Fragment Size Research Articles

Pathomorphological changes in laboratory animals exposed to lethal doses of disinfec-tants

The use of disinfectants is a crucial aspect of preventive and health improvement measures for infectious diseases in farm and domestic animals. Regulatory documents require the determination of toxicity to macroorganisms, including the establishment of lethal doses and toxicity groups, during the development and registration of antimicrobial agents. This study aimed to investigate the histological changes in the internal organs of laboratory animals when determining lethal doses of innovative disinfectants. The experiments used domestic disinfectants containing glutaraldehyde as the active ingredient. Histological studies were conducted on the internal organs (kidney, liver, stomach, intestines, and spleen) of 75 laboratory animals using an Axioskop 40/40FL microscope (Carl Zeiss, Germany) with video microscopic photography. The methods used were under current standards. Hemodynamic disorders were observed in the renal tissue under the influence of lethal doses of aldehyde disinfectants. These disorders were characterized by capillary dilation and blood filling. Glomerular capillary dilation and overflow with blood cells were also detected. Additionally, stasis was observed in the lumen of the microcirculatory vessels throughout the entire length. The examination of histological sections from animal liver samples revealed a significant expansion of Dissé spaces, variations in the size of hepatocyte nuclei, beam decomposition and fragmentation, small acute perivascular hemorrhages, leukostasis in sinusoids, and hemodynamic disorders. The structure of the organ's beams was also disturbed, and a significant number of venous vessels were dilated and excessively filled with blood cells. Minor changes were detected in the stomach, including desquamation of the epithelial cells of the glands and their exfoliation into the gastric lumen, as well as circulatory disorders. Epithelial desquamation, blood vessel dilation, and signs of connective tissue edema were observed in the intestine. The kidneys exhibited signs of acute venous hemorrhage and stasis in vessels of various calibers, with the development of small acute parenchymal hemorrhages and localized lymphoid cell death in the white pulp. The prospect of further research is to investigate the histomorphological changes in the internal organs of laboratory animals when exposed to modern complex disinfectants with different active ingredients.

Evaluation of Mixing Effects and Particle Breakage on a Cross Flow Turbine with DEM

AbstractVarious effects during conveying and storage processes lead to size segregation of bulk material, but many applications require a mostly constant particle size distribution. Especially during bunker filling, segregation effects are noticed, which are further intensified by possible core flow effects. In order to reduce segregation effects during bunker filling, a cross flow turbine is installed at a bunker used for storage of blast furnace sinter. In this contribution, discrete element simulations were performed to analyze mixing effects and possible particle breakage due to the cross flow turbine. Significant mixing effects during bunker filling are noticed due to the cross flow turbine. The results show a more evenly distributed bunker outflow in terms of particle size.Particle breakage is analyzed by means of a newly developed breakage model for the Discrete Element Method (DEM). The model is based on a probabilistic particle replacement with voronoi-tessellated fragments. The validated breakage model allows high accuracy in prediction of fragment size distribution. Fragments are further breakable, which allows simulation of processes with several damaging effects. The breakage model was calibrated with a specially developed automated single particle impact tester for rapid analysis of breakage characteristics of bulk materials.

Automatic detection and characterization of discontinuity traces and rock fragment size distribution using a digital image processing method

Rock materials naturally contain cracks and fractures, which may produce rock fragments or grains under geological and engineering conditions. Identification and characterization of the spatial extent of discontinuity traces and size distribution of fragments/grains are prerequisites for accurate geomechanical assessments of the stability of rocks containing natural or artificial discontinuities. This study introduces an advanced image processing methodology that leverages color gradient analysis and multi-threshold criteria to effectively detect and delineate fracture traces or boundary outlines. Furthermore, this approach facilitates the acquisition of precise fragment or grain size distribution statistics. To comprehensively characterize these discontinuity traces, the methodology employs the calculation of fractal dimensions alongside the use of an equivalent diameter conversion technique. These tools enable the quantification of the complexity and size distribution of the fragments or grains. The efficacy of this approach has been demonstrated through a series of case studies, encompassing a wide range of applications including digital images from numerical simulations, experimental tests, field observations, and micrographic analyses of rock structures. In these studies, the method proved capable of satisfactorily calculating the fractal dimensions of fractures, cracks, and contacts. Simultaneously, it accurately and efficiently determined the size distribution, as evidenced by frequency histograms and cumulative distribution curves obtained from the images. In essence, the proposed approach provides an automatic quantitative methodology to identify and characterize macroscopic and microscopic rock structures containing discontinuity traces or comprised of fragments/grains. This advancement holds significant potential for enhancing the precision and efficiency of geological and geomechanical assessments.

