two locations on the clam culturing mudflat, where a structure was installed to facilitate the settling of clam larvae (which was more poorly-sorted) or without a structure (the control). Although the survival and emergence behavior were not significantly different between the two treatments, the shell growth rate in the sediment under the structure was higher than that in the sediment with no structure. Moreover, the condition index of the Manila clams in the sediment under the structure was significantly higher than that under no structure. The results suggest that poorly-sorted sediment with an average grain size of medium sand is optimal for the survival and growth of Manila clams.

Relationship of Grain Size, Texture Distribution, and Mechanical Properties of 25Mn Casting Flange Blank Subjected to Hot Ring Rolling

The hot ring rolling of centrifugal casting 25Mn flange blank was conducted for achieving the grain and texture distribution in the whole thickness. Compared to the casting one, the mechanical properties of the hot-rolled flange are improved, and the tensile and impact fracture are dominated by the mixture of quasi-cleavage and ductile fractures. The homogeneous grain distribution with 30–38 μm in diameter is presented near the outer and inner layers, and the irregular grain is observed in the center-layer closely related to the lower recrystallization degree. The finer and uniform distribution grains with low-angle grain boundaries approximately 60% are found in the surface layers, which are caused by the HRR, resulting in the generation of many sub-grains. The misorientation changes within grains in the surface layers illustrate an increment in the refined grains. The textures are characterized by the Brass-R {111} component along //ND, Goss {110} , and Copper {112} components, which result in the excellent tensile and yield strengths but a relative low plasticity and toughness. Thus, it is feasible to fabricate 25Mn flange with sound microstructure and excellent mechanical properties hot-rolled directly from a centrifugal casting blank by controlling texture component along RD.

Electronic excitation induced modifications in surface morphological, optical and physico-chemical properties of ALD grown nanocrystalline Al2O3 thin films

Abstract In this present communication, we report the possible outcomes on the investigation of structural, optical and morphological properties of unirradiated and swift heavy ions irradiated Al2O3 thin films (120 nm) grown on silicon and glass substrate using atomic layer deposition (ALD) technique. Al2O3 thin films were irradiated using 120 MeV S9+ swift heavy ions (SHI) with a range of fluence 5E11 to 1E13 ion/cm2. The surface characteristics and increase in grain size (38–45 nm) in relation to pre and post high energy ions irradiation were examined by atomic force microscope (AFM). A quantitative detailed analysis of surface roughness along with vertical and lateral directions and surface morphology is provided by power spectral density (PSD). Moreover, the crystallite size (12–49 nm) of the unirradiated and irradiated samples was determined using the Debye Scherrer's method. It was observed that δ-Al2O3 tetragonal phase vanished after SHI irradiation. For a better understanding of the influence of high energy ion irradiation on structural properties, various parameters such as stress, strain, dislocation density and preferred orientation to be textured along the (953) plane using texture coefficient were determined by X–Ray Diffraction (XRD). The absorption coefficient was used to determine the variation in optical band gap (Eg) and Urbach energy (Eu) with the range of ion fluence. Photoluminescence (PL) spectroscopy at room temperature was carried out to understand the mechanism of significant variation in intensity and peak shifting of strong and broad photoluminescence emission spectra recorded at 250 nm and 240 nm excitation wavelengths. Further, the survey spectrum and chemical binding energy (B.E) of Al 2p and O 1s core levels at 74.2 eV and 553.45 eV in aluminium oxide unirradiated and irradiated thin films were provided by X-ray photoelectron spectroscopy (XPS) analysis. To estimate the quantitative elemental composition (2:3), the crystalline quality of the samples and thickness (120 nm), Rutherford Backscattering Spectrometry (RBS) spectra were recorded using the backscattering of high energy He2+ ions.

Monte Carlo Simulations of Topological Properties in Two-Phase Polycrystalline Materials for Several Diffusion Mechanism

Numerical simulations by means of the Monte Carlo Potts model have been provided to simulate grain structures in two-phase polycrystalline materials. The topological features in the simulated microstructure analyzed for different diffusion mechanisms over a broad range of volume fractions for both phases. The topological properties include the average number of sides, grain topology distribution and the topological size relation function. It is found that the average number of sides depends proportionally on the volume fraction. It increases as the volumes fraction increases and vice versa. Moreover, it is shown that the grain topology distribution in the self-similar growth regime can be described by time unchanged function of the relative grain size. Additionally, topological size function in the simulated microstructure can be evaluated by a quadratic function.

