Fragmentation Model Research Articles

Ab initio study of nuclear clustering in hot dilute nuclear matter

We present a systematic ab initio study of clustering in hot dilute nuclear matter using nuclear lattice effective field theory with an SU(4)-symmetric interaction. We introduce a method called light-cluster distillation to determine the abundances of dimers, trimers, and alpha clusters as a function of density and temperature. Our lattice results are compared with an ideal gas model composed of free nucleons and clusters. Excellent agreement is found at very low density, while deviations from ideal gas abundances appear at increasing density due to cluster-nucleon and cluster-cluster interactions. In addition to determining the composition of hot dilute nuclear matter as a function of density and temperature, the lattice calculations also serve as benchmarks for virial expansion calculations, statistical models, and transport models of fragmentation and clustering in nucleus-nucleus collisions.

A threshold model of plastic waste fragmentation: New insights into the distribution of microplastics in the ocean and its evolution over time

Plastic pollution in the aquatic environment has been assessed for many years by ocean waste collection expeditions around the globe or by river sampling. While the total amount of plastic produced worldwide is well documented, the amount of plastic found in the ocean, the distribution of particles on its surface and its evolution over time are still the subject of much debate. In this article, we propose a general fragmentation model, postulating the existence of a critical size below which particle fragmentation becomes extremely unlikely. In the frame of this model, an abundance peak appears for sizes around 1 mm, in agreement with real environmental data. Using, in addition, a realistic exponential waste feed to the ocean, we discuss the relative impact of fragmentation and feed rates, and the temporal evolution of microplastics (MP) distribution. New conclusions on the temporal trend of MP pollution are drawn.

Fuel fragmentation and relocation (FFR) model in SPACE code PART 1: Development and verification

Ballooning of cladding, which can happen during a loss of coolant accident (LOCA), causes relocation of fragmented fuel. Recently, consideration of fuel fragmentation, relocation, and dispersal (FFRD) phenomena for safety analyses has been requested by a regulatory body. Therefore, new models related to the fuel fragmentation, relocation, and dispersal (FFRD) in SPACE code have been developed. In this study, the FFR model, excluding dispersal, will be discussed. The fuel fragmentation and relocation models, which were developed by Quantum Technology (QT), are modified and developed in SPACE code. In particular, the fuel relocation limitation threshold parameter and the fuel power distribution during relocation are newly developed. The FFR models are also verified with simple known problems. The newly developed and implemented FFR models in SPACE are validated with calculations using Halden IFA-650 test data. The newly developed FFR model in SPACE can reasonably predict the fuel relocation and axial rod temperature distribution due to fuel mass redistribution. However, intensive validation tests including various conditions are necessary to validate the new FFR model in SPACE code.

Численное исследование полидисперсных двухфазных течений в осесимметричном сопле Лаваля с учетом силы Магнуса, действующей на вращающиеся капли

The available papers on two-phase flows in de Laval nozzles are focused on the effect of various initial conditions, models of coagulation, fragmentation, and rotation of droplets on their local and integral characteristics. Some papers note that due to the difference in the velocities of the gas and droplets along the nozzle axis, the Magnus force acts on the rotating droplets perpendicular to the specified difference and deflects the trajectories of the droplets toward the nozzle wall. In an earlier paper, the authors proposed a mathematical model of a two-phase flow in an axisymmetric de Laval nozzle that accounts for the Magnus force on the basis of the kinetic equation. The present article is devoted to a numerical study of a polydisperse two-phase flow in a de Laval nozzle with account for the coagulation, fragmentation, and rotation of droplets and the Magnus force. This study is based on the “monodisperse” model of fragments developed by I.M. Vasenin and A.A. Shreiber, the method of labeled drops (the Lagrange method), and the finite-difference schemes of second order accuracy. The calculations are carried out for a test nozzle configuration with condensate formation on the nozzle wall both with and without the Magnus force accounted. The calculated results show that the Magnus force has different impacts on the trajectories of droplets of various sizes. It should be noted that the limiting trajectories of the droplets approach the nozzle wall due to the Magnus force, resulting in the earlier dropout on the wall. Therefore, when designing the divergent section of the nozzle, it is necessary to consider the revealed approach of the location of the dropout, which is associated with the Magnus force, to the nozzle throat.