Characterization of microplastics in outdoor and indoor air in Ranchi, Jharkhand, India: First insights from the region

The study focused on detecting and characterizing microplastics in outdoor and indoor air in Ranchi, Jharkhand, India during post-monsoon (2022) and winter (2023). Stereo microscopic analysis showed that plastic fibres had a dominant presence, fragments were less abundant, whereas fewer films could be detected in indoor and outdoor air. The atmospheric deposition of microplastics outdoors observed 465 ± 27 particles/m2/day in PM10 and 12104 ± 665 and 13833 ± 1152 particles/m2/day in PM2.5 in quartz and PTFE, respectively during the post-monsoon months. During winter, microplastic deposition rates in PM10 samples were found to be 689 ± 52 particles/m2/day and 19789 ± 2957 and 30087 ± 13402 in quartz and PTFE particles/m2/day respectively in PM2.5. The mean deposition rate in indoor environment during post-monsoon was 8.3 × 104 and 1.03 × 105 particles/m2/day in winter. During the post-monsoon period in PM10, there were fibres from 7.7 to 40 μm and fragments from 2.3 μm to 8.6 μm. Indoor atmospheric microplastics, fibres ranged from 1.2 to 47 μm and fragments from 0.9 to 16 μm present respectively during the post-monsoon season. Fibres and fragment sizes witnessed during winter were 3.6–6.9 μm and 2.3–34 μm, respectively. Indoor air films measured in the range of 4.1–9.6 μm. Fourier transform infrared analysis showed that outdoor air contained polyethylene, polypropylene, Polystyrene, whereas indoor air had polyvinyl chloride. Polyethylene mainly was present in outdoor air, with lesser polypropylene and polystyrene than indoors, where polyvinyl chloride and polyethylene were in dominant proportions. Elemental mapping of outdoor and indoor air samples showed the presence of elements on the microplastics. The HYSPLIT models suggest that the particles predominantly were coming from North-West during the post-monsoon season. Principal component analysis indicated wind speed and direction influencing the abundance of microplastics. Microplastics concentration showed strong seasonal influence and potential to act as reservoir of contaminants.

Lost needle in the oral cavity: can the nightmare be just a bad dream?

The loss of a scalpel or a needle during surgery can threaten the health of the patient and lead to additional costs, and radiographical assistance during surgery has been the only recovery method. This study evaluates the efficacy of a metal detector compared with conventional radiology for recovering a needle lost in the oropharynx during surgery. Different fragment sizes of needles normally used in pharyngoplasty were embedded at different locations and depths in a lamb's head. Three experienced and three junior otolaryngologists searched for the needle fragments using a metal detector and conventional radiology. All fragments were found with each method, but the mean searching time was 90 per cent shorter with the metal detector. A metal detector can be a useful tool for locating needles that break during ENT surgery, as it requires less time than conventional radiology and avoids exposing patients to radiation.

