Fine Fragments Research Articles

Fragmentation Characteristics of Seafloor Massive Sulfides: A Coupled Fluid-Particle Flow Simulation

The research on the fragmentation mechanism of seabed minerals under high ambient pressure significantly contributes to the exploitation of seafloor massive sulfides (SMS). In this paper, the uniaxial compressive strength (UCS) test and triaxial compressive strength (TCS) test were carried out on two kinds of SMS samples to obtain the key mechanical properties of minerals, including cohesion, internal friction angle, compressive strength, and elastic modulus. Then, based on these mechanical parameters, the fluid-solid coupling cutting model of two SMS samples at high ambient pressure is established by using the coupling method of discrete elements and smooth particles. A mixed-bond model is selected, and the microscopic parameters are determined by a repeated calibration process. Meanwhile, the cutting force and debris information are monitored and collected in real time during the whole cutting process. The results show that under different confining pressure environments, the model shows the transformation of minerals from brittleness to ductility. The cutting force increases with the increasing ambient pressure. Due to the fluid pressure, the crushing mechanism tends to shear failure, which is more likely to produce mud and finer fragments.

Neo-sex chromosome evolution and phenotypic differentiation across an elevational gradient in horned larks (Eremophila alpestris).

Genetic structure and phenotypic variation among populations are affected by both geographic distance and environmental variation across species' distributions. Understanding the relative contributions of isolation by distance (IBD) and isolation by environment (IBE) is important for elucidating population dynamics across habitats and ecological gradients. In this study, we compared phenotypic and genetic variation among Horned Lark (Eremophila alpestris) populations from 10 sites encompassing an elevational gradient from low-elevation desert scrub in Death Valley (285a.s.l.) to high-elevation meadows in the White Mountains of the Sierra Nevada of California (greater than 3000m a.s.l.). Using a ddRAD data set of 28,474 SNPs aligned to a high-quality reference genome, we compared genetic structure with elevational, environmental, and spatial distance to quantify how different aspects of the landscape drive genomic and phenotypic differentiation in Horned Larks. We found larger-bodied birds were associated with sites that had less seasonality and higher annual precipitation, and longer spurs occurred in soils with more clay and silt content, less sand, and finer fragments. Larks have large neo-sex chromosomes, and we found that associations with elevation and environmental variation were much stronger among neo-sex chromosomes compared to autosomes. Furthermore, we found that putative chromosomal translocations, fusions, and inversions were associated with elevation and may underlie local adaptation across an elevational gradient in Horned Larks. Our results suggest that genetic variation in Horned Larks is affected more by IBD than IBE, but specific phenotypes and genomic regions-particually on neo-sex chromosomes-bear stronger associations with the environment.

Characteristics of micro-explosive dispersion of gel fuel particles ignited in a high-temperature air medium

The characteristics of processes developing during the ignition and combustion of single gel fuel particles with a mass of 10 mg in a high-temperature motionless air medium were investigated by means of a hardware and software system. The system featured a high-speed video camera, LED spotlights and a laptop with commercial and custom software. A group of fuel compositions was derived from oil-filled cryogels alone and with the addition of fine solid combustible components. Polyvinyl alcohol with 10 wt% in an aqueous solution was used as an organic polymer thickener. When exposed to rapid heating, fuel compositions (oil + aqueous solution of PVA + emulsifier; oil + coal dust + aqueous solution of PVA + emulsifier) were characterized by the micro-explosive dispersion of particles. The velocities of fine fragments after the micro-explosive dispersion of a fuel melt droplet were established when the air temperature was varied in the range of 700–1000 °C. The gas–vapor mixture temperature in the region of the fuel gas-phase combustion was determined using the original two-color pyrometry technique.

