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1
Almerol, Jenny Lynn Ongue, and Marissa Pastor Liponhay. "Clustering of fast gyrotactic particles in low-Reynolds-number flow." PLOS ONE 17, no. 4 (April 7, 2022): e0266611. http://dx.doi.org/10.1371/journal.pone.0266611.
Анотація:
Systems of particles in turbulent flows exhibit clustering where particles form patches in certain regions of space. Previous studies have shown that motile particles accumulate inside the vortices and in downwelling regions, while light and heavy non-motile particles accumulate inside and outside the vortices, respectively. While strong clustering is generated in regions of high vorticity, clustering of motile particles is still observed in fluid flows where vortices are short-lived. In this study, we investigate the clustering of fast swimming particles in a low-Reynolds-number turbulent flow and characterize the probability distributions of particle speed and acceleration and their influence on particle clustering. We simulate gyrotactic swimming particles in a cubic system with homogeneous and isotropic turbulent flow. Here, the swimming velocity explored is relatively faster than what has been explored in other reports. The fluid flow is produced by conducting a direct numerical simulation of the Navier-Stokes equation. In contrast with the previous results, our results show that swimming particles can accumulate outside the vortices, and clustering is dictated by the swimming number and is invariant with the stability number. We have also found that highly clustered particles are sufficiently characterized by their acceleration, where the increase in the acceleration frequency distribution of the most clustered particles suggests a direct influence of acceleration on clustering. Furthermore, the acceleration of the most clustered particles resides in acceleration values where a cross-over in the acceleration PDFs are observed, an indicator that particle acceleration generates clustering. Our findings on motile particles clustering can be applied to understanding the behavior of faster natural or artificial swimmers.
2
Liang, Yongshi, Cliff Y. Guo, Xianglong Zhao, Qiang Qin, Yi Cheng, and Lixin He. "CPFD simulation on particle behaviour in an entrained-flow gasifier." Clean Energy 4, no. 1 (February 4, 2020): 75–84. http://dx.doi.org/10.1093/ce/zkz032.
Анотація:
Abstract A computational particle fluid dynamics simulation model for entrained-flow gasification was established in this study. The simulation results agree with the experimental data. The detailed particle information and residence-time distribution were obtained by injecting particle tracers in the simulation. The results show that the particles in the gasifier can be classified into three flowing zones, i.e. a fast-flowing zone, a recirculation zone and a spreading zone. The criterion for this classification was also provided. The rapid gas expansion caused by the fast reactions plays a significant role in forming the particle stream into these three zones. It accelerates the particles in the centre of the gasifier while pushing the particles near the expansion edge into the gas recirculation. Also, the concentrated oxygen distribution in the gasifier results in the formation of high- and low-temperature regions. The particles in the fast-flowing zone flow directly through the high-temperature region and most of these particles in this zone were fully reacted with a short residence time. Since particles in the recirculation zone are in a relatively low-temperature region, most of these particles are not fully gasified, although with a long residence time. The rest of particles in the spreading zone show moderate properties between the above two zones.
3
Tully, Christopher G. "Fast timing for collider detectors." International Journal of Modern Physics A 31, no. 33 (November 22, 2016): 1644022. http://dx.doi.org/10.1142/s0217751x1644022x.
Анотація:
Advancements in fast timing particle detectors have opened up new possibilities to design [Formula: see text] collider detectors that fully reconstruct and separate event vertices and individual particles in the time domain. The applications of these techniques are considered for the physics at CEPC.
4
Fiore, Andrew M., and James W. Swan. "Fast Stokesian dynamics." Journal of Fluid Mechanics 878 (September 17, 2019): 544–97. http://dx.doi.org/10.1017/jfm.2019.640.