Ultra-precision grinding of AlON ceramics: Surface finish and mechanisms

Aluminum oxynitride (AlON) can be effectively finished by ultra-precision grinding. In this work, the ultra-precision grinding experiment was conducted on AlON to investigate surface characteristics and material removal mechanism. The ground surface has an unusual non-uniform morphology resulted from the different material removal modes. Grazing incidence X-ray diffraction (GIXRD), nanoindentation and Electron Back-Scattered Diffraction (EBSD) were carried out to study the micro-properties of AlON. The results revealed that the micro mechanical properties vary with the grain orientation on the surface. The morphologies of ground surface are consistent in the twinned grains and change with the grain orientation. By comparing the relationship of machining size and grain size, the material removal modes of individual grains should be taken into consideration during ultra-precision grinding. Based on this, a simple theoretical model was proposed to explain the material removal mechanism of AlON under ultra-precision grinding.

Timescales of collisional metamorphism from Sm-Nd, Lu-Hf and U-Pb thermochronology: A case from the Proterozoic Putumayo Orogen of Amazonia

The construction of mountain belts by continent-continent collision is a fundamental phase of the supercontinent cycle and an inevitable consequence of subduction-driven plate tectonics on Earth. Yet, quantitative estimation of the rate and duration of prograde orogenic metamorphism in high-grade collisional belts has proven elusive to constrain. Differences in the chemical partitioning and diffusive behavior of elements associated with the 147Sm-143Nd and 176Lu-176Hf isotopic systems in metamorphic garnet can provide valuable insights on the time scales over which this mineral grows and cools in regionally metamorphosed terranes. Here, we present new Sm-Nd and Lu-Hf isotopic results from multiple garnet and whole-rock aliquots from a granulite-grade metasedimentary rock from the Proterozoic Putumayo Orogen of South America. Using a combination of internal isochron dating by these two decay systems, combined with apatite U-Pb dating and pressure-temperature-time (P-T-t) constraints from mineral equilibria and chemical diffusion geospeedometry, we provide first-order insights into the time scales of a Proterozoic continent-continent collisional metamorphic event in Amazonia associated with its incorporation to the Supercontinent Rodinia. Our results indicate that these metasediments attained peak granulite-grade metamorphic conditions of nearly 0.62 GPa and 680 °C at approximately 1035 Ma, and started to cool slowly, presumably during exhumation, at a rate of ∼5 K/Myr. Simple diffusion scaling relationships and numerical modeling of Sm-Nd and Lu-Hf in garnet indicate that, while Sm and Nd were both fully re-equilibrated at peak temperatures and therefore date cooling, Lu and Hf underwent diffusive decoupling due to incomplete Hf re-equilibration. By modeling the impact of this differential re-equilibration in the development of the Sm-Nd and Lu-Hf isochrons, we constraint the duration of the prograde metamorphic path and argue that garnet growth in this sample took place over millions of years—approximately 25 Myr according to our preferred interpretation. The determined apatite U-Pb date vs. grain-size relationship cannot be reconciled with the thermal history described above when modeled using the existing experimental diffusion data, and instead suggest that much slower Pb diffusivities in this mineral compared to those predicted by the existing experimental data may have inhibited its resetting. We note that the inferred temperature-time history for the metamorphic loop of this segment of the Putumayo basement is comparable to that proposed for the metamorphism and exhumation of metasediments in the India-Asia collision zone, suggesting that similar tectonic processes and rates likely operated during the Mesoproterozoic Putumayo orogeny.

Morfometría y morfología de estomas y de polen como indicadores indirectos de poliploidía en especies del género Polylepis (Rosaceae) en Ecuador