Mapping Abandoned Cropland Changes in the Hilly and Gully Region of the Loess Plateau in China

As a form of land marginalization, abandoned cropland has an important impact on food security and the effective supply of agricultural products. With rapid urbanization across the world, large areas of cropland are abandoned in some regions, especially in mountainous and hilly areas with poor terrain. Due to the fine fragmentation and scattered distribution of abandoned cropland, and considering differences in the abandoned and fallow time of cropland, it is difficult to extract information using remote sensing technology. Therefore, this paper proposes a change in the detection method for extracting abandoned cropland information based on identifying the annual land use trajectory. Based on Landsat satellite data, annual land use was mapped from 2011 to 2020 in Gaolan County, which is located in the hilly and gully region of the Loess Plateau of China, using the random forest classification method. Subsequently, abandoned cropland information in Gaolan County was extracted, based on the land use change trajectory and analysis of the influencing factors of abandoned land. The results showed that: (1) The overall accuracy of land use interpretation in Gaolan County ranged from 86.44% to 95.45%, from 2011 to 2020, with a kappa coefficient of up to 0.93, and the classification results were ideal. (2) The recall of extracted abandoned cropland was 81%, the extraction accuracy of which was relatively high. (3) From 2013 to 2020, the cropland abandonment rate in Gaolan County ranged from 8.41% to 19.65%, with an average of 14.55%, which increased and then decreased. The abandonment rate was highest in 2015 but it then decreased year by year. The average period of abandoned cropland was 4.2 years. (4) The influence factors of the plot scale explain the difference in the spatial distribution of cultivated land abandonment. The higher the slope condition, the lower the soil nutrient content and the greater the possibility of abandonment.

Observations of Shock Propagation through Turbulent Plasma in the Solar Corona

Abstract Eruptive activity in the solar corona can often lead to the propagation of shock waves. In the radio domain the primary signature of such shocks are type II radio bursts, observed in dynamic spectra as bands of emission slowly drifting toward lower frequencies over time. These radio bursts can sometimes have an inhomogeneous and fragmented fine structure, but the cause of this fine structure is currently unclear. Here we observe a type II radio burst on 2019 March 20th using the New Extension in Nançay Upgrading LOFAR, a radio interferometer observing between 10–85 MHz. We show that the distribution of size scales of density perturbations associated with the type II fine structure follows a power law with a spectral index in the range of α = −1.7 to −2.0, which closely matches the value of −5/3 expected of fully developed turbulence. We determine this turbulence to be upstream of the shock, in background coronal plasma at a heliocentric distance of ∼2 R ⊙. The observed inertial size scales of the turbulent density inhomogeneities range from ∼62 Mm to ∼209 km. This shows that type II fine structure and fragmentation can be due to shock propagation through an inhomogeneous and turbulent coronal plasma, and we discuss the implications of this on electron acceleration in the coronal shock.

Impact of an ice particle onto a dry rigid substrate: Dynamic sintering of a residual ice cone

Ice particle impact onto a cold dry rigid substrate leads to particle deformation and breakup. If the impact velocity is high enough, the deformation is governed mainly by inertial and plastic stresses. Particle deformation may lead to the development of multiple cracks and the formation of a fragmented particle zone in the vicinity of the target surface. Moreover, a small solid residual ice cone, formed from fine particle fragments, remains attached to the substrate.In the present study the normal impact of nearly spherical ice particles, their deformation and fragmentation are observed using a high-speed video system. The size and mass of the residual ice cone are measured for impact velocities ranging from 11.2ms-1 to 73.2ms-1 and initial particle diameters ranging from 1.89mm to 4.44mm.A theoretical model for the ice particle collision and deformation is used to estimate the residual ice cone size. The model is based on a hydrodynamic approach describing particle deformation and is able to predict well the maximum radius of impression and the collision duration. The radius of the impression is used as the main length scale for an empirical model for the geometry of the residual ice cone.

Study on the relationship between fuel fragmentation during a LOCA and pellet microstructure

ABSTRACT To systematically examine the relationship between the fuel fragmentation during a loss-of-coolant accident (LOCA) and the pellet microstructure, heating tests were conducted on micro fuel samples obtained from various radial positions of high-burnup fuel. The extent of the fuel fragmentation was evaluated via fission gas release rate and post-test microscopies. The results provide direct evidence for the contribution of the high-burnup structure (HBS) on the fine fuel fragmentation during a LOCA. The paper also demonstrates that the samples with a local burnup of lower than 72 GWd/tU did not fragment severely, which is in good agreement with the previously proposed burnup threshold. Heating tests incorporating stepwise depressurization from high pressure were also conducted to examine the evolution of fission gas release throughout the depressurization. The suppressing effect of hydrostatic pressure on fuel fragmentation is further confirmed. Additionally, the paper also provides results that suggest that most of the fine fragmentation at the HBS occurs during depressurization from 20 to 2 MPa.