Анотація:
We present a new method for large scale dynamic simulation of colloidal particles with hydrodynamic interactions and Brownian forces, which we call fast Stokesian dynamics (FSD). The approach for modelling the hydrodynamic interactions between particles is based on the Stokesian dynamics (SD) algorithm (J. Fluid Mech., vol. 448, 2001, pp. 115–146), which decomposes the interactions into near-field (short-ranged, pairwise additive and diverging) and far-field (long-ranged many-body) contributions. In FSD, the standard system of linear equations for SD is reformulated using a single saddle point matrix. We show that this reformulation is generalizable to a host of particular simulation methods enabling the self-consistent inclusion of a wide range of constraints, geometries and physics in the SD simulation scheme. Importantly for fast, large scale simulations, we show that the saddle point equation is solved very efficiently by iterative methods for which novel preconditioners are derived. In contrast to existing approaches to accelerating SD algorithms, the FSD algorithm avoids explicit inversion of ill-conditioned hydrodynamic operators without adequate preconditioning, which drastically reduces computation time. Furthermore, the FSD formulation is combined with advanced sampling techniques in order to rapidly generate the stochastic forces required for Brownian motion. Specifically, we adopt the standard approach of decomposing the stochastic forces into near-field and far-field parts. The near-field Brownian force is readily computed using an iterative Krylov subspace method, for which a novel preconditioner is developed, while the far-field Brownian force is efficiently computed by linearly transforming those forces into a fluctuating velocity field, computed easily using the positively split Ewald approach (J. Chem. Phys., vol. 146, 2017, 124116). The resultant effect of this field on the particle motion is determined through solution of a system of linear equations using the same saddle point matrix used for deterministic calculations. Thus, this calculation is also very efficient. Additionally, application of the saddle point formulation to develop high-resolution hydrodynamic models from constrained collections of particles (similar to the immersed boundary method) is demonstrated and the convergence of such models is discussed in detail. Finally, an optimized graphics processing unit implementation of FSD for mono-disperse spherical particles is used to demonstrated performance and accuracy of dynamic simulations of $O(10^{5})$ particles, and an open source plugin for the HOOMD-blue suite of molecular dynamics software is included in the supplementary material.
5
Yu, X. Y., J. P. Cowin, M. J. Iedema, and H. Ali. "Fast time-resolved aerosol collector: proof of concept." Atmospheric Measurement Techniques Discussions 3, no. 3 (June 1, 2010): 2515–34. http://dx.doi.org/10.5194/amtd-3-2515-2010.
Анотація:
Abstract. Atmospheric particles can be collected in the field on substrates for subsequent laboratory analysis via chemically sensitive single particle methods such as scanning electron microscopy with energy dispersive x-ray analysis. With moving substrates time resolution of seconds to minutes can be achieved. In this paper, we demonstrate how to increase the time resolution when collecting particles on a substrate to a few milliseconds to provide real-time information. Our fast time-resolved aerosol collector ("Fast-TRAC") microscopically observes the particle collection on a substrate and records an on-line video. Particle arrivals are resolved to within a single frame (4–17 ms in this setup), and the spatial locations are matched to the subsequent single particle analysis. This approach also provides in-situ information on particle size and number concentration. Applications are expected in airborne studies of cloud microstructure, pollution plumes, and surface long-term monitoring.
6
Yu, X. Y., J. P. Cowin, M. J. Iedema, and H. Ali. "Fast time-resolved aerosol collector: proof of concept." Atmospheric Measurement Techniques 3, no. 5 (October 12, 2010): 1377–84. http://dx.doi.org/10.5194/amt-3-1377-2010.
Анотація:
Abstract. Atmospheric particles can be collected in the field on substrates for subsequent laboratory analysis via chemically sensitive single particle methods such as scanning electron microscopy with energy dispersive x-ray analysis. With moving substrates time resolution of seconds to minutes can be achieved. In this paper, we demonstrate how to increase the time resolution when collecting particles on a substrate to a few milliseconds to provide real-time information. Our fast time-resolved aerosol collector ("Fast-TRAC") microscopically observes the particle collection on a substrate and records an on-line video. Particle arrivals are resolved to within a single frame (4–17 ms in this setup), and the spatial locations are matched to the subsequent single particle analysis. This approach also provides in-situ information on particle size and number concentration. Applications are expected in airborne studies of cloud microstructure, pollution plumes, and surface long-term monitoring.
7
Liu, Jinxian, Ye Chen, Bingbing Ni, Wei Ren, Zhenbo Yu, and Xiaoyang Huang. "Fast Fluid Simulation via Dynamic Multi-Scale Gridding." Proceedings of the AAAI Conference on Artificial Intelligence 37, no. 2 (June 26, 2023): 1675–82. http://dx.doi.org/10.1609/aaai.v37i2.25255.
Анотація:
Recent works on learning-based frameworks for Lagrangian (i.e., particle-based) fluid simulation, though bypassing iterative pressure projection via efficient convolution operators, are still time-consuming due to excessive amount of particles. To address this challenge, we propose a dynamic multi-scale gridding method to reduce the magnitude of elements that have to be processed, by observing repeated particle motion patterns within certain consistent regions. Specifically, we hierarchically generate multi-scale micelles in Euclidean space by grouping particles that share similar motion patterns/characteristics based on super-light motion and scale estimation modules. With little internal motion variation, each micelle is modeled as a single rigid body with convolution only applied to a single representative particle. In addition, a distance-based interpolation is conducted to propagate relative motion message among micelles. With our efficient design, the network produces high visual fidelity fluid simulations with the inference time to be only 4.24 ms/frame (with 6K fluid particles), hence enables real-time human-computer interaction and animation. Experimental results on multiple datasets show that our work achieves great simulation acceleration with negligible prediction error increase.
