Dynamic Fragmentation Research Articles

Accurate prediction of dynamic protein-ligand binding using P-score ranking.

Protein-ligand binding prediction typically relies on docking methodologies and associated scoring functions to propose the binding mode of a ligand in a biological target. Significant challenges are associated with this approach, including the flexibility of the protein-ligand system, solvent-mediated interactions, and associated entropy changes. In addition, scoring functions are only weakly accurate due to the short time required for calculating enthalpic and entropic binding interactions. The workflow described here attempts to address these limitations by combining supervised molecular dynamics with dynamical averaging quantum mechanics fragment molecular orbital. This combination significantly increased the ability to predict the experimental binding structure of protein-ligand complexes independent from the starting position of the ligands or the binding site conformation. We found that the predictive power could be enhanced by combining the residence time and interaction energies as descriptors in a novel scoring function named the P-score. This is illustrated using six different protein-ligand targets as case studies.

Research on Dynamic Graphic Features in Digital Media Interfaces

In digital media interfaces, dynamic graphics integrate elements of animation design, graphic design, andcinematic language, presenting in various forms and demonstrating significant inclusivity. From the perspective of visual cognition, by capturing dynamic graphics within the interface, three-dimensional information such as time and space is acquired, and the cognition process exhibits characteristics of spatial and temporal correlation. In terms of information cognition, dynamic representation fragments information, resulting in a sense of discontinuity and intermittent memory. The efficiency of information cognition and transmission is enhanced through the coordination of audio, video, and other elements. In aesthetic perception, with the rise of Internet culture, people’s aesthetic perceptions towards dynamic graphic design have evolved, showcasing a generalization of form and the instantaneous nature of content. Technically, the complexity of design and the diversity of applications have established dynamic graphics as a typical design style label in digital media interfaces.

Visualization study on flash boiling spray characteristics of high-pressure liquid ammonia with different nozzle diameters

Zero-carbon fuel liquid ammonia is prone to flash boiling under actual engine conditions. However, the influence rule of liquid ammonia flash boiling spray characteristics under different nozzle diameters remains unclear. Therefore, the macroscopic and microscopic flash boiling spray characteristics were investigated by utilizing long focal length high-speed shadowgraphy and long working distance microscopic high-speed shadowgraphy methods. Three nozzle diameters are 0.12 mm, 0.32 mm, and 0.52 mm. The results indicate that the nozzle diameters exhibit stage variation effects on the peak spray cone angle in different flash boiling stages. In the flare flash boiling stage, the peak cone angle is controlled by the degree of superheat and decreases with increasing nozzle diameter; In the transition/critical flash boiling stage, the peak cone angle is regulated by ambient pressure and increases with nozzle diameter. Furthermore, introducing coefficient fitting using Oh and Ja, representing dynamic and thermodynamic fragmentation, reveals that the peak cone angle is slightly more influenced by Oh than Ja. The time-averaged Sauter Mean Diameter increases with nozzle diameter, and the growth rate of the average Sauter Mean Diameter between adjacent diameters is 5 %–10 % in the flare flash boiling stage, 5 %–15 % in the transition flash boiling stage, and 15 %–35 % in the critical flash boiling stage. The most probable droplet diameters do not exhibit a monotonic increase with nozzle diameter but show a significant increase in the distribution of large droplets. Considering the comprehensive evaluation of macroscopic and microscopic tests, the 0.32 mm nozzle diameter exhibits the optimal liquid ammonia spray characteristics in this study.

The minimum mass for star formation by dynamical fragmentation: dependence on epoch, dust abundance, and environment