Genomic footprints of (pre) colonialism: Population declines in urban and forest túngara frogs coincident with historical human activity.

Urbanisation is rapidly altering ecosystems, leading to profound biodiversity loss. To mitigate these effects, we need a better understanding of how urbanisation impacts dispersal and reproduction. Two contrasting population demographic models have been proposed that predict that urbanisation either promotes (facilitation model) or constrains (fragmentation model) gene flow and genetic diversity. Which of these models prevails likely depends on the strength of selection on specific phenotypic traits that influence dispersal, survival, or reproduction. Here, we a priori examined the genomic impact of urbanisation on the Neotropical túngara frog (Engystomops pustulosus), a species known to adapt its reproductive traits to urban selective pressures. Using whole-genome resequencing for multiple urban and forest populations we examined genomic diversity, population connectivity and demographic history. Contrary to both the fragmentation and facilitation models, urban populations did not exhibit substantial changes in genomic diversity or differentiation compared with forest populations, and genomic variation was best explained by geographic distance rather than environmental factors. Adopting an a posteriori approach, we additionally found both urban and forest populations to have undergone population declines. The timing of these declines appears to coincide with extensive human activity around the Panama Canal during the last few centuries rather than recent urbanisation. Our study highlights the long-lasting legacy of past anthropogenic disturbances in the genome and the importance of considering the historical context in urban evolution studies as anthropogenic effects may be extensive and impact nonurban areas on both recent and older timescales.

Numerical modeling of clog fragmentation during SEN clogging in steel continuous casting

In the study of clogging during steel continuous casting, less attention was paid to the clog fragmentation, although it always accompanies the clogging process. This paper introduces a sub-model for the clog fragmentation integrated into a comprehensive transient clogging model. In this sub-model, the intricate network of the clog is simplified as a bunch of fictitious cylinders. Each cylinder, called ‘clog finger’, contains a column of spherical non-metallic inclusions (NMIs), which are mechanically bound by sintering at contact points. The mechanical stress acting at the sintering neck between NMIs due to hydraulic forces of the melt flow is evaluated. Simulation of clogging/fragmentation in a real-scale SEN was conducted using the integrated clogging model. Comparing the simulation results with the as-clogged SEN observed in steel plants revealed a qualitative agreement. The effects of different parameters were discussed. The importance of the fragmentation and necessity to have such a sub-model were affirmed.

The effect of oil-in-water emulsion pesticide on the evolution of liquid sheet rim disintegration and the spraying distribution

Oil-based emulsions often used as agricultural chemical formulations to control pests and weeds. The instability of emulsion spray is an important challenge. In this work, the effects of liquid sheet rim disintegration on spray angle and spraying distribution were studied by visualization method. The results show that the addition of emulsion change the way of rim disintegration and this change may be responsible for the improvement of spray angle and spraying distribution uniformity compared with water spray. In emulsion spray, the typical feature of rim disintegration is the asymmetric “half-moon” shaped holes, which leads to earlier disintegration at the edge of the liquid sheet. The hole coalescence at the rim of liquid sheet may be the reason for the increase of spray angle, because it divides the liquid sheet into small liquid masses and breaks the inward contraction trend of the cohesive attraction of liquid mass. Only 0.02% addition of emulsion, the spray angle could be increased by 8°, the typical liquid sheet breakup length (typical length) and the liquid sheet rim breakup length (rim length) from 23.297 mm to 18.609 mm reduce to 16.3 mm and 9.099 mm, and the spraying distribution curve become more uniform. In addition, the effects of spray structure on spraying distribution characteristics under different concentrations and spray pressures are also discussed. This study could provide a reference for the optimal use of pesticide formulations in the field, the reduction of pesticide waste and environmental pollution, and the establishment of atomization and fragmentation models.

