Fine-grained Samples Research Articles

Characterization of deformation-induced martensite with various AGSs upon Charpy impact loading and correlation with transformation mechanisms

Deformation-induced martensitic transformation (DIMT) during quasi-static loading has drawn much attention in recent years since it is considered as one of the key strengthening mechanisms in advanced high-strength steels (AHSS). However, systematic investigations on martensitic transformation at high strain-rates are scarce due to difficulties in experimental designs. In this contribution, interrupted Charpy tests were used to study the transformation sequence of DIMT under high strain-rates (~10 2 –10 3 s −1 ). Austenitic 321 stainless steel samples with increasing austenite grain sizes (AGSs) were designed to demonstrate the change in transformation sequence of α'-martensite and its morphology. Quasi-in-situ electron backscattered diffraction (EBSD) and selected transmission electron microscopy (TEM) experiments have revealed that, as the AGSs increases, the nucleation sites of α'-martensite change from austenite grain boundaries in ultra-fine-grained (UFG) samples to additional twin boundaries in fine-grained (FG) samples, and finally to ε-martensite in coarse-grained (CG) samples. Due to the spatial constraints imposed by different crystallographic boundaries, the morphology of transformed α'-martensite shifts from blocky in UFG samples to film-like in CG samples, with FG samples having a mixed morphology. It is found that the changed transformation sequence can be understood by considering the combined effect of stacking fault energy and twinning nucleation stress of austenite. • Quasi-in-situ observation of DIMT under dynamic loading conditions. • TRIP (ε + α'), TWIP+TRIP (α'), and TRIP (α') occurred with decreasing austenite grain sizes. • The morphology of DIM is controlled by intermediate deformation products. • The absence of twins and ε-martensite resulted in blocky α'-martensite in UFG steels. • High SFE and twinning nucleation stress suppressed the formation of ε-martensite and twins.

Effects of pressure on diffusion creep in wet olivine aggregates

We report the results of an experimental study to determine the influence of pressure on diffusion creep in wet olivine. In order to observe diffusion creep at high-pressure conditions at laboratory strain rates, we prepared ultra-fine grained (0.22–0.72 μm) olivine aggregates both from San Carlos olivine and from oxide mixtures using a solgel technique. All samples contain some water (~1000 ppm wt) presumably due to adsorption on fine-grained powder samples. We used Deformation-DIA (D-DIA) coupled with synchrotron X-ray facility (6-BM-B beamline at APS) to perform in-situ high pressure (3–10 GPa) deformation experiments in the temperature range 973–1123 K. The operation of diffusion creep in our samples was inferred from the weak (hkl) dependence of lattice strain, the much smaller strength of our samples compared to the strength expected for dislocation creep, and the estimate of stress exponent. Diffusion creep was also confirmed from a comparison to previous results on diffusion creep at lower pressures. We assume the flow low of the following form ε˙∝CWrd−mexp−PV∗RT (ε̇: strain rate, CW: water content, d: grain size) with r = 0.7–1.0 and m = 2 or 3, from which we obtain the activation volume (V*) of 2.5 +/− 0.6 cm3/mol. This activation volume is substantially smaller than that for dislocation creep implying that diffusion creep plays an important role in the deep upper mantle. Some implications for seismic anisotropy are also discussed.

Triassic tungsten mineralization in Nanling metallogenic belt: A case study of the Zanshi tungsten deposit in the Yajiangqiao area, eastern Hunan Province, China