Multidimensional Spatial Vitality Automated Monitoring Method for Public Open Spaces Based on Computer Vision Technology: Case Study of Nanjing’s Daxing Palace Square

Assessing the vitality of public open spaces is critical in urban planning and provides insights for optimizing residents’ lives. However, prior research has fragmented study scopes and lacks fine-grained behavioral data segmentation capabilities and diverse vitality dimension assessments. We utilized computer vision technology to collect fine-grained behavioral data and proposed an automated spatial vitality monitoring framework based on discrete trajectory feature points. The framework supported the transformation of trajectory data into four multidimensional vitality indicators: crowd heat, resident behavior ratio, movement speed, and spatial participation. Subsequently, we designed manual validation mechanisms to demonstrate the monitoring framework’s efficacy and utilized the results to explore the changes in vitality, and the influencing factors, in a small public space. Discrete trajectory feature points effectively addressed the literature’s fragmented study scope and limited sample size issues. Spatial boundaries had a significantly positive impact on spatial vitality, confirming the “boundary effect” theory. The peak spatial vitality periods were from 08:30 to 09:30 and from 17:30 to 18:30. A higher enclosure degree and better rest facilities positively impacted spatial vitality, while a lower enclosure degree did not consistently suppress spatial vitality in all situations. Overall, spatial features and spatial vitality have a complex nonlinear relationship.

A global meta-analysis of the impacts of forest fragmentation on biotic mutualisms and antagonisms.

Forest fragmentation is a grave threat to biodiversity. Forests are becoming increasingly fragmented with more than 70% now < 1km from forest edge. Although much is known about the effects of forest fragmentation on individual species, much less is understood about its effects on species interactions (i.e., mutualisms, antagonisms, etc.). In 2014, a previous meta-analysis assessed the impacts of forest fragmentation on different species interactions, across 82 studies. We pooled the previous data with data published in the last 10 years (combined total 104 studies and 168 effect sizes). We compared the new set of publications (22 studies and 32 effect sizes) with the old set to evaluate potential changes in species interactions over time given the global increase in fragmentation rates. Mutualisms were more negatively affected by forest fragmentation than antagonisms (p < 0.0001). Edge effects, fragment size, and degradation negatively affected mutualisms, but not antagonisms, a different finding from the original meta-analysis. Parasitic interactions increased as fragment size decreased (p < 0.0001)-an intriguing result at variance with earlier studies. New publications showed a more negative mean effect size of forest fragmentation on mutualisms than old publications. Although research is still limited for some interactions, we identified an important scientific trend: current research tends to focus on antagonisms. We concluded that forest fragmentation disrupts important species interactions and that this disruption has increased over time.

Heterozygosity is low where rare color variants in wild carnivores prevail.

Coat color and pattern are a distinguished feature in mammalian carnivores, shaped by climatic cycles and habitat type. It can be expressed in various ways, such as gradients, polymorphisms, and rare color variants. Although natural selection explains much of the phenotypic variation found in the wild, genetic drift and heterozygote deficiency, as prominent in small and fragmented populations, may also affect phenotypic variability through the fixation of recessive alleles. The aim of this study was to test whether rare color variants in the wild could relate to a deficiency of heterozygotes, resulting from habitat fragmentation and small population size. We present an overview of all rare color variants in the order Carnivora, and compiled demographic and genetic data of the populations where they did and did not occur, to test for significant correlations. We also tested how phylogeny and body weight influenced the presence of color variants with phylogenetic generalized linear mixed models (PGLMMs). We found 40 color-variable species and 59 rare color variants. In 17 variable phenotypic populations for which genetic diversity was available, the average A R was 4.18, H O = 0.59, and H E = 0.66, and F IS = 0.086. We found that variable populations displayed a significant reduction in heterozygosity and allelic richness compared to non-variable populations across species. We also found a significant negative correlation between population size and inbreeding coefficients. Therefore, it is possible that small effective size had phenotypic consequences on the extant populations. The high frequency of the rare color variants (averaging 20%) also implies that genetic drift is locally overruling natural selection in small effective populations. As such, rare color variants could be added to the list of phenotypic consequences of inbreeding in the wild.