A physical survey of meteoroid streams: Comparing cometary reservoirs

In this work, we present an optical survey of mm-sized meteoroids using the Canadian Automated Meteor Observatory’s (CAMO) mirror tracking system. The system tracks meteors to magnitude +7.5 through an image-intensified telescopic system which has a spatial accuracy of ∼1m and a temporal resolution of 10ms. We analyse 41 meteors from 13 showers with known parent bodies, recorded between 2016 and 2022. We fit a numerical ablation and fragmentation model to our data which models meteoroid fragmentation as erosion into 10µm to 500µm constituent grains and used the observed wake as a hard constraint on the model parameters. We measure average bulk meteoroid densities which are consistent with in situ measurements: 602 ±155kgm−3 for Jupiter-family and 345 ±48kgm−3 for Halley-type showers. The Geminids had the highest measured bulk density of 1387 ±240kgm−3, consistent with carbonaceous material. We fail to reproduce the high bulk density (>3000kgm−3) for Jupiter-family meteoroids previously reported in the literature derived using fragmentation models on data sets with fewer observational constraints. We also provide estimates of the meteoroid grain sizes, grain mass distributions, and energy necessary to trigger the erosion for meteoroids in the analysed showers.

Peridynamic modelling of dynamic damage and fragmentation of cracked solids during impact contact

Dynamics damage of solids exhibit unique characteristics that are absent in static analysis. The presence of pre-existing cracks further increases the complications. To address this issue, the present study focuses on modelling dynamic damage of cracked solids during impact contact. The model is formulated based on the state-based peridynamics. It incorporates a modified damage model and employs the short-range force approach to capture the impact damage. The damping force is introduced to eliminate numerical oscillation around cracks. Then, the adaptive explicit time integration is introduced to efficiently solve the peridynamic equations. Model performance is evaluated through benchmark tests. Next, we simulate impact between two spheres with pre-existing cracks. Our focus lies in comprehending the mechanisms by which material properties and crack patterns affect damage. Further sensitivity analysis reveals that the kinetic energy of the impact system is significantly affected by the pre-existing cracks and geometric parameters of the cracks, including their number, length, angle, and distribution. The interplay of crack interaction and the gradual connection of the damaged region plays a vital role in the phenomena. The presented study offers insights into damage evolution during impact contact and provides guidelines for assessing impact damage in structures with pre-existing defects.

Baryon correlations in Pythia

We present the results from our investigation of angular correlations between baryons pairs in the Pythia8 event generator. We show how colour reconnection models and hadronization mechanisms influence such angular correlations and in particular address the effect of gluons on the baryon production mechanism in the Lund string fragmentation model. We conclude by discussing the new theoretical ideas in comparison with the ALICE pp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ extrm{pp} $$\\end{document} collision results for the baryon angular correlations. We propose a hypothesis for suppressing baryons produced in gluon jets and show how that may influence the angular correlations.

Sleep fragmentation affects glymphatic system through the different expression of AQP4 in wild type and 5xFAD mouse models

AbstractBackgroundSleep is an important physiological process, during which extracellular metabolic wastes, such as amyloid and tau protein, are cleared via paravascular pathway. Changes in the timing and structure of sleep occur across the lifespan. Increased sleep fragmentation and reductions in slow wave sleep (SWS) represent the hallmark signs of age‐related changes in sleep. The origin of sleep disturbances in AD is thought to be multifactorial. In the aging brain, the impairment of glymphatic pathway function slows the clearance of interstitial Aβ, rendering the aging brain vulnerable to neurodegenerative disease. Several authors have independently shown that glymphatic flux depends upon the expression and perivascular localization of the astroglial water channel aquaporin‐4 (AQP4).MethodIn this study, we performed and validated a mouse model of AD and chronic sleep fragmentation, a sleep disorder that mimics more correctly a real condition of intermittent and continuous awakening. We analyzed the effect of sleep fragmentation in wild type and 5xFAD mice. All the animals underwent to behavioral studies to analyze anxiety and spatial and working memory. We had validated sleep fragmentation and its effect through EEG and biomolecular analysis, by observing all the macro‐areas implied in sleep regulation.ResultWe noticed that sleep fragmentation induces a general acceleration of AD progression in 5xFAD mice, while in wild type mice it affects cognitive behaviors in particular learning and memory. Both these events may be correlated to AQP4 modulation, a crucial player of the glymphatic system activity. In particular, sleep fragmentation differentially affects AQP4 expression according to the stage of the disease, with an up‐regulation in younger animals, while such change cannot be detected in older ones. Moreover, in wild type mice sleep fragmentation affects cognitive behaviors, in particular learning and memory, by compromising the glymphatic system through the decrease of AQP4.ConclusionNevertheless, an in‐depth study is needed to better understand the mechanism by which AQP4 is modulated and whether it could be considered a risk factor for the disease development in wild type mice. If our hypotheses are going to be confirmed, AQP4 modulation may represent the convergence point between AD and sleep disorder pathogenic mechanisms