ABSTRACT We estimate the minimum mass of a star formed by dynamical collapse and fragmentation, as a function of epoch, dust abundance, and environment. Epoch is parametrized by redshift, zred, through the variation in the temperature of the cosmic microwave background. The dust abundance is parametrized by the mass-fraction in dust, ZD, with the additional simplifying assumption that the intrinsic properties of dust do not change with ZD, only the amount of dust. Environment is parametrized by the energy-density of the ambient suprathermal radiation fields through a dilution factor ω⋆ (applied to a blackbody radiation field at $T_{\star }=10^4\, {\rm K}$). The critical condition is that a spherical proto-fragment should be able to cool, and therefore contract, fast enough to detach from neighbouring proto-fragments. The minimum mass increases with increasing redshift, increasing dust abundance, and increasing suprathermal background. Values in the range from $M_{{\rm MIN}}\sim 0.002\, {\rm M}_{\odot }$ to $M_{{\rm MIN}}\sim 0.2\, {\rm M}_{\odot }$ are obtained at the extremes of the parameter ranges we have considered (0 ≤ zred ≤ 8, 0.00016 < ZD < 0.04, and 10−15 ≤ ω⋆ ≤ 10−8). Our results agree quite well with the predictions of detailed numerical simulations invoking similar redshifts and dust abundances, but our estimates are somewhat lower; we attribute this difference to resolution issues and the small-number statistics from the simulations. The increased minimum masses predicted at high redshift and/or high suprathermal background result in significantly bottom-light initial mass functions, and therefore low mass-to-light ratios, provided that the dust abundance is not too low. The changes due to high suprathermal background may be particularly important for star formation in galactic nuclei and at high redshift.

An approach to distinguish chemical and kinetic energy of reactive materials: PTFE/LiF as an inert substitute to PTFE/Al

AbstractTo distinguish between the kinetic and chemical contributions in the impact of PTFE/Al, this study explores the feasibility of introducing an inert substitute for PTFE/Al by substituting aluminum (Al) with inert materials. Three specimens were fabricated through a process involving mixing, compression, and sintering of raw materials The mechanical properties of these specimens were assessed. Dynamic fragmentation tests of PTFE/Al and PTFE/LiF specimens were performed. These results further substantiate the potential of PTFE/LiF as an inert alternative to PTFE/Al, the two materials exhibit comparable fragmentation distribution characteristics. A preliminary exploration of the energy release in both materials was conducted via vented chamber calorimetry tests. The findings reveal that, at an impact velocity of roughly 650 m/s, only 66.9 % of the materials were deposited into the chamber, with a mere 17.8 % being initiated, about 88.9 % of the total deposited energy results from the chemical reaction energy within the PTFE/Al materials. Importantly, this method demonstrates promise for further application in energy release analysis experiments for various PTFE/Al‐based reactive materials. These findings are beneficial for evaluating the energy release characteristics of reactive fragments on typical targets and lay the foundation for refining energy release models of such materials in future research.

Modeling the dynamic fracture of concrete — A robust, efficient, and accurate mesoscale description

Dynamic loading of concrete often leads to excessive cracking and fragmentation. Since these processes are massively influenced by the underlying heterogeneity of the material, discrete modeling of the lower-scale features strongly improves the simulation results. At the same time, the computational effort is greatly increased. We therefore propose here a mesomechanical simulation approach which is efficient in terms of model generation and computational efforts even for large 3d models. Furthermore, it is robust by limiting the application of computationally less efficient cohesive zone elements to the weak transition boundary between matrix and inclusions. Intermatrix failure is considered by a smeared crack approach and element removal after a certain crack opening has been reached. We apply an improved version of the widely used RHT concrete model, which is enhanced with a principal stress criterion. The resulting approach leads to an accurate replication of experiments in terms of crack propagation and stress wave induced dynamic fragmentation.

Insights and mechanics-driven modeling of human cutaneous impact injuries

Cutaneous damage mechanisms related to dynamic fragment impacts are dependent on the impact angle, impact energy, and fragment characteristics including shape, volume, contact friction, and orientation. Understanding the cutaneous injury mechanism and its relationship to the fragment parameters is lacking compromising damage classification, treatment, and protection. Here we develop a high-fidelity dynamic mechanics-driven model for partial-thickness skin injuries and demonstrate the influence of fragment parameters on the injury mechanism and damage sequence. The model quantitatively predicts the wound shape, area, and depth into the skin layers for selected impact angles, kinetic energy density, and the fragment projectile type including shape and material. The detailed sequence of impact damage including epidermal tearing that occurs ahead of the fragments initial contact location, subsequent stripping of the epidermal/dermal junction, and crushing of the underlying dermis are revealed. We demonstrate that the fragment contact friction with skin plays a key role in redistributing impact energy affecting the extent of epidermal tearing and dermal crushing. Furthermore, projectile edges markedly affect injury severity dependent on the orientation of the edge during initial impact. The model provides a quantitative framework for understanding the detailed mechanisms of cutaneous damage and a basis for the design of protective equipment.