Restoration and Transformation: The Response of Shocked and Oxidized Magnetite to Temperature

AbstractLarge impact craters on Earth are associated with prominent magnetic anomalies, residing in magnetite of the shocked target rocks and impactites. Shock experiments on magnetite suggest that up to 90% of magnetic susceptibility is lost at pressures &gt;5 GPa, but can be partially restored by post‐shock thermal annealing. The magnetic property changes are caused by shock induced grain size reduction and fragmentation, as well as domain wall‐pinning at crystal lattice defects. A recent study of granitoids from the peak‐ring of the Chicxulub crater found that annealing may occur naturally, but can also be overprinted by high‐temperature hematite‐to‐magnetite transformation in non‐oxidizing environments. In this study, we isolate the effect of defect annealing and hematite‐to‐magnetite transformation using the evolution of hysteresis, isothermal remanent magnetization components and first order reversal curve (FORC) diagrams at different high‐temperature steps. We used a laboratory‐shocked magnetite‐quartz ore, a non‐shocked naturally oxidized granite, and a naturally shocked and oxidized granite. Our findings suggest that annealing of shock‐induced lattice defects partially restores some pre‐shock magnetic behavior and causes an apparent average bulk‐sample domain state increase. Hematite‐to‐magnetite transformation creates new fine‐grained magnetite that strongly overprints the original signal, and decreases the average bulk‐sample domain state. Where annealing and hematite‐to‐magnetite transformation both occur, the new magnetite masks the annealing‐induced property restoration and apparent domain state modification in the shocked magnetite. As magnetite oxidation is a ubiquitous process in surface rocks, these findings are fundamental to understand hematite‐to‐magnetite transformation as a potential overprint mechanism, and could have broad implications for paleomagnetic interpretations.

Robustness of steady state and stochastic cyclicity in generalized coalescence-fragmentation models

Processes of coalescence and fragmentation are used to understand the time-evolution of the mass distribution of various systems and may result in a steady state or in stable deterministic or stochastic cycles. Motivated by applications in insurgency warfare we investigate coalescence-fragmentation systems. We begin with a simple model of size-biased coalescence accompanied by shattering into monomers. Depending on the parameters this model has an approximately power-law-distributed steady state or stochastic cycles of alternating gelation and shattering. We conduct stochastic simulations of this model and its generalizations to include different kernel types, accretion and erosion, and various distributions of non-shattering fragmentation. Our central aim is to explore the robustness of the steady state and gel-shatter stochastic cycles to these variations. We show that an approximate power-law steady state persists with the addition of accretion and erosion, and with partial rather than total shattering. However, broader distributions of fragment sizes typically vitiate both the power law steady state and gel-shatter cyclicity. This work clarifies features shown in coalescence/fragmentation model simulations and elucidates the relationship between the microscopic dynamics and observed phenomena in this widely applicable interdisciplinary model type.Graphical abstract

Structure and composition of avifauna in two forest areas in Western Amazonia

The Amazon region boasts one of the world's greatest diversities of bird species and the highest in Brazil. However, overexploitation and habitat destruction have affected all animal species, particularly birds. Forest fragmentation leads to habitat reduction, species impoverishment, and alters the composition of the avifauna community. Therefore, it is crucial to understand the arrangement of bird communities in these areas to guide conservation efforts. This study aimed to describe and compare the structure of bird communities in two forest fragments of different sizes and proximity to urban areas in the municipality of Cruzeiro do Sul, Acre. Using MacKinnon's list methodology, bird communities were sampled in two areas, recording a total of 189 species. The larger rural area, with lower anthropogenic influence, exhibited higher species richness (n=148), with groups more specialized in terms of habitat and diet and sensitive to environmental changes, indicating greater species diversity. In contrast, the smaller urban area had fewer species (n=77), mostly belonging to generalist groups. The data revealed differences in bird communities between the locations, with the larger fragment less affected by human presence showing greater species diversity and hosting more species sensitive to environmental changes and dietary specialists.