FMDL: Federated Mutual Distillation Learning for Defending Backdoor Attacks

Federated learning is a distributed machine learning algorithm that enables collaborative training among multiple clients without sharing sensitive information. Unlike centralized learning, it emphasizes the distinctive benefits of safeguarding data privacy. However, two challenging issues, namely heterogeneity and backdoor attacks, pose severe challenges to standardizing federated learning algorithms. Data heterogeneity affects model accuracy, target heterogeneity fragments model applicability, and model heterogeneity compromises model individuality. Backdoor attacks inject trigger patterns into data to deceive the model during training, thereby undermining the performance of federated learning. In this work, we propose an advanced federated learning paradigm called Federated Mutual Distillation Learning (FMDL). FMDL allows clients to collaboratively train a global model while independently training their private models, subject to server requirements. Continuous bidirectional knowledge transfer is performed between local models and private models to achieve model personalization. FMDL utilizes the technique of attention distillation, conducting mutual distillation during the local update phase and fine-tuning on clean data subsets to effectively erase the backdoor triggers. Our experiments demonstrate that FMDL benefits clients from different data, tasks, and models, effectively defends against six types of backdoor attacks, and validates the effectiveness and efficiency of our proposed approach.

Data independent acquisition for gas chromatographic MS/MS analysis of volatile compounds

This study presents a novel tandem mass spectrometry (MS/MS) approach utilizing a data independent acquisition (DIA) concept specifically designed with gas chromatography−electron ionization−triple quadrupole mass spectrometry (GC−EI-QqQMS). This allows compound identification based on comparison between all the experimental MS/MS product ion spectra and the simulated library data of >1,000 MS/MS transitions of 71 compounds. The simulation data were generated by using the Competitive Fragmentation Modeling (CFM-ID) 3.0 program. The approach for calculation of the DIA MS/MS library match scores was then established and applied for identification of a range of terpenoids and oxygenated compounds in perfume. The identity of each peak was confirmed using 4–241 MS/MS transitions. The established data collection and analysis methods are expected to be useful for increased confidence in volatile compound analysis.

Simulation of In-Space Fragmentation Events

In the next years, the space debris population is expected to progressively grow due to in-space collisions and break-up events; in addition, anti-satellite tests can further affect the debris environment by generating large clouds of fragments. The simulation of these events allows identifying the main parameters affecting fragmentation and obtaining statistically accurate populations of generated debris, both above and below detection thresholds for ground-based observatories. Such information can be employed to improve current fragmentation models and to reproduce historical events to better understand their influence on the non-detectable space debris population. In addition, numerical simulation can also be used as input to identify the most critical objects to be removed to reduce the risk of irreversible orbit pollution. In this paper, the simulation of historical in-orbit fragmentation events is discussed and the generated debris populations are presented. The presented case-studies include the COSMOS-IRIDIUM collision, the COSMOS 1408 anti-satellite test, the 2022-151B CZ-6A in-orbit break-up, and a potential collision of ENVISAT with a spent rocket stage; for these events, results are presented in terms of cumulative fragments distributions and debris orbital distributions.

Network Optimization of Carbon Monoxide Sensor Nodes in the Metropolitan Region of São Paulo

Air pollution is one of the biggest problems affecting large urban areas. Better monitoring of regions suffering from this type of pollution is in the interest of public health. Although many cities employ sensors to monitor air pollution, a current concern is how to establish the ideal number of sensors to monitor a given geographical region. To address this concern, this research proposes a method to optimize the number of sensors in an air pollution monitoring network to cover a given region efficiently and precisely and uses the metropolitan region of São Paulo, Brazil, and CO sensors as an example. The model of Fragmentation into Groups via Routes is proposed to distribute sensors within micro-regions that display similar air pollution characteristics. A network of virtual sensors is created, and the output of each sensor is established using a method of spatial interpolation called IDW. To identify the optimum sensor configuration, a genetic algorithm is used to assess the topology with the lowest variance of data spread. A lesser number of sensor stations to be treated leads to faster responses to sudden changes in urban conditions. Therefore, municipality authorities can take quick measures to improve the population’s wellness.