Segregation of dockage and foreign materials in wheat during loading into a 10-m diameter corrugated steel bin

Segregation of dockage and foreign materials (DFM) is an unavoidable phenomenon in bulk grain and causes many problems. In this study, distributions of DFM, and shrunken and broken kernels (SBK) were determined during loading of wheat in a 10-m diameter flat-bottom cylindrical bin. Wheat was loaded through a vertical funnel (spout) into the bin from five drop heights (1.6, 2.5, 3.4, 4.3 and 5.2 m). Samples were collected using a sampling tube (29 cm diameter and 50 cm deep) inserted vertically at five locations (0.00, 1.25, 2.50, 3.75 and 5.00 m of horizontal distances from the center) along three radii of the bin for each drop height. The impurities from each collected sample were divided into five categories with different sizes (other grains, other particles, SBK, fine particles, and dust and fragments) by sieving analyses. Impurities larger and smaller than wheat kernels were categorized as large and small impurities, respectively. Drop height significantly influenced the radial distribution of fine particles, dust and fragments, but not the distribution of other grains and other particles. Fine particles and dust and fragments mainly accumulated in the center, while SBK accumulated mostly near the wall of the bin. Both true density and apparent test weight (bulk density) of unclean wheat and test weight of clean wheat significantly changed along the radius of bin. Apparent test weight of unclean wheat was minimum in the center and close to the wall of bin. Drop height did not influence true density and apparent test weight of clean and unclean wheat. Thousand kernel weight, dimensions, and sphericity of wheat kernels were similar at different radial locations of bin for all drop heights. This study can be used as a reference for further studies on grain handling and associated effects on grain grading system and design of aeration, drying, and insect control. .

Controlled Fragmentation of Urinary Stones as a Method of Preventing Inflammatory Infections in the Treatment of Urolithiasis (Experience in Successful Clinical Use).

The introduction of technologically advanced methods of lithotripsy into medical practice changes the nature of postoperative complications. Among them, the main complications are inflammatory infections. This largely determines the search for new, improved methods of stone fragmentation avoiding small stone fragments and dissemination of the pelvicalyceal system of the kidney with stone-associated infection. The authors have developed a method for controlled stone fragmentation using a continuous-wave diode laser with a hot-spot effect at the optical fiber end.The aim of the study was to evaluate the efficacy of controlled urinary stone fragmentation using a continuous-wave diode laser with a highly heated distal end of the optical fiber light guide as a method of preventing inflammatory infections in clinical practice.Materials and MethodsWe analyzed 1666 case histories of urolithiasis patients who underwent percutaneous nephrolithotripsy/ nephrolithoextraction and contact ureterolithotripsy/ureteroextraction, we also performed a prospective analysis of complications based on the Clavien–Dindo classification in 90 patients who underwent fine fragmentation of stones with various lithotripters: ultrasonic, pneumatic, and holmium laser. The method of controlled stone fragmentation by a diode laser with a hot-spot effect was tested on postoperative samples of 26 renal calculi. For the first time in clinical practice, this method was tested in the bladder cavity (n=10).ResultsIn the percutaneous nephrolithotripsy group, postoperative infectious and inflammatory complications occurred in 34.1% of cases, in the percutaneous nephrolithoextraction group — in 24.6%, in the contact ureterolithotripsy group — in 7.8%, in the ureterolithoextraction group — in 2.5%. The analysis made it possible to identify factors promoting the development of infectious and inflammatory complications. For the first time in clinical practice, there were successfully performed ten operations of stone fragmentation using a continuous-wave diode laser with a hot-spot effect. Controlled coarse fragmentation of stones providing the possibility to reduce the number of infectious and inflammatory complications was performed in the bladder as a model for testing the method.ConclusionThe method of laser-induced controlled coarse fragmentation of stones with a hot-spot effect, developed and tested in clinical practice, is promising for the prevention of infectious and inflammatory complications in patients with potentially infected stones since their fine fragmentation and, consequently, spread of stone-associated toxins and microflora within the urinary system is avoided.