Rapid geometric characterization of ceramics fragments through split Hopkinson pressure bar tests

AbstractThe research on fracture mechanisms of brittle materials is extremely difficult such as the determination of the energy absorption modes and the geometric characteristics of debris. In this paper, a dynamic experimental fragment recovery device was developed to study the facture characteristics of A99 ceramics (the mass of Al2O3 accounts for 99%) based on the Split‐Hopkinson pressure bar (SHPB) experiments, in which the energy absorption mechanism was revealed. A three‐view characterization method was developed to obtain the geometric characterization formula under various strain rate; therefore, the geometric parameters of the fragments can be quickly characterized. The failure mode was investigated in correlation between strain rate and micro‐cracks. It was found that the shape of the strain rate controlled the proportion of dissipated energy. At a lower strain rate the fragment was prone to needle shape, while at a higher strain rate (above 2001 s−1) the proportion of dissipated energy increased to 72% and the fragment shape tended to be nearly spherical. A formula based on strain rate was proposed to characterize the geometric parameters of the fragments without the need of geometry dimensions; therefore, the fragment rate can be quickly obtained, which could provide guidance for the design of ceramics parts.

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.

Aging trajectory and end-of-life prediction for lithium-ion battery via similar fragment extraction of capacity degradation curves

Considering the limitations on future general deterioration trend description and local capacity regeneration capture of existing methods, this paper designs a novel aging trajectory and end-of-life (EOL) prediction method for lithium-ion battery via similar fragment extraction of capacity degradation curves. The proposed method attempts to make the following three contributions: 1) By fusion of particle filter (PF)-based general deterioration trend description and similar fragment extraction-based local capacity regeneration capture, the developed method can achieve accurate aging trajectory and EOL prediction. 2) Considering the similarity in degradation paths, a novel dynamic time warping-based similar fragment extraction method is proposed to learn the deterioration path from the same type batteries' limited capacity degradation curves. 3) On the basis of the predicted future capacity, the PF-based capacity empiric degradation model can be iteratively updated to accurately reflect battery future general deterioration trend. The validation results based on Beijing Institute of Technology dataset demonstrate that the maximum mean absolute error and root mean squared error of predicted aging trajectory, and the maximum value of absolute relative error between reference and predicted EOL achieved by the developed method with the help of the same type of battery's limited capacity degradation curves are only 1.09%, 1.28% and 3.23%, respectively.

Modeling of space debris fragment restoring technologies in the non-redundant array of aperture synthesis

The problem of monitoring space debris (SD) of anthropogenic origin is discussed to ensure the safety of near-Earth space environment exploration. For dynamic low-orbit SD fragments, acquisition and processing technologies of short-exposure image series, obtained in a non-redundant aperture synthesis array, are proposed and investigated. Specific features of the optical transfer function (OTF) of the non-redundant array, namely, its "insular" character, lead to difficulties in restoring the spatial spectrum of the control object, undistorted by the atmosphere, in the whole spatial-frequency domain of the array. It is shown that to restore the object's spatial spectrum module, undistorted by the atmosphere, in the whole spatial frequency domain of the array, it is necessary to use algorithm of the Labeyrie method, modified by the authors of the present work. To restore the phase of the spatial spectrum, it is necessary to use the algorithms of unfolding the closed phase equations of the triple correlations method. By physical modeling of the formation and registration processes of analog images in the atmosphere-array system and subsequent statistical processing of digitized images, experimental evidence is given of the effectiveness of the proposed restoring technologies to achieve high resolution of SD fragments in the array, aimed at their subsequent identification and removal. Recommendations are given for practical implementation of the considered promising construction and application technologies of optical systems to control SD fragments.

Dynamic Analysis of a Long Run-Out Rockslide Considering Dynamic Fragmentation Behavior in Jichang Town: Insights from the Three-Dimensional Coupled Finite-Discrete Element Method

To clearly realize the dynamic process as well as the dynamic fragmentation behavior of a long run-out rockslide, a novel numerical method for landslide simulation of the coupled finite-discrete element method (FDEM) was applied and the Jichang rockslide was used as a case. The calibrated simulation result of the FDEM in a rockslide deposit corresponds well with the real rockslide deposit. The main run-out process of the rockslide lasts for 75 s and can be divided into acceleration and deceleration stages, which last for 33 s and 42 s, respectively. The maximum overall rockslide movement speed is 35 m/s while the partial sliding mass reaches 45 m/s. The fracturing, fragmentation, and disintegration processes of the sliding mass can be clearly observed from the dynamic scenarios. Fracture energy generated by rock fracturing constantly increases with time in a non-linear form. Of the total fracture energy, 54% is released in the initial 5 s because of fracturing, and 39% of the total fracture energy is released because of fragmentation and disintegration in the last 35 s. The accumulated friction energy increases in the whole run-out process, and its magnitude is much greater than the kinetic energy and fracture energy of the sliding mass.