Polylepis forests (Family: Rosaceae) are originated in the Andes and are considered one of the most threatened forest ecosystems. Throughout their evolutionary history, they have shown several episodes of polyploidy affecting their process of speciation. Cellular structures such as pollen and guard cells are highly influenced by the number of genes in each species, representing an indirect method to determine the degree of ploidy. In this study, the relationship of pollen grain size and the length of the guard cells were analyzed with genome size and chromosome number, in addition to the pollen viability of Polylepis incana, P. pauta, P. microphylla, P. racemosa y P. sericea collected from the Andean highlands of Ecuador. Stomata and pollen grains were photographed at 400X magnification and their length was measured in micrometers using ImageJ program 1.49v. Staining technique was used to determine the viability of the pollen. The results show a positive correlation that varies from R2=0.32 a R2=0.65 between the variables used depending of the species; therefore, it serves as an indirect analysis method for polyploidy. These data are important for the management and conservation of Polylepis in Ecuador, allowing prior identification of potential hybrid individuals and cytotypes along the Ecuadorian Andes in a quick and inexpensive fashion. Additionally, it opens the possibility of use this data in studies of climate change, as well as the determination of parental in reforestation and restoration projects.https://doi.org/10.25260/EA.18.28.1.1.528

Ecological risk assessment of selected heavy metals in the surface sediments of three estuaries in the southeastern coast of India

Distribution and ecological risk assessment of heavy metals in surface sediments of Vellar, Coleroon and Tirumalairajan estuaries were investigated. Fifteen sediment samples from five locations in each estuary were collected during March 2010, and organic matter, grain size and metal contents (Al, Fe, Mn, Zn, Cu and Pb) were characterized. Mean metal levels in three estuaries were followed in a descending order as Al > Fe > Zn > Mn > Cu > Pb (Vellar and Coleroon) and as Al > Fe > Zn > Cu > Mn > Pb in Tirumalairajan estuary sediments. Concentration pattern revealed that the mean values of Vellar estuary are enriched with Al (20,528 μg/g), Fe (16,368 μg/g), Zn (102.7 μg/g), Mn (63.5 μg/g), Cu (47.6 μg/g) and Pb (7.9 μg/g). Coleroon and Tirumalairajan surface sediments concentration suggested Al (4813 μg/g), Fe (2734 μg/g), Zn (47.6 μg/g), Mn (34.2 μg/g), Cu (23 μg/g) and Pb (9.2 μg/g) and Al (5348 μg/g), Fe (2257 μg/g), Zn (36 μg/g), Cu (23.5 μg/g), Mn (21.9 μg/g) and Pb (3.7 μg/g), respectively. Correlation analysis and two-way joining cluster analysis clearly exhibited the good relationship of grain size and organic matter with metals. Geo-accumulation index (Igeo) revealed that the values of Zn (2) and Cu (1) were slightly higher in Vellar estuary when compared to the other two estuaries. The enrichment factor (EF) and pollution load index values showed that the Vellar estuary was more contaminated by Zn, Pb and Cu than the Coleroon and Tirumalairajan estuaries. This study suggested that heavy metal input to the Vellar estuary should be regulated in the near future, particularly with regard to Zn, Cu and Pb on the basis of threshold effect level and effects range low benchmarks when compared to the other two estuaries. Comparative results with three estuaries suggested anthropogenic input rather than a natural process as a contamination source. This study will help in developing the effective strategies of pollution control and sediment remediation of the estuarine and marine environments.

Evaluation of dynamic recrystallization behaviors in hot-extruded AA5083 through hot torsion tests

Hot torsion tests were carried out to evaluate the dynamic recrystallization (DRX) behaviors of hot-extruded AA5083 at various deformation conditions. Flow curves showed the peak followed by the flow softening to the steady-state or to the failure strain, indicating that the DRX occurred during deformation. The peak stress increased as the temperature decreased and the strain rate increased. Constitutive relationship and Zener-Hollomon (Z) parameter were used to evaluate the DRX characteristics. Peak and steady-state stresses were generalized by the dimensionless parameter, Z/A, to reveal the DRX mechanism. The empirical relationship of the DRXed grain size with the deformation conditions was established, and decreased with increasing Z parameter. The relationship for the fraction of DRXed grains was established as a function of the effective strain at given deformation conditions from the experimental data. The Avrami relationship based on micro-hardness measurement was used to describe the DRX kinetics, and was fitted well with the observed DRX fraction.