Energy Release and Fragmentation of Brittle Aluminum Reactive Material Cases

AbstractCylindrical reactive material cases produced by the consolidation of an aluminum powder were tested via explosive launch in a closed chamber. One configuration measured the quasistatic overpressure generated by the case and explosive, and two further tests focused on soft‐catch of fragments before and after striking the chamber walls. On a volumetric basis, the reactive material cases produced two to three times the combustion energy of an aluminum 6061 alloy case or a bare nitromethane explosive that was tested as comparisons. The metal combustion primarily occurs after case fragments impact the walls. Increasing the reactive material case thickness produces a higher pressure but lower combustion efficiency per unit mass, despite producing comparable or slightly more fine fragments on a per gram basis. Though the brittle, pressed aluminum cases have low toughness and tensile strength, recovered fragment patterns show a range of fragment sizes up to 1 mm, with approximately one‐third of the mass below 100 μm.

Impact breakage of single pharmaceutical tablets in an air gun

Milling is commonly used for controlling the size distribution of granules in the pharmaceutical dry granulation process. A thorough understanding of the breakage of single compacts is crucial in unravelling the complex interactions that exist between different pharmaceutical feed materials and the mill process conditions. However, limited studies in the literature have examined the impact breakage of single pharmaceutical compacts. In this study, pharmaceutical powders including the microcrystalline MCC 101, MCC 102 and MCC DG were compressed at different pressures and tablets with different porosities and thicknesses were produced. Impact breakage tests were conducted in an air gun and the tablet impact velocities and breakage patterns were analysed using a Phantom ultrahigh-speed camera. It was observed that the tablet breakage rate and the amount of fines reduced as the tablet porosity decreased. In addition, thin tablets with low porosity exhibited semi-brittle fracture and less intense crack propagation while thick tablets with high porosity primarily disintegrated into fine fragments. Thus, this study provides a better understanding of the breakage behaviour of different pharmaceutical materials and can potentially be used to describe the breakage modes of compacts in the ribbon milling processes.

Modeling of the Interaction between a Rock Being Processed and a Vibratory Jaw Crusher

In this article, a model of the interaction between the jaw of a vibratory jaw crusher with the rock under processing in the form of a lump material is considered. To describe the motion of the rock and its sequential fracture into finer fragments, the crushing chamber is divided into zones of equal height. In each current zone, the material to be processed breaks into smaller fractions after a definite number of loading cycles and is then moved to the next zone where it is crushed further. The material being crushed in the current zone is described by a phenomenological model that considers the viscoelastic properties and reproduces the process of the sequential fracture of the material under processing upon multiple compressions. Differential equations of the jaw movements have been derived that consider the layer-by-layer interaction with the rock under processing. The amplitudes of the vibrations of the jaw with time and the distribution of the forces over the length of the jaw have been analyzed.

Effect of Kota stone slurry on strength properties of cement mortar mixes

Rajasthan, state of India is known for its rich availability of minerals and stones like quartz, feldspar, gypsum, marble, sandstone, Kota stone etc. Mining of these materials required lots of energy in terms of their processing and disposing of waste. Fine fragment generated during polishing of stones is a serious issue for human health as well as environment. Present study was focused on mortar mixes (1:5) containing Kota stone slurry as substitution of cement from 0% to 20% with steps of 2.5% for cement. Total nine mortar mixes were studied on the basis of water absorption, density, compressive, flexural, tensile and adhesive strength. Results of the study reveal that the kota stone slurry has possibility to use as part of cement up to 10% replacement.