Cloud atlas: navigating the multiphase landscape of tempestuous galactic winds

ABSTRACT Galaxies comprise intricate networks of interdependent processes which together govern their evolution. Central among these are the multiplicity of feedback channels, which remain incompletely understood. One outstanding problem is the understanding and modelling of the multiphase nature of galactic winds, which play a crucial role in galaxy formation and evolution. We present the results of three-dimensional magnetohydrodynamical simulations of tall–box interstellar medium (ISM) patches with clustered supernova-driven outflows. Dynamical fragmentation of the ISM during superbubble breakout seeds the resulting hot outflow with a population of cool clouds. We focus on analyzing and modelling the origin and properties of these clouds. Their presence induces large-scale turbulence, which, in turn, leads to complex cloud morphologies. Cloud sizes are well described by a power-law distribution and mass growth rates can be modelled using turbulent radiative mixing layer theory. Turbulence provides significant pressure support in the clouds, while magnetic fields only play a minor role. We conclude that many of the physical insights and analytic scalings derived from idealized small-scale simulations of turbulent radiative mixing layers and cloud–wind interactions are directly translatable and applicable to these larger scale cloud populations. This opens the door to developing effective subgrid recipes for their inclusion in global-scale galaxy models where they are unresolved.

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.

Block‐Grain Phase Transition in Rock Avalanches: Insights From Large‐Scale Experiments

AbstractKnowledge of the processes and effects of the block‐grain phase transition in a fragmented system is essential for investigating rock avalanches. Several series of experiments are performed with a very large apparatus, using a jointed block, simulated by an assembly of packed breakable subblocks varying in configuration, as an analog for brittle rock. The analog jointed block is released from a hopper, moves on two inclined flumes with different slopes, and finally deposits on a horizontal platform. The block‐grain phase transition occurs, caused by subblock collisions and explosive impacts with the flume bottom. The dynamic behavior, seismic signal, fragment characteristic, and deposit structure of the analog material are determined. Our results demonstrate that fragmentation influences energy dissipation and momentum transfer, as well as subsequent flow and emplacement processes. A nonunified and piecewise relationship between the fragmentation degree and friction coefficients is observed. We ascribe this nonunified relationship to the varying dynamics and runout regimes that different configurations of jointed blocks undergo. The positive or negative feedback on energy generated by fragmentation is closely associated with the energy budget involved in this fragmented system, which depends substantively on the block configuration. Particularly, for flatter or larger jointed blocks, despite increased fragmentation absorbing the available energy for runout, it simultaneously changes the runout regime toward a more energy‐efficient one, thus instigating positive feedback. Our study further highlights the contribution of post‐fragmentation granular flow to the energy system.

Macro, meso, micro and nanoplastics in horticultural soils in Argentina: Abundance, size distribution and fragmentation mechanism

Soil contamination with plastics is a major worldwide concern. However, data on plastic pollution in horticultural soils from Latin America is scarce. Furthermore, there is limited information on the fragmentation process that plastics undergo in environmental conditions. In this study, we investigated the abundance of macro, meso, micro and nano plastics in a previously studied horticultural soil (2015) from Buenos Aires, that has not been used for any productive activity since. Although the mass of macroplastics was conserved, the number of plastic fragments per square meter increased significantly, indicating a possible natural fragmentation process. Black polyethylene (PE) mulch film was the most abundant plastic found. For this material, when considering the mass of plastic fragments per square meter, the relative abundance was, in decreasing order: macroplastics (65.1–79.1 %) > mesoplastics (15.6–24.8 %) > microplastics (5.3–12.4 %) > nanoplastics (0.1 %). However, when considering the number of plastic items per square meter, the order was: microplastics (2383–3815) > mesoplastics (1019–1076) > nanoplastics (509–550) > macroplastics (25–46). The size distribution of plastic debris was analyzed using the natural logarithm of abundance versus the square root of the mean decile area, with good linear correlations (0.7749 < R2 < 0.9785). These results provide evidence for an ongoing dynamic fragmentation process (Mott model). We hypothesize that the breakdown of plastic into smaller pieces could be explained by a random fragmentation process based on soil volume changes between natural hydration/dehydration states. These data suggest that soil under natural conditions could act as an ‘environmental plastic grinder’.