The Nanling metallogenic belt is rich in critical metal minerals, e.g., tungsten, tin, and rare earth element (REE). The newly discovered Zanshi tungsten deposit, located at the northeastern part of the Nanling metallogenic belt, has drawn great attention from geologists for its rare Triassic magmatic-hydrothermal event in this region. Based on detailed field work, a series of geochemical and geochronological analyses, including whole-rock geochemical analyses consisting of major and trace elements, LA-ICP-MS monazite U-Pb dating of the granites and quartz Rb-Sr and muscovite 40Ar-39Ar isotopic dating of the ore-bearing quartz veins, were carried out in this study, aiming to constrain the rock- and ore-forming ages of the deposit as well as the petrogenesis of granites. The whole-rock geochemical analyses, the medium to fine-grained two-mica monzonitic granites in the Zanshi tungsten deposit are peraluminous S-type granites and derived from the partial melting of metamorphic graywackes in a post-collisional extensional tectonic setting. The LA-ICP-MS monazite U-Pb dating on the two medium- to fine-grained two-mica monzonitic granite samples yields weighted average ages of 218.2 ± 1.2 Ma (MSWD = 1.3) and 221.7 ± 1.7 Ma (MSWD = 2.7), respectively. These ages are consistent with the quartz Rb-Sr and muscovite 40Ar-39Ar isotopic ages of the ore-bearing quartz veins, which are 218.7 ± 3.2 Ma and 215.1 ± 2.0 Ma, respectively, revealing that the tungsten mineralization in this deposit is related to the Triassic magmatic-hydrothermal activity. Combined with previous studies, the Zanshi tungsten deposit likely experienced about 5 M.y. of magmatic evolution and 3.6 M.y. of mineralization. Meanwhile, the cooling rate of the ore-forming fluids of this deposit was about 111 °C/M.y., which may be regarded as a controlling factor which affects the ore grade of the deposit.

Application of in situ U-Pb carbonate geochronology to Stenian-Tonian successions of North China

Linking geological and biological events requires a robust geochronologic framework, which is especially challenging for poorly fossiliferous Precambrian strata. Although this can be achieved through zircon U-Pb dating, only maximum or minimum ages can typically be obtained, with rare interbedded volcanic ash beds providing precise depositional ages. U-Pb dating of authigenic carbonates could potentially become a more widely applicable geochronometer, but only if carbonate minerals can be dated with sufficient precision. A renaissance in carbonate U-Pb geochronology, utilizing the in situ laser ablation method, has opened new doors in the application of this method to geological problems. Here we apply laser ablation U-Pb dating to carbonate-rich sedimentary strata of likely Meso-Neoproterozoic age on the southeastern margin of the North China Craton, resulting in two meaningful U-Pb ages of 1036 ± 45 Ma and 1010 ± 36 Ma (2σ), from early diagenetic fine-grained microspar samples. As well as being mutually consistent, these new ages show that precision approaching the limiting uncertainty of the reference material used (∼2.5% 2σ) can be achieved. Success in this study holds promise for dating other key Precambrian successions.

Geochemistry and petrogenesis of alkaline rear-arc magmatism in NW Iran

High Na- to K- alkaline magmatism is common in the rear-arc region of the Cenozoic Urumieh-Dokhtar Magmatic Belt of Iran, but their geochemical signatures, as well as their formation mechanisms, have been poorly studied thus far. In the Kleybar area of NW Iran, Middle Eocene magmatic activity comprises silica-undersaturated to -saturated gabbros, monzogabbros, monzosyenites to nepheline-monzosyenites, and nepheline syenite as well as tephritic to trachy-basaltic and trachy-andesitic dikes. New 40Ar39Ar results show a restricted age range (39.2–43.6 Ma) for the intrusive rocks (43.16 ± 0.43 and 43.34 ± 0.43 Ma for gabbros, 43.56 ± 0.44 for monzogabbros, 39.22 ± 0.48 and 42.09 ± 0.42 Ma for nepheline syenites, 42.17 ± 0.42 Ma for nepheline-monzosyenites), whereas a cross-cutting trachy-andesitic dike yielded an 40Ar39Ar age of 41.78 ± 0.42 Ma. The Kleybar rocks are enriched in alkalis (K2O and Na2O) with variable K2O/Na2O ratios (0.14 to 2.93), light rare earth elements and large ion lithophile elements such as Th, Rb, K, U and Pb. High field strength elements such as NbTa are depleted in these rocks.The isotopic compositions of the different rock types are quite variable: gabbros and monzogabbros have 87Sr/86Sr(t) = 0.70419–0.70436, εNd(t) = +3.1 to +3.8 and εHf(t) = + 7.8 to +10.1; nepheline monzosyenites and nepheline syenites have 87Sr/86Sr(t) = 0.70359–0.70566 (except a nepheline syenite with a ratio of 0.74833 and very high Rb/Sr), εNd(t) = +1.5 to +4.2 and εHf(t) = +4.6 to +8.8; and trachy-basaltic to trachy-andesitic to tephritic dikes have 87Sr/86Sr(t) = 0.70437–0.70469, εNd(t) = +2.8 to +4.2 and εHf(t) = +8.3 to +10. In the thorogenic-Pb isotope diagram, the Kleyber igneous rocks define an array above the Northern Hemisphere Reference Line (NHRL), with ∆8/4 (deviation from the NHRL) of ~40–60. These samples also plot above the NHRL in uranogenic Pb space (∆7/4–5-10). The positive ∆8/4 Pb and ∆7/4 Pb may reflect the involvement of subducted terrigenous sediments in their mantle source during the subduction of the Neotethyan oceanic lithosphere. Two nepheline syenite samples have significantly higher thorogenic and uranogenic Pb isotopic compositions, that may reflect assimilation of surrounding clay-rich sedimentary rocks.Modelling of trace elements compositions using less fractionated Kleybar trachybasalt and fine-grained monzogabbro samples indicate that a 96:4 mixture of the depleted mantle and subducting (trench)-sediment melts with 6% aggregated fractional melting closely matches the trace-element abundances of the Kleybar trachybasalt and monzogabbro. Together with previous studies on high-K volcanic rocks from NW Iran, our results indicate that Neotethyan slab retreat and related extension of the Iranian continental lithosphere in the rear-arc region of the Urumieh-Dokhtar Magmatic Belt generated alkali-rich magmatic rocks throughout the NW Iran rear-arc during Middle-Late Eocene.