Generation of particles and fragments by quasicontinuous wave fiber laser irradiation of stainless steel, alumina, and concrete materials

An experimental characterization is presented on fine particles, droplets, and fragments produced at the interaction region between a 2.7 kW quasicontinuous wave (repetitive pulsed operation with a 10 ms pulse duration) fiber laser and stainless steel, alumina, and heavy concrete samples. In the samples, the recoil pressure induced by vaporization pushes particles and fragments into the ambient atmosphere. In order to preserve a safe working environment, in particular for nuclear decommissioning, special care should be taken to confine and retrieve such particles during laser processing. In the experiments, particle production from the vapor and the molten phase layer in the targeted material was observed with a high-speed camera, with fine particles collected and analyzed using an electron microscope. The observed results were qualitatively interpreted with the help of a simplified one-dimensional hydrodynamic code coupled with a stress computation code. Characterization and classification of the results are expected to provide a useful database that will contribute to the decommissioning of nuclear facilities and other industrial applications.

Decrypting silicic magma/plug fragmentation at Azufral crater lake, Northern Andes: insights from fine to extremely fine ash morpho-chemistry

Azufral (SW Colombia) is a dangerous silicic volcano hosting a crater lake, which serves as an excellent example of an incipient plug disruption through phreatomagmatism. We studied the youngest succession of dilute pyroclastic density currents (PDCs) onlapping the north-eastern crater rim. Scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy was used to carry out an automated single-particle analysis of fine to extremely fine ash. We were able to obtain fast and accurate chemical analysis and imaging of 15,098 particles within the 250–63-μm and the 63–32-μm size ranges. The 2D form and roughness parameters were determined for 4895 juvenile glassy particles and validated by 3D micro-X ray computer tomography. There are two end members of high (group 1) and low (group 2) roughness juvenile glassy particles. Group 1 comprises high-roughness glass particles with solidity values as low as 0.34 in 2D and 0.33 in 3D, and convexity values as low as 0.33 in 2D and 0.26 in 3D. Group 2 comprises low-roughness glass particles with 2D solidity values > 0.79 and 3D solidity values typically > 0.58. In this group, 2D convexity values are > 0.68 and 3D convexity values are > 0.71. Both end members are mostly discriminated by the 2D Concavity Index (0.14 to 0.77 in group 1 vs. 0.05–0.35 in group 2). The remaining group 3 comprises particles of intermediate roughness values. In this study, we show how an incipient plug developed over a short repose time might be subjected to only a few cycles of vesicle nucleation, collapse and densification, retaining the characteristics of juvenile glass. Each glassy juvenile ash type, defined by a particular morphology, roughness and microtexture can be linked to a density “stratified” conduit model. In Azufral, the capping and conduit lining dense regions and the permeable zones of the incipient plug likely cracked. The newly formed cracks could allow hydraulic forcing caused by external water and induce phreatomagmatic interaction. This interaction favoured the fine fragmentation of the plug while enhancing ongoing magmatic processes. Finally, the variations of bulk componentry provided clues on dilute pyroclastic density current transport and physical fractionation processes by secondary fragmentation, elutriation and interaction with the crater rim.

Isotopic Composition of Noble Gases, Nitrogen, and Carbon in the Ozerki New L Chondrite

The isotopic composition of noble gases, nitrogen, and carbon in two samples of the Ozerki L chondrite, which differ in the degree of impact metamorphism, analyzed by the methods of stepwise oxidation and crushing, is reported. The data obtained indicate that the meteorite contains gases trapped on the asteroid during the impact events. The isotopic composition of trapped argon, studied by the stepwise crushing method, is dominated by radiogenic 40Ar (the average 40Ar/36Ar values are 846 in the chondrite material and 1908 in the melt with fine chondrite fragments). Most of the trapped 36Ar is located in positions inaccessible for crushing. The isotopic composition of Ne is a mixture of the solar-wind neon, cosmogenic, and most likely planetary (Q) components. The elemental composition of the trapped noble gases is formed by mixing of the solar, planetary (Q), and cosmogenic components in different proportions. Diffusion processes caused by impact events most likely influenced the elemental abundance of noble gases, primarily helium. Almost all carbon and nitrogen are chemically bound in the rock. In general, their isotopic composition corresponds to that of ordinary chondrites; however, an atypically light carbon isotopic composition with a bulk value δ13C = –47.6 ± 4.8 (‰) was detected in a sample of the chondrite material. The nitrogen released during crushing is isotopically lighter than that released during oxidation. This may indicate that in the course of impact processes, solar nitrogen is more easily mobilized and redistributed into voids than organic nitrogen enriched in the heavy isotope.