Monoisotopic targets production from atomic and molecular positive ion implantation in a tandem accelerator at low energies

We produced monoisotopic targets of 13C and 28,29Si with 1015−16 atoms/cm2 areal density by ion implantation in different matrices at the Accelerator Mass Spectrometry (AMS) facility in Mexico. The tandem accelerator terminal voltage was set at the lowest achievable value (200 kV) that yield beams with energy of 435 keV. It is possible to do ion implantation at lower energies in our facility through the use of molecular beams, so in this work we looked for, and successfully found, bound positively charged molecular beams, although with very low intensity. We inject 235 keV molecules into the charge of exchange canal (argon) of our tandem accelerator and detected the survival fraction of C2,3,4 molecules in 1+ and 2+ charge states or above. Our results showed that some molecules remain bound, with one or more electrons missing, after being forced through a low density gas stripper at relatively high energy. In the production process of negative molecular fluxes in the Source of Negative Ions by Cesium Sputtering (SNICS) we found an odd-even effect in their intensity that we understand as the coupling between the fragment size distribution of a dynamic fragmentation of graphite by cesium impact and the electron affinity of the molecules with n-carbon atoms. The availability of these kind of high energy molecular beams opens the door for discovery both in the study of the physics of negative and positive molecular ions.

A hybrid dynamic aggregation and fragmentation cognitive channel allocation model for mobile communication

A hybrid dynamic aggregation and fragmentation cognitive channel allocation model for mobile communication

Study on dynamic response characteristics of impact of freeze-thaw saturated marble in plateau area.

To study the effects that the perennial freeze-thaw environment exerts on the dynamic mechanical properties of marble, which characterizes the Qinghai-Tibet Plateau, impact tests were conducted, and saturated marble was utilized; thus, we analyzed the effect of different loading rates on its dynamic compressive strength, fragmentation pattern, and energy-absorbing density. The results indicate the following: (1) When 42.02s-1 ≤[Formula: see text]≤ 49.20s-1, the degree of fragmentation and the fractal dimension of saturated state marble is greater than that of the dry state marble; when [Formula: see text]<42.02s-1 or [Formula: see text]>49.20s-1, the dry state marble exhibits greater fragmentation than the saturated marble; (2) When the saturated state marble is subjected to a specific fractal dimension, the energy-absorbing density of the marble that characterizes the saturated state is great compared with the dry state, and when the fractal dimension increases, the energy-absorbing densities that characterize the two states gradually converge. (3) The effect of water on the mechanical properties of marble has an obvious rate dependence, showing a weakening effect at low strain rates and a strengthening effect at high strain rates. In regard to the analysis pertaining to the dynamic fracture mechanism of marble under the influence of the freeze-thaw environment that characterizes the plateau, the aforementioned experimental results exhibit considerable significance.

Modelling and mechanical characteristics of PDC cutter-rock interaction by combining mixed fragmentation modes with dynamic rock strength

Polycrystalline diamond compact (PDC) bit is one of the most widely used drill bits for improving the rate of penetration in deep oil and gas well and geothermal well. However, the dynamic rock fragmentation mechanics characteristics of PDC bits are still unclearly. A coupled fragmentation mechanics model of PDC cutter-rock interaction is established by combining the mixed fragmentation modes with dynamic strength. The coupling influence laws of cutter angle, cutting depth, dynamic strength ratio, breaking modes on the horizontal force coefficient (HFC), vertical force coefficient (VFC) and specific energy are analyzed. The model of this paper can optimize cutter inclination angle, cutting depth and minimum specific energy. With the increase of the cutter inclination angle, the dynamic VFC changes into two modes. The definition of the dynamic modes depends on the dynamic strength ratio. As the cutting angle increases, the cutting force increases. The cutting force increases nonlinearly with increasing cutting depth. The specific energy of rock fragmentation increases nonlinearly with increasing cutting depth. With the increase of dynamic strength, the specific energy of rock fragmentation increases nonlinearly. When the input-energy increases, the rate of penetration response is divided into three stages. The results have important guiding significance for the PDC bit design and drilling parameters optimization to increase the rate of penetration and the efficiency of exploration and development.