Numerical modelling of rock fragmentation under high in-situ stresses and short-delay blast loading

Since the invention of electronic detonators with a delay accuracy within 1 ms, short-delay blasting technology has been used in mining and tunnelling engineering to improve rock fracturing and control blast-caused vibration. However, the fragmentation characteristics of pre-stressed rock under short-delay blast loading have not been studied in detail. In this study, the interaction between the short-delay blast loading and static in-situ stress is investigated using a FEM-based modelling method and image-processing approach. Firstly, single-hole blasting tests were conducted in an underground roadway with a burial depth of 620 m. Subsequently, a single-hole blasting model was developed in LS-DYNA and validated against one of the experimental results, a two-hole delay blasting model was established to simulate rock fracture and fragmentation under different delay times and in-situ stresses. Finally, the underlying mechanism of in-situ stress affecting the optimum delay time was theoretically analyzed and an analytical solution for optimum delay was proposed. The tested results show that under a borehole length and charge weight of 1 m and 1.5 kg, respectively, the average fragment size is approximately 10.5 cm, and the crater radius and depth are 0.67 m and 0.96 m, respectively. The numerical results indicate that both of average fragment size and fragment size distribution range significantly increase with the increase of in-situ stress, while they first decrease and then increase with the increase of short delay times. Moreover, there is a specific delay window ranging from 0.5 to 3 ms where short-delay blasting improves fragmentation performance, and the optimum delay time increases with the increase of in-situ stress. The findings of this study can aid in improving the efficiency and safety of blasting operations in deep hard rock mining.

Exploring a novel methodology for post impact assessments of chemical accidents on forest ecosystems: With damage, recovery, and resilience aspects of vegetation

Chemical accident leads to severe environmental problems, especially threatening the capacity of the ecosystem for ‘sustainability’. Therefore, a systematic response system, that includes performing a spatial and temporal assessment of the overall impacts due to chemical accidents, is urgently required. This study constructed a new methodology that can support the scientific implementation of post impact assessment through quantitatively assessing damaging impact and recovery endpoints for vegetation subjected to chemical accidents from both spatial and temporal aspects. Through applying a novel index ΔVI (Damage Assessment Factor), vegetation impact was quantitatively assessed. Afterward, with ΔVI applied as a chemical accident impact variable, MaxEnt was used for vegetation recovery assessment. With the change of potential habitat per each scenario, the recovery endpoint was quantitatively derived using the newly developed index, VRI (Vegetation Recovery Index). The results indicated a tendency of damaging impact to decline over time, with shortening of damage persistence and rapid recovery endpoints at a further distance from the accident site, by each spatial zone (R1-R5) in each distance range (0–1000 m). Further, vegetation resilience was analyzed based on the temporal difference between damaging impact and recovery tendency, using the newly developed index, VRCI (Vegetation Resilience Capacity Index). The forest that lacks diversity in functions·species compositions due to fragmentation and narrow areas showed low resilience, and it was spatially·quantitatively analyzed through the landscape fragmentation model (ArcGIS 10.3). This study is expected to be applied as a basis for implementing systematic post management and policies of vegetation in chemical accidents.