Исследование особенностей высокотемпературной деформации керамик из чистого карбида вольфрама с различным размером зерна

The mechanism of high-temperature creep deformation during compression tests of binderless tungsten carbide specimens with different initial particle size was studied. Tungsten carbide samples with high relative density (96.1 – 99.2 %) were obtained by high-speed spark plasma sintering (SPS) from nano-, submicron-, and micron-sized α-WC powders. The creep tests were carried out in two modes: isothermal soaking at different temperatures (1300 – 1375 °C) at a given stress, allowing to estimate the activation energy of creep, and tests by “stress jumps” at 1325 °C, allowing to estimate the value of the coefficient n in the creep equation. It is shown that the value of creep activation energy in ultrafine grained tungsten carbide with grain size ~ 0.15 µm sintered from plasma chemical nanopowders is ~ 31 kTm. This value is 1.5 – 2 times higher than the creep activation energy in fine-grained tungsten carbide samples obtained by SPS from submicron (~ 0.8 μm) and micron (~ 3 μm) industrial powders. It was found that the value of the coefficient n varies from 2.4 to 3.1, which corresponds to the case of motion of lattice dislocations in the field of uniformly located point obstacles. It has been suggested that one of the reasons for the increase in creep activation energy in tests of tungsten carbide is an increased volume fraction of W2C low carbide particles formed during high-speed sintering of plasma-chemical α-WC nanopowders with an increased concentration of adsorbed oxygen.

Hierarchical Multilabel Ship Classification in Remote Sensing Images Using Label Relation Graphs

Hierarchical multilabel classification (HMC) assigns multiple labels to each instance with the labels organized under hierarchical relations. In ship classification in remote sensing images, depending on the expert knowledge and image quality, the same type of ships in different remote sensing images may be annotated with different class labels from coarse to fine levels such as merchant ship (MS) or container ship (CTS). In this article, we propose a novel deep network with two output channels and their associated loss functions to learn an HMC classifier using samples labeled at different levels in the hierarchy. In the proposed network, a hierarchy and exclusion (HEX) graph is introduced to model the label hierarchy, which satisfies hierarchical constraints by encoding semantic relations between any two labels. The output nodes of the first channel are organized according to the HEX graph, and its corresponding probabilistic classification loss is built to reflect the hierarchical structure of the HEX graph. On the other hand, the output nodes of the second channel only represent the finest grained (last level in the hierarchy) classes, and its multiclass cross-entropy loss is designed to enhance the discriminative power of the HMC classifier on the last level labels, which is also compatible with constraints in the HEX graph. The combination of these two losses from two output channels can effectively transfer the hierarchical information of ship taxonomy during network training. Experimental results on two commonly used ship datasets demonstrate that the proposed method outperforms the state-of-the-art HMC approaches, and is especially advantageous when trained with fewer fine-grained samples.