Characterization of high-temperature nuclear fuel-coolant interactions through X-ray visualization and image processing

High-resolution X-ray imaging was employed at the JAEA MELT facility to visualize a kilogram-scale interaction between a jet of high temperature molten stainless steel and sodium, mimicking a sodium-cooled fast-neutron reactor in the aftermath of a core-disruptive accident. A novel software, SPECTRA, has been developed for the quantitative characterization of jet quenching and fragmentation. Tracking and 3D reconstruction of the melt phase traversing the imaging window enabled the detection of 72% of the debris mass recovered post-experiment. The rebounding of melt fragments confirmed a solid outer crust at the melt-coolant interface, while a thermal fragmentation event induced rapid vapor expansion. Jet fragmentation is best explained by the vaporization of coolant entrained within the melt jet generating an internal over-pressure sufficient for fragmentation of the crust. Thermal fragmentation produced missiles with velocities exceeding that of the jet, and a bimodal debris size distribution of coarse jet shells and finer fragments.

Interpretation of breakage characteristics of particle beds from confined compression tests

This paper presents an investigation into the size reduction characteristics of particle beds under confined compression. The test data were chosen from a series of specifically designed compression tests and factors including particle materials, feed size and gradations were considered. Through extensions of previous appearance functions mostly applied in single particle breakage tests, we established descriptive functions for fragmentation degree indices using input energy and particle size, and developed relationships between characteristic indices to predict size reduction. Based on the established correlations, some discussions on fine products distribution and the applicability of self-similarity are also presented. Our test results, particularly the distribution of fine fragments, demonstrate the suitability of self-similarity in the product size distributions after sufficient compression and breakage. The present study is deemed as a supplement to the existing approaches for describing the size reduction response.

The ballistic impact performance of nanocrystalline zirconia-toughened alumina (nZTA) and alumina ceramics

The ballistic impact performance of nanocrystalline zirconia-toughened alumina (nZTA) ceramics, comprising 15 wt% nano-yttria-stabilised zirconia in a sub-micron alumina matrix, have been studied through depth of penetration tests and compared to the results for monolithic alumina. The penetration resistance of each material was evaluated by fitting the penetration depth results against the thickness of the ceramic targets. These results show that, despite micro-Raman analysis of the nZTA confirming the occurrence of the classic tetragonal-to-monoclinic zirconia phase transformation, nZTA ceramics provide no benefit with respects to penetration resistance compared to monolithic alumina. Analysis of the fragments generated using Cr3+/Al2O3 fluorescence spectroscopy shows that both the nZTA and alumina experience similar amounts of plastic deformation as a function of fragment size, with finer fragments (<150 μm) exhibiting more plastic deformation than coarser fragments (>150 μm). These results are validated through fracture surface observations and subsurface dislocation analysis using SEM and TEM respectively.

Ductile damage and fragmentation of highly porous γ-alumina under multi-point crushing test

Mechanical behavior of highly porous alumina catalytic supports is investigated through a non-conventional approach consisting in a multi-point crushing of individual cylindrical extrudates. A ductile behavior characterized by irreversible deformation and fragmentation phenomena is observed and pointed out by experimental load-displacement curves. SEM fractographies of the fragments collected after the tests confirm the presence of dense micro-cracking and of local deformations under contact zones. A Finite Element analysis of the test shows that a Drucker-Prager strength criterion associated with a perfectly plastic flow rule mimics the global damageable behavior of the specimen under the multi-point crushing test. A correlation is proposed between the evolution of the mass of fine fragments and the plastic energy dissipation.