DETERMINATION OF OPTIMAL OBSERVATION NETWORK PARAMETERS FOR MAPPING PALEOCHANNEL BY THE ELECTRICAL RESISTIVITY TOMOGRAPHY METHOD BASED ON NUMERICAL AND PHYSICAL MODELING

Link for citation: Osipova P.S., Olenchenko V.V., Chekryzhov A.V. Determination of optimal observation network parameters for mapping paleochannel by the electrical resistivity tomography method based on numerical and physical modeling. Bulletin of the Tomsk Polytechnic University. Geo Аssets Engineering, 2023, vol. 334, no. 10, рр. 232-242. In Rus. The relevance of the study is explained by the need to determine the methodological features of applying the electrical resistivity tomography method to map paleochannels when prospecting for placer gold. The main aim: to determine the necessary and enough parameters of the observation network for paleochannel mapping based on numerical and physical modeling. Object: electrical fields on the physical and numerical model of the paleochannel. Methods: electrical resistivity tomography, physical experiment, numerical simulation. Results. Electrical soundings by electrical tomography were carried out on a physical model of a river valley. In addition, a numerical experiment was performed on a three-dimensional model of a river valley fragment with a paleochannel. The unit of the survey scale is the distance between two electrodes, which in the experiment is 1 cm and is equivalent to 5 m in real field studies. The distance between the profiles varied from 2 to 12 cm with a step of 2 cm, which corresponds to different survey scales. In accordance with geological concepts, the authors formed a model of a river valley with a segmentally gently stage of channel formation. Three-dimensional inversion was carried out for the data set obtained at the maximum density of the observation network, and then for the data sparse to the desired scale. On the resistivity map, the paleochannel is recognized by a ribbon-shaped high-resistivity anomaly. The analysis of the maps showed that to determine the shape of the paleochannel in plan, it is necessary to use the observation network scale of 1:3000, at which the distance between the profiles is 30 m. The physical experiment results were confirmed by mathematical modeling. The scale should be reduced to 1:5000 with detailing in individual areas to improve the economic efficiency of geophysical research.

First holistic modelling of meteoroid ablation and fragmentation: A case study of the Orionids recorded by the Canadian Automated Meteor Observatory

18 mm-sized Orionid meteoroids were captured in 2019 and 2020 by the Canadian Automated Observatory’s mirror tracking system. Meteor position measurements were made to an accuracy of ∼1m and the meteors were tracked to a limiting magnitude of about +7.5 at the faintest point. The trajectory estimation shows the intrinsic physical dispersion of the Orionid radiant is 0.400°±0.062°. An erosion-based entry model was fit to the observations to reproduce ablation and fragmentation for each meteor, simultaneously reproducing the light curve, the dynamics, and the wake. Wake observations were found to directly inform the grain mass distribution released in the modelled erosion. A new luminous efficiency model was derived from simultaneous radar and optical observations and applied in the modelling to improve its accuracy. The results show that the apparent strength of Orionids varies with radiant location and time of appearance during the period of shower activity. The average differential grain mass distribution index was 2.15, higher than found from in-situ estimates, possibly due to the evolution of the physical properties of meteoroids since ejection. All Orionids showed leading fragment morphology which was best explained by stopping the erosion at the peak of the light curve, leaving a non-fragmenting meteoroid with ∼10% of the original mass. The inverted Orionid meteoroid average bulk density of ∼300kgm−3, corresponding to porosities of ∼90%, is consistent with in-situ measurements of larger dust particles by Vega-2 at 1P/Halley and Rosetta at 67P.

Programmable and Reversible Integrin-Mediated Cell Adhesion Reveals Hysteresis in Actin Kinetics that Alters Subsequent Mechanotransduction.

Dynamically evolving adhesions between cells and extracellular matrix (ECM) transmit time-varying signals that control cytoskeletal dynamics and cell fate. Dynamic cell adhesion and ECM stiffness regulate cellular mechanosensing cooperatively, but it has not previously been possible to characterize their individual effects because of challenges with controlling these factors independently. Therefore, a DNA-driven molecular system is developed wherein the integrin-binding ligand RGD can be reversibly presented and removed to achieve cyclic cell attachment/detachment on substrates of defined stiffness. Using this culture system, it is discovered that cyclic adhesion accelerates F-actin kinetics and nuclear mechanosensing in human mesenchymal stem cells (hMSCs), with the result that hysteresis can completely change how hMSCs transduce ECM stiffness. Results are dramatically different from well-known results for mechanotransduction on static substrates, but are consistent with a mathematical model of F-actin fragments retaining structure following loss of integrin ligation and participating in subsequent repolymerization. These findings suggest that cyclic integrin-mediated adhesion alters the mechanosensing of ECM stiffness by hMSCs through transient, hysteretic memory that is stored in F-actin.