X-Ray CT Investigation on Fractal Characteristics of Fine-Grained Tailing Sand in Fujian’s Makeng: Insight into the Mesoscopic Seepage Failure

This work is aimed at revealing the mesophysical process and mechanical behaviors of fine-grained tailing sand during seepage failure. The macroscopic seepage tests combined with posttest X-ray computed tomography (CT) were employed to study the fractal characteristics of mesostructure. Results show that before and after the seepage failure of fine-grained tailing sand, fractal of pore distribution ( D pd ) and fractal dimension of pore size ( D ps ) show a relatively obvious positive correlation with porosity. Tailing particles migrate along the seepage direction during the seepage process, resulting in the gradual decrease of D pd and pore distribution area. The D ps reflects the variation characteristics of pore number distribution with different pore sizes. The increase in D ps leads to a decrease in the uniformity of pore size and an increase in the size difference between pores. The mass fractal dimension ( D m ) of fine-grained tailing sand samples ranges from 1.6472 to 1.8256. With the increase of D m , the coefficient of uniformity ( C u ) of tailing sand tends to increase. The D m method can discern the seepage failure type of fine-grained tailing sand, and it is more accurate than the traditional method. This study provides a reference for the prevention and control of the seepage failure of tailing dam.

Enhanced Adaptive Neuro-Fuzzy Inference System Using Reptile Search Algorithm for Relating Swelling Potentiality Using Index Geotechnical Properties: A Case Study at El Sherouk City, Egypt

The swelling potentiality is a vital property of fine-grained soils strictly related to the index properties and chemical composition. The integration of machine learning techniques and geotechnical parameters provided a new integrative approach for predicting the free swelling index (FSI) and the swelling pressure (SP). In this paper, an adaptive neuro-fuzzy inference system (ANFIS) using named Reptile Search Algorithm (RSA) is presented to predict the swelling potentiality for fine-grained soils in the foundation bed at El Sherouk city, Egypt. The developed predictive model, named RSA-ANFIS, used as input measured 108 natural fine-grained soil samples of index geotechnical parameters and chemical composition as input data and the measured data of the free swelling index and the swelling pressure as output data. To justify the performance of the developed model, a comparative study was carried out, and the results show that the developed RSA-ANFIS has a high performance over the competitive methods in terms of coefficient of determination, root mean square error (RMSE), and mean absolute error (MAE). This new integrative approach is considered at the highly developed stage to predict and improve the analysis of multi-parameter soil behavior and could be applied in other objective variable datasets.

Overcoming the trade-off between stretch formability and heat resistance in magnesium via alloying dilute neodymium

This work aims to provide a reliable reference and a low-cost strategy for overcoming the trade-off between stretch formability and heat resistance in Mg alloys. A dilute Mg-0.8 wt%Nd alloy sheet was prepared for this purpose, and hot compression was conducted in order to regulate the microstructure and texture. For comparison, the samples with and without hot compression were labeled as fine-grained (FG) and coarse-grained (CG) samples respectively, corresponding to the occurrence of dynamic recrystallization. Tensile creep tests were carried out at 473 K and Erichsen tests were conducted at room temperature. Both the CG and the FG samples had higher stretch formability and stronger creep resistance than commercial Mg alloys tested for comparison. Especially, the FG sample performed the best in overcoming the trade-off. Pyramidal<c+a> slip dominated the creep behavior of the FG sample and enhanced the heat resistance, avoiding the deterioration caused by cross-slip, twinning and grain boundary sliding. High Schmid factors for basal slip of the fine grains enhanced the stretch formability of the FG sample, and compensated the adverse effect of the relatively low Schmid factors of the residual coarse grains. Thus, the dilute Mg-0.8 wt%Nd alloy successfully overcame the trade-off between stretch formability and heat resistance.