Impact of forest fragmentation and associated edge effects on the population density of four nocturnal lemur species in North West Madagascar

AbstractThe clearing and fragmentation of tropical forests is the single biggest threat to primate populations who depend on this habitat for survival. In contrast to primates that live in continuous, undisturbed forests, primate communities of fragmented forests need to adapt to decreased food availability and increased inter‐ and intraspecific competition typical of these degraded and anthropogenically disturbed habitats. Some primate species are highly sensitive to habitat fragmentation, whilst other species can adapt and even thrive in fragmented and degraded forests. Here, we assessed how forest fragmentation and associated edge effects impact the population density of four species of nocturnal lemur in the Sahamalaza‐Iles Radama National Park, North West Madagascar. We conducted 118 transect walks over a 3‐year period covering a total distance of 107 km to collect encounter rate (N/km) and population density (N/Ha) data for each species, which we then compared between the edge and core areas of a continuous forest and a fragmented forest. Our results were highly species‐specific, with the population densities of two species (Lepilemur sahamalaza and Microcebus sambiranensis) increasing in edge and fragmented habitat, whilst we observed the opposite for Cheirogaleus medius. Mirza zaza density appeared consistent between the continuous and fragmented forest and in both edge and core areas. We also found evidence of species‐specific population density relationships with fragment size, core area and fragment shape; however, further work is needed to support these findings. This study demonstrates that some nocturnal lemurs can adapt to degraded habitats and thrive within fragmented forests, whilst other species are less capable of doing so.

Numerical study on perforation damage and fragmentation of reinforced concrete slab under close-in explosion

Reinforced concrete (RC) structure is prone to suffer localized damage when exposed to close-in explosions. Spalling damage might occur due to the reflected tensile stress wave exceeding the concrete dynamic tensile strength. When the blast wave is intensive enough, it can also cause significant crushing damage on the contact surface, potentially leading to perforation when the crushing depth aligns with the spalling depth. This perforation/spalling damage can generate a large number of secondary fragments with high ejecting velocities. Additionally, the blast wave might pass through the perforation hole and cause further acceleration of the secondary fragments. In the author’s previous study, an ALE-FEM-SPH numerical model was established and validated with the existing testing data for the prediction of spalling damage as well as fragment sizes and velocities. As a continuous work, this study conducts numerical simulations to predict the perforation damage and fragmentation under higher-intensity blast loading. The results including centre perforation hole, spalling area on back surface, fragment ejecting velocities, fragment landing distance and fragment characteristics distributions are reported and studied. The acceleration effect on the secondary fragments by the traversed blast wave that further carries the fragments flying is also investigated. The numerical results show that using the scaled distance Z might not reliably quantify the perforation/spalling damage under close-in cylindrical TNT explosion. Given the identical scaled distance, the scenarios with different combinations of charge weight and standoff distance can result in large variations up to 300% in the predictions of damaged area and 50% for the maximum fragment ejecting velocities, respectively. A scaled blast parameter Z* is suggested and the empirical formulae are proposed for better quantification of the damaged area of RC slab as well as the fragment velocity and kinetic energy under close-in cylindrical TNT explosions.

Non-invasive detection of lymphoma with circulating tumor DNA features and protein tumor markers.

According to GLOBOCAN 2020, lymphoma ranked as the 9th most common cancer and the 12th leading cause of cancer-related deaths worldwide. Traditional diagnostic methods rely on the invasive excisional lymph node biopsy, which is an invasive approach with some limitations. Most lymphoma patients are diagnosed at an advanced stage since they are asymptomatic at the beginning, which has significantly impacted treatment efficacy and prognosis of the disease. This study assessed the performance and utility of a newly developed blood-based assay (SeekInCare) for lymphoma early detection. SeekInCare utilized protein tumor markers and a comprehensive set of cancer-associated genomic features, including copy number aberration (CNA), fragment size (FS), end motif, and lymphoma-related virus, which were profiled by shallow WGS of cfDNA. Protein marker CA125 could be used for lymphoma detection independent of gender, and the sensitivity was 27.8% at specificity of 98.0%. After integrating these multi-dimensional features, 77.8% sensitivity was achieved at specificity of 98.0%, while its NPV and PPV were both more than 92% for lymphoma detection. The sensitivity of early-stage (I-II) lymphoma was up to 51.3% (47.4% and 55.0% for stage I and II respectively). After 2 cycles of treatment, the molecular response of SeekInCare was correlated with the clinical outcome. In summary, a blood-based assay can be an alternative to detect lymphoma with adequate performance. This approach becomes particularly valuable in cases where obtaining tissue biopsy is difficult to obtain or inconclusive.