Effects of Y doping ions on microstructure, dielectric response, and electrical properties of Ca1−3x/2Y x Cu3Ti4O12 ceramics

The effects of Y3+ doping ions on ceramic microstructure, dielectric response, and electrical properties of Ca1−3x/2Y x Cu3Ti4O12 (x = 0, 0.05, 0.10, and 0.15) ceramics prepared by a modified sol–gel method were investigated. A grain size of Ca1−3x/2Y x Cu3Ti4O12 was reduced by Y3+ ions due to a solute drag effect. Substitution of CaCu3Ti4O12 ceramics with suitable Y3+ concentration of 5 at. % can improve dielectric properties with high-dielectric permittivity of e′ ~ 1.37 × 104 and low tanδ ~ 0.05 at 1 kHz. The results revealed that the relationship of the mean grain size and e′ cannot be formulated. Using impedance spectroscopy analysis, the grain boundary resistance (R gb) of Ca1−3x/2Y x Cu3Ti4O12 ceramics was found to be strongly enhanced by Y3+ doping ions with x = 0.05. With further increasing x from 0.05 to 0.15, R gb decreased. While the grain resistance tended to increase with increasing Y3+ concentration (x = 0–0.15). Variation of a low-frequency tanδ value in all Ca1−3x/2Y x Cu3Ti4O12 ceramics due to the influence of Y3+ substitution was well consistent with their changes in R gb values. Non-Ohmic properties of Ca1−3x/2Y x Cu3Ti4O12 ceramics were also investigated.

413 AZ31合金の強度に及ぼす結晶粒径の影響(OS4-(3),OS4 オーガナイズドセッション≪材料・組織と加工≫)

In recent years, high-strength and light-weight materials are required to reduce fuel consumption while retaining sufficient strength for automobiles, airplanes, etc. Magnesium-based alloys are attractive because they have low density and high specific strength. But they have a limitation in practical use due to lower ductility and strength than aluminum-based alloys. It is well-known that strength of magnesium alloys can be improved effectively by reduction of grain size in relation to their hexagonal close-packed structure. In this study, the influence of the grain size on mechanical properties of AZ31 alloys is studied and strengthening mechanism is discussed.

Relationship of grain size and deformation mechanism to the fracture behavior in high strength–high ductility nanostructured austenitic stainless steel

In this study we underscore the dependence of grain structure and deformation mechanism on the fracture behavior in a high strength–high ductility bearing nanograined/ultrafine-grained austenite stainless steel. In high strength nanograined steel, deformation twinning contributed to excellent ductility, while in the low strength coarse-grained steel, the high ductility is attained as a consequence of strain-induced martensite transformation. Interestingly, the differences in deformation mechanism of steels deformation mechanisms of steels with different grain structures but with similar elongations influenced the mode of fracture, a behavior that is governed by the change in austenite stability with grain size. The areal density of voids and their average diameter in the fracture surface also increased with increasing grain size, which ranged from 320nm to 22μm.

Grain-Size Components As Markers of Origin and Depositional Processes In the Coastal Zone of the Golfe Du Lion (Mediterranean Sea, France)

Abstract A study of beach and nearshore sands between the mouth of the River Aude and Cap d'Agde (northwestern Mediterranean Sea) shows the existence of four sediment types (ST): ST1 to ST4, with ST2 seemingly deriving from ST1, revealed by grain-size modal analysis and confirmed by a deconvolution program (LogNormal Deconvolution of Grain Size). Grain-size skewness is related to a much more persistent multimodality than graphic evidence can show. Multimodality results from mixtures of generally three STs and/or variants (the latter defining monotype grain-size distributions). Monotype mixtures are unequally distributed in morphodynamic zones, very abundant on the lower shoreface, significantly present on the berm and inner bar, but rare in the most dynamic zones (i.e., the collision zone and outer bar). On the berm and lower shoreface, modal values of the three sedimentary variants retain a close grain-size relationship. On the berm, where only bedload is present in the swash, monotype grain-size distribution trends towards a lognormal model. This trend can also be observed on the lower shoreface, where there are numerous monotype grain-size distributions (GSDs), possibly indicating a dominant process. When compared with ST1-dominated grain-size distributions of the outer bar zone, the distribution of the derived ST2 on the lower shoreface has an added fine tail derived from the coarse-skewed outer-bar sands. In addition, positive skewness of the lower-shoreface sands could indicate input of fine particles from deeper zones under the influence of shoaling waves and upwelling. Morphodynamic zones are approximately characterized by the distribution of grain-size indices. A change in the direction of the skewness sign can be observed between the shoaling zone and more energetic zones, from the breaker zone up to the berm. Finally, a more detailed description of the spatial properties of grain-size distributions could, first, help explore possible mechanisms underlying sediment sorting in the coastal zone and, second, provide a set of indices that would be of use in paleogeographic reconstructions and organization of basin borders, while improving discrimination and classification of environments.