Standardized Dose–Response Curve (sDRC) Construction for OSL Dating of Quartz from Bohai Coast, NE China

The optically stimulated luminescence (OSL) dating method promises to provide reliable ages for various Quaternary archives. Coastal sedimentation in the Bohai Sea (northeastern China) since the Middle Pleistocene has been influenced by paleoenvironmental and sea-level change, of which dating has been restricted using the OSL dating approach in multiple investigations. In this study, to establish a robust OSL chronological framework of the Bohai coastal sediments more effectively, the regional standardized dose–response curve (sDRC) was constructed for quartz OSL dating in the Bohai Coast (NE China) using two existing approaches. The sDRC-determined equivalent doses are broadly in agreement with those using the individual DRC for each sample. Data used for DRC construction of the fine-grained (FG) quartz samples are less scattered than those of the coarse-grained (CG) quartz samples, probably due to the signal-averaging effect for the FG samples, while the OSL signal of the CG quartz samples might document provenance information that yield relatively scattered distribution. The two approaches used in this study yield identical sDRCs, indicating that both the methods are applicable for sDRC construction in the Bohai Sea.

Reducing surface roughening in microscale laser dynamic flexible bulging by using laser pre-shocking

Roughening of the free surface in micro-forming results in the local necking and subsequent fracture, which seriously affects the formability of sheet metals. In this work, laser pre-shocking (LPS) was introduced into microscale laser dynamic flexible bulging (μLDFB) to reduce surface roughening in terms of reducing the surface roughness and refining the internal grains. In LPS experiments, when the laser energy is 447 mJ, the rebound of the copper foils can be negligible. LPS can be expected to suppress the surface roughening by reducing the initial roughness R0, increasing the N value and decreasing the rate of surface roughening. The copper foils subjected by 447 mJ LPS were used for the μLDFB experiments. The 50 μm T2 copper foils with four different grain sizes were used in μLDFB under different laser pulse energies. When laser pulse energy ranges from 325 mJ to 575 mJ, compared with μLDFB without LPS, the surface roughness on the bottom surface of the bulging sample is decreased. And the nano-hardness, elastic modulus and forming uniformity are significantly improved. In μLDFB experiments without LPS, for fine-grained samples, the cracks initiate in the bulging transition zone under 725 mJ laser energy due to surface roughening. As laser energy increases to 1050 mJ, the cracks initiate in the mold entrance zone due to the strong stress concentration. For coarse-grained samples, cracks initiate under 575 mJ laser energy, and the propagations of the cracks are difficult to predict due to non-uniform distribution of grain size and the difference of grain orientation. The experimental results suggest that LPS can reduce the possibility of the premature fracture caused by the local necking, and alleviate the uncertainty in the fracture mode.

Synthesis of Niobium-Alumina Composite Aggregates and Their Application in Coarse-Grained Refractory Ceramic-Metal Castables.

Niobium-alumina aggregate fractions with particle sizes up to 3150 µm were produced by crushing pre-synthesised fine-grained composites. Phase separation with niobium enrichment in the aggregate class 45–500 µm was revealed by XRD/Rietveld analysis. To reduce the amount of carbon-based impurities, no organic additives were used for the castable mixtures, which resulted in water demands of approximately 27 vol.% for the fine- and coarse-grained castables. As a consequence, open porosities of 18% and 30% were determined for the fine- and coarse-grained composites, respectively. Due to increased porosity, the modulus of rupture at room temperature decreased from 52 MPa for the fine-grained composite to 11 MPa for the coarse-grained one. However, even the compressive yield strength decreased from 49 MPa to 18 MPa at 1300 °C for the fine-grained to the coarse-grained composite, the latter showed still plasticity with a strain up to 5%. The electrical conductivity of fine-grained composite samples was in the range between 40 and 60 S/, which is fifteen magnitudes above the values of pure corundum.