Vision-based size distribution analysis of rock fragments using multi-modal deep learning and interactive annotation

Real-time size distribution analysis is of great significance to rock fragments in practical engineering. Traditional methods have struggled to strike a balance between analysis speed and precision, prompting the recent adoption of deep learning. However, prevalent approaches for estimating rock fragment sizes from RGB images (single-modality) suffer from two defects: (a)time-consuming and labour-intensive dataset annotation, (b) poor transferability between cases. To solve the above problems, a comprehensive multi-modal framework for size distribution prediction of rock fragments (SDPRF) is proposed in this paper. This framework comprises three essential components: a multi-modal image dataset generation method, a multi-modal rock surface net (Mrsnet) for fragment edge detection and a 2-step breakpoints connection algorithm. The test results indicate:(1) The generation method of SDPRF dataset greatly reduces the time required for dataset annotation, (2) Mrsnet shows better generalization ability for other cases outside the training set than traditional single-modal learning.

Evaluation of Rock and Explosive Properties for Fragmentation Characterization: An Application of WipFrag

This study investigates the rock explosive properties in selected Lokoja quarries, Nigeria, with the goal of characterizing fragmentation for optimized downstream operations. The analysis includes porosity, UCS values, and permeability assessment in Gitto quarry, highlighting advantages in material application. Comparisons between rock formations (Q1 and Q2) reveal varying compressive strengths, crucial for determining appropriate explosive energy for efficient fragmentation. Blast design parameters from Q1 and Q2 indicate consistent values, aiding in operational planning. Fragmentation analysis, conducted using WipFrag software, delineates size ranges and classifies the blast as having a moderate distribution. Correlations between blast fragmentation size and powder factor underscore the impact on efficiency. A classification chart and table are presented for convenient interpretation of results, providing valuable insights for enhancing blasting practices in Lokoja quarries and ultimately improving productivity. The fragmentation analysis result carried out in this study using WipFrag software shows that the 50%, 80% and Maximum block size passing size ranges from 539.94 – 1349.53 mm, 690.07 – 1907.81 mm, 808-2280 mm respectively. The blast fragmentation sizes are classified as moderate distribution blast based on the uniformity index value ranging from 1.95 to 2.4. The relationship between blast fragmentation size and powder factor was evaluated using linear correlation coefficient. It was noted that, X20, X50, X80 has high R2 values greater than 60% respectively

Defects in &lt;i&gt;h&lt;/i&gt;-BN: computer simulation of size effects

The influence of size effects on the properties of a hexagonal boron nitride (h-BN) monolayer containing CBVN, NBVN, and OBOBVN defects has been studied by first principles methods. These defects are potentially capable of generating single photons in quantum optics and quantum information devices. Size effects here mean the dependence of the studied model properties on the simulated fragment size of the 2D structure under periodic boundary conditions. Physically, this means that the properties of a monolayer depend on the distance between defects. This dependence allows us to judge how strongly the defects interact with each other and whether they interact at all. For technical applications, the characteristics of the band structure (band gap, spectrum and density of electron states induced by the defect in the band gap) and the atomic structure of the defect (defect formation energy, geometry in the equilibrium configuration), which form this band pattern, are important. In this work, these properties are studied by using the density functional theory with the basis of atom-like functions (SIESTA package) and plane waves (VASP package). The results obtained using both packages are consistent with each other. It has been established that the defects can be considered non-interacting, when the distance between them is ten unit cell parameters.

Assessing RNA integrity by digital RT-PCR: Influence of extraction, storage, and matrices