8
Liu, De-Ling. "Evaluating Aerosol Aspiration Efficiency in Fast-moving Air." Journal of the IEST 56, no. 2 (October 1, 2013): 20–28. http://dx.doi.org/10.17764/jiet.56.2.5600210764m14370.
Анотація:
Sampling representative aerosol particles in fast-moving air is a challenging task. Aerosols are significantly more massive than gas molecules, thus they might not follow air streamlines well and could be more easily subjected to sampling errors. This work examines the physical factors that govern the aspiration efficiency of an aerosol sampling probe in unidirectional moving air, and explores the plausible sampling deviations under various high air velocity scenarios. The particle sizes of 0.5 and 5 μm are of particular interest due to their use in defining air cleanliness levels in ISO 14644-1[1] and FED-STD-209.[2]* Our analytical results indicate that significant sampling errors could occur for 5-μm particles when a thick-walled sampling probe is used, or when the air velocity at the sampling probe inlet does not match the velocity of the incoming air (i.e., anisokinetic sampling). The aspiration efficiency of 0.5-μm particles, on the other hand, is nearly 100% due to sufficiently small inertia of these particles.
9
WU, JIAWEN, FENGQUAN ZHANG, and XUKUN SHEN. "GPU-BASED FLUID SIMULATION WITH FAST COLLISION DETECTION ON BOUNDARIES." International Journal of Modeling, Simulation, and Scientific Computing 03, no. 01 (March 2012): 1240003. http://dx.doi.org/10.1142/s179396231240003x.
Анотація:
In this paper, we present a method for fluid simulation based on smoothed particle hydrodynamic (SPH) with fast collision detection on boundaries on GPU. The major goal of our algorithm is to get a fast SPH simulation and rendering on GPU. Additionally, our algorithm has the following three features: At first, to make the SPH method GPU-friendly, we introduce a spatial hash method for neighbor search. After sorting the particles based on their grid index, neighbor search can be done quickly on GPU. Second, we propose a fast particle-boundary collision detection method. By precomputing the distance field of scene boundaries, collision detection's computing cost arrived as O(n), which is much faster than the traditional way. Third, we propose a pipeline with fine-detail surface reconstruction, and progressive photon mapping working on GPU. We experiment our algorithm on different situations and particle numbers of scenes, and find out that our method gets good results. Our experimental data shows that we can simulate 100K particles, and up to 1000K particles scene at a rate of approximately 2 times per second.
10
Zhang, Hao, Lorenzo Sironi, and Dimitrios Giannios. "Fast Particle Acceleration in Three-dimensional Relativistic Reconnection." Astrophysical Journal 922, no. 2 (December 1, 2021): 261. http://dx.doi.org/10.3847/1538-4357/ac2e08.
Анотація:
Abstract Magnetic reconnection is invoked as one of the primary mechanisms to produce energetic particles. We employ large-scale 3D particle-in-cell simulations of reconnection in magnetically dominated (σ = 10) pair plasmas to study the energization physics of high-energy particles. We identify an acceleration mechanism that only operates in 3D. For weak guide fields, 3D plasmoids/flux ropes extend along the z-direction of the electric current for a length comparable to their cross-sectional radius. Unlike in 2D simulations, where particles are buried in plasmoids, in 3D we find that a fraction of particles with γ ≳ 3σ can escape from plasmoids by moving along z, and so they can experience the large-scale fields in the upstream region. These “free” particles preferentially move in z along Speiser-like orbits sampling both sides of the layer and are accelerated linearly in time—their Lorentz factor scales as γ ∝ t, in contrast to γ ∝ t in 2D. The energy gain rate approaches ∼eE rec c, where E rec ≃ 0.1B 0 is the reconnection electric field and B 0 the upstream magnetic field. The spectrum of free particles is hard, dN free / d γ ∝ γ − 1.5 , contains ∼20% of the dissipated magnetic energy independently of domain size, and extends up to a cutoff energy scaling linearly with box size. Our results demonstrate that relativistic reconnection in GRB and AGN jets may be a promising mechanism for generating ultra-high-energy cosmic rays.
11
Yang, Hengye, Gregory P. Bewley, and Silvia Ferrari. "A Fast-Tracking-Particle-Inspired Flow-Aided Control Approach for Air Vehicles in Turbulent Flow." Biomimetics 7, no. 4 (November 6, 2022): 192. http://dx.doi.org/10.3390/biomimetics7040192.