Influences of initial microstructures on martensitic transformation and textures during cold rolling and tensile mechanical properties in high manganese TRIP steel

The deformation-induced transformation characteristics and texture evolution of α′-martensite during cold rolling together with the tensile properties of two specially prepared initial microstructures (bimodal elongated γ grains and fine equiaxed γ grains) were investigated in high manganese TRIP steels. The results showed that the thermally induced martensite was restrained effectively by refining grains or introducing crystal defects like dislocations, which provided a nearly full austenite phase for the subsequent TRIP process. Compared with the solution-treated sample containing coarse equiaxed γ grains, the fine-grained sample revealed a better plasticity and a higher strength due to grain refinement and progressive TRIP process. The bimodal elongated-grained sample exhibited the highest strength and sufficient plasticity because the dislocation strengthening exceeded the fine-grain strengthening and martensitic transformation was delayed. The transformation textures of two kinds of samples differed in that the fine-grained sample demonstrated typical {113}<110>α from the Copper-type γ texture and {332}<113>α from the Brass-type γ texture, whereas {001}<110>α texture occurred in the bimodal elongated-grained sample in addition to the above two components. In the early stage of TRIP, there was an obvious orientation dependence, and the {100}- and Copper-oriented γ grains preferentially transformed to martensite rather than γ grains with Brass orientation.

Microstructural Evolution of a 3003 Based Aluminium Alloy during the CSET Process.

A new severe plastic deformation technique, known as the complex shearing of extruded tube (CSET), was applied to a 3003 based model aluminium alloy. This technique, consisting of a combination of extrusion and two consecutive Equal Chanel Angular Pressing (ECAP) passes accompanied with concurrent torsional straining, is capable to produce a fine-grained tubular sample directly from a bulk metallic cylinder in one forming operation. In the present paper, the microstructural development of the alloy during partial processes of CSET was studied in detail using light microscopy, electron backscatter diffraction, and transmission electron microscopy. It was found that CSET technique refines the grain size down to 0.4 µm and, consequently, increases the microhardness from the initial value of 40 HV to the final value of 120 HV. The contributions of partial processes of CSET to the total strain were estimated.

Grain-size dependent elastic-plastic deformation behaviour of inconel 625 alloy studied by in-situ neutron diffraction

The effect of grain size on elastic-plastic deformation and twinning behaviour of Inconel 625 alloy was studied. Alloy samples were investigated using compressive deformation analysis, in-situ neutron diffraction, electron backscatter diffraction, and transmission electron microscopy. The alloy was found to exhibit strong elastic and plastic anisotropy. Grain refining was found to have several advantages, including the increased grain-specific diffraction elastic moduli, improved compatibility and homogeneity of polycrystalline deformation, and enhanced yield strength at room temperature. Two strong preferred orientations were present in coarse-grained samples: the Copper orientation of {112}<111>, in deformed grains because of dislocation slip, and the Brass orientation of {110}<112>, in elongated grains owing to deformation twinning. The coarse-grained samples also showed large quantities of stacking faults, multiple-slip lines, and dislocations. In contrast, stacking faults were not observed in fine-grained samples, however, a dense presence of slip lines, dislocations, and dislocation pile-ups at grain boundaries were observed. The fine-grained samples exhibited a higher density of dislocations than the coarse-grained samples given the same applied load during compressive deformation. The deformation mechanisms of the coarse-grained alloy were dominated by dislocation slipping and the formation of stacking faults, while the deformation of the fine-grained alloy showed only dislocation slipping.

Intensification of the flotation separation of potash ore using ultrasound treatment

The difficulties of beneficiation of the potash ores by flotation is controlled by the structural similarity of the soluble salt minerals such as halite NaCl and sylvite KCl leading to the same surface properties and reactivity of those minerals when cationic reagents are used as collector. In this work, the effect of sonication on the selective flotation and separation contrast between sylvite KCl and halite NaCl in saturated salt solutions was investigated. The flotation experiments were performed on the potash ore samples from the Verkhnekamskoye deposit, Russia, using primary amine as the collector. Different particle sizes (0.5–1 mm, 0.25–0.5 mm, and 0.1–0.25 mm) with similar contents of K (26–29 %) and Na (16.5–18 %) and the same mineralogical compositions were studied. Pulp sonication was performed during the conditioning and/or flotation stages at 30 % solid content in a mechanical flotation machine using an ultrasonic generator at powers from 10 to 75 W at a resonant frequency of 20 kHz. In the absence of the sonication, the maximum recovery of sylvite was obtained for the size fraction of 0.25–0.5 mm (93.99 %) while the sylvite recovery was low for the coarse-grained fraction (0.5–1 mm). The lowest flotation selectivity was observed for the fine-grained ore sample (0.1–0.25 mm). The combined ultrasonic treatment of this sample during conditioning and flotation approximately halved the recovery of NaCl in the potash concentrate (from 17.9 % to 9.9 %) and increased the KCl recovery from 89.9 % to 95.9 %. The addition of a frother increased significantly the sylvite recovery under sonication for coarse size fraction while the effect was less prononoced for the intermediate size fraction. The enhanced flotation selectivity between KCl and NaCl under sonication was attributed to the increased detachment of weak hydrophobic NaCl particles from air bubbles according to the particle size and mode of treatment. The collector desorption from the halite surface unrevealed by the diffuse reflectance infrared spectroscopy was suggested as a factor controlling the selective detachment of low hydrophobic particles under sonication. Therefore, based on our results, a balance must be established between the particle size, collector consumption, ultrasound treatment power, and sonication method (during conditioning with reagents or/and flotation) to optimize the separation between NaCl and KCl.