Abstract The development of high-throughput sequencing has greatly improved our knowledge of microbial diversity in aquatic environments and its evolution in highly diverse ecosystems. Relevant microbial diversity description based on high-throughput sequencing relies on the good quality of the nucleic acid recovered. Indeed, long genetic fragments are more informative for identifying mutation combinations that characterize variants or species in complex samples. This study describes a new analytical method based on digital Polymerase Chain Reaction (PCR) partitioning technology for assessing the fragmentation of nucleic acid and more specifically viral RNA. This method allows us to overcome limits associated with hydrolysis probe-based assay by focusing on the distance between different amplicons, and not, as usual, on the size of amplicons. RNA integrity can thus be determined as a new fragmentation index, the so-called Fragment size 50. The application of this method has provided information on issues that are inherent in environmental analyses, such as the storage impact of raw samples or extracted RNA, extraction methods, and the nature of the sample on the integrity of viral RNA. Finally, the estimation of fragment size by digital PCR (dPCR) showed a very strong similarity with the fragment size sequenced using Oxford Nanopore Technology. In addition to enabling objective improvements in analytical methods, this approach could become a systematic quality control prior to any long-read sequencing, avoiding insufficiently productive sequencing runs or biases in the representativeness of sequenced fragments.

A numerical investigation of thermal stress induced cracking pattern in the solidifying nuclear fuel droplet during MFCI

During Molten Fuel Coolant Interaction (MFCI) occurring in a Sodium-cooled Fast Reactor (SFR) following a severe accident, the corium jet breaks up into coarse droplets due to hydrodynamic instabilities and fine flaked debris are generated due to the thermal stress cracking occurring on the solidifying droplet. In particular mixed oxide core debris quenched by liquid sodium are more prone to thermal stress cracking because of the excellent heat transport properties of liquid sodium, which leads to a large temperature gradient across the crust of the ceramic fuel. In this paper, thermal stress initiated cracking of solid crust of the nuclear fuel droplet is studied using Fracture Bifurcation Theory (FBT) and Minimum Potential Energy Principle (MPEP). FBT is able to predict the minimum crack length needed for crack propagation or catastrophic failure depending on the computed KI values. On the other hand, MPEP can predict the periodic and hierarchical cracking pattern that can develop on the core debris. This helps in the prediction of number of cracks and the crack length that can develop on the solid crust. Parametric studies have been carried out by varying MOX droplet sizes, crust thickness and cooling conditions and calculating KI by semi-analytical means and comparing it with KIC. The analysis revealed that solidifying droplets with radius equal to or more than 2 mm are susceptible to thermal stress initiated crack growth and catastrophic breakage even if a few tens of micron size initial crack develops on its surface. Then a particular case of 2 mm radius core debris is considered and its cracking pattern is studied by applying MPEP. This optimal crack configuration is obtained by minimizing potential energy for a given range of crack length and spacing. The analysis has been carried out with ANSYS APDL code which calculates the strain energy for a given initial crack length and spacing. The 2D computational model is validated with a similar study carried out for Alumina disc quenched in water and the results are in good agreement. The minimum fine fragment size predicted by the analysis for mixed oxide debris is a flake like debris with equivalent radius of 41 µm when approximated to be a sphere. The particle size correlates well with the fine debris sizes reported in literature of MFCI experiments.

Hetero‐blast from a structural reactive material cylinder under explosive loading

AbstractA structural reactive material (SRM) cylinder is considered here as a limiting case of a dense metallic energetic system in which a mixture of metal particles is consolidated to the theoretical maximum density excluding porosity, to possess both high energy density and mechanical strength. Dynamic fragmentation and free‐field explosion of a 103 mm inner diameter SRM cylinder charge is experimentally studied, with a wall thickness varying in a range of metal‐to‐explosive mass ratio M/C=1.3 to 4.0. Under explosive loading, the SRM cylinder produces a designated fragment size distribution divided into two groups: fine fragments with sizes on the order of 102 μm and below, and coarse fragments with sizes on the order ranging between 100‐101 mm. Prompt detonation shock‐induced reaction (DSIR) of the expanding cloud of high‐concentration fine fragments supplements the energy to enhance the primary blast as it propagates, while the coarse fragments form a high‐speed, high‐concentration metal momentum flux crossing the fireball and blast front to contribute to the total impulse loading to a nearby structure. Rapid impact‐induced reaction (IIR) of the secondary fragments from high‐speed coarse SRM fragments further enhances the reflected blast loading or generates a high interior explosion pressure as fragments perforate into the structure. The above distinctive characteristics of a unique hetero‐blast are coupled effectively in the near‐field range.