Distortion of a polycrystalline Al bar in a vice fixture: molecular dynamics analysis of grain movement and rotation

The deformation of a nano-sized polycrystalline Al bar under the action of vice plates is studied using molecular dynamics simulation. Two grain sizes are considered, fine-grained and coarse-grained. Deformation in the fine-grained sample is mainly caused by grain-boundary processes which induce grain displacement and rotation. Deformation in the coarse-grained sample is caused by grain-boundary processes and dislocation plasticity. The sample distortion manifests itself by the center-of-mass motion of the grains. Grain rotation is responsible for surface roughening after the loading process. While the plastic deformation is caused by the loading process, grain rearrangements under load release also contribute considerably to the final sample distortion.

Hierarchical neural reconstruction for path guiding using hybrid path and photon samples

Path guiding is a promising technique to reduce the variance of path tracing. Although existing online path guiding algorithms can eventually learn good sampling distributions given a large amount of time and samples, the speed of learning becomes a major bottleneck. In this paper, we accelerate the learning of sampling distributions by training a light-weight neural network offline to reconstruct from sparse samples. Uniquely, we design our neural network to directly operate convolutions on a sparse quadtree, which regresses a high-quality hierarchical sampling distribution. Our approach can reconstruct reasonably accurate sampling distributions faster, allowing for efficient path guiding and rendering. In contrast to the recent offline neural path guiding techniques that reconstruct low-resolution 2D images for sampling, our novel hierarchical framework enables more fine-grained directional sampling with less memory usage, effectively advancing the practicality and efficiency of neural path guiding. In addition, we take advantage of hybrid bidirectional samples including both path samples and photons, as we have found this more robust to different light transport scenarios compared to using only one type of sample as in previous work. Experiments on diverse testing scenes demonstrate that our approach often improves rendering results with better visual quality and lower errors. Our framework can also provide the proper balance of speed, memory cost, and robustness.

ВЛИЯНИЕ ПОЛИДИСПЕРСНОГО БЕТОННОГО ЛОМА 3D-ПЕЧАТИ НА СТРУКТУРООБРАЗОВАНИЕ БЕТОНА

The article considers the influence of polydisperse concrete scrap of 3D printing on the structure formation of concrete during its repeated application. It is established that the favorable effect on the strength is due to the presence of thin layers on the surface of the secondary fine aggregate in the form of hydrate phases that enhance adhesion to the forming cement matrix. At the same time, an important multifunctional role is played by a fine fraction consisting of a cement matrix with a small amount of pulverized clinker and quartz. It increases the volume of the binder part; performs the function of the centers of crystallization of hydrate phases; promotes the formation of a compact and homogeneous structure by filling the pores; increases the strength due to the hydration of the minerals alite and belite. It is shown that the minimization of the voidness of the fine-grained part of the concrete scrap is largely due to the polymodal grain composition, which contributes to the optimization of the structure of fine-grained concrete and increases the strength. The features of the microstructure of fine-grained concrete samples are established. Artificial conglomerate based on concrete scrap is characterized by a compact structure, due to the high adhesion of the fine aggregate to the cement matrix of concrete, filling the pores with hydrate phases and fine particles, in contrast to the samples of fine-grained concrete of the control composition, which structure is characterized by a weak contact zone between the aggregate and the cement matrix.