Анотація:
Natural phenomena such as insect migration and the thermal soaring of birds in turbulent environments demonstrate animals’ abilities to exploit complex flow structures without knowledge of global velocity profiles. Similar energy-harvesting features can be observed in other natural phenomena such as particle transport in turbulent fluids. This paper presents a new feedback control approach inspired by experimental studies on particle transport that have recently illuminated particles’ ability to traverse homogeneous turbulence through the so-called fast-tracking effect. While in nature fast tracking is observed only in particles with inertial characteristics that match the flow parameters, the new fast-tracking feedback control approach presented in this paper employs available propulsion and actuation to allow the vehicle to respond to the surrounding flow in the same manner as ideal fast-tracking particles would. The resulting fast-tracking closed-loop controlled vehicle is then able to leverage homogeneous turbulent flow structures, such as sweeping eddies, to reduce travel time and energy consumption. The fast-tracking approach is shown to significantly outperform existing optimal control solutions, such as linear quadratic regulator and bang-bang control, and to be robust to changes in the vehicle characteristics and/or turbulent flow parameters.
12
Lazarian, A., G. Kowal, E. de Gouveia Dal Pino, and E. Vishniac. "Particle acceleration in fast magnetic reconnection." Proceedings of the International Astronomical Union 6, S274 (September 2010): 62–71. http://dx.doi.org/10.1017/s1743921311006582.
Анотація:
AbstractOur numerical simulations show that the reconnection of magnetic field becomes fast in the presence of weak turbulence in the way consistent with the Lazarian & Vishniac (1999) model of fast reconnection. This process in not only important for understanding of the origin and evolution of the large-scale magnetic field, but is seen as a possibly efficient particle accelerator producing cosmic rays through the first order Fermi process. In this work we study the properties of particle acceleration in the reconnection zones in our numerical simulations and show that the particles can be efficiently accelerated via the first order Fermi acceleration.
13
Stansby, D., D. Perrone, L. Matteini, T. S. Horbury, and C. S. Salem. "Alpha particle thermodynamics in the inner heliosphere fast solar wind." Astronomy & Astrophysics 623 (February 28, 2019): L2. http://dx.doi.org/10.1051/0004-6361/201834900.
Анотація:
Context. Plasma processes occurring in the corona and solar wind can be probed by studying the thermodynamic properties of different ion species. However, most in situ observations of positive ions in the solar wind are taken at 1 AU, where information on their solar source properties may have been irreversibly erased. Aims. In this study we aim to use the properties of alpha particles at heliocentric distances between 0.3 AU and 1 AU to study plasma processes occurring at the points of observation, and to infer processes occurring inside 0.3 AU by comparing our results to previous remote sensing observations of the plasma closer to the Sun. Methods. We reprocessed the original Helios positive ion distribution functions, isolated the alpha particle population, and computed the alpha particle number density, velocity, and magnetic field perpendicular and parallel temperatures. We then investigated the radial variation of alpha particle temperatures in fast solar wind observed between 0.3 AU and 1 AU. Results. Between 0.3 AU and 1 AU alpha particles are heated in the magnetic field perpendicular direction and cooled in the magnetic field parallel direction. Alpha particle evolution is bounded by the alpha firehose instability threshold, which provides one possible mechanism to explain the observed parallel cooling and perpendicular heating. Closer to the Sun our observations suggest that the alpha particles undergo heating in the perpendicular direction, whilst the large magnetic field parallel temperatures observed at 0.3 AU may be due to the combined effect of double adiabatic expansion and alpha particle deceleration inside 0.3 AU.
14
Fu, Lin, Zhe Ji, Xiangyu Y. Hu, and Nikolaus A. Adams. "Parallel fast-neighbor-searching and communication strategy for particle-based methods." Engineering Computations 36, no. 3 (April 8, 2019): 899–929. http://dx.doi.org/10.1108/ec-05-2018-0226.
Анотація:
Purpose This paper aims to develop a parallel fast neighbor search method and communication strategy for particle-based methods with adaptive smoothing-length on distributed-memory computing systems. Design/methodology/approach With a multi-resolution-based hierarchical data structure, the parallel neighbor search method is developed to detect and construct ghost buffer particles, i.e. neighboring particles on remote processor nodes. To migrate ghost buffer particles among processor nodes, an undirected graph is established to characterize the sparse data communication relation and is dynamically recomposed. By the introduction of an edge coloring algorithm from graph theory, the complex sparse data exchange can be accomplished within optimized frequency. For each communication substep, only efficient nonblocking point-to-point communication is involved. Findings Two demonstration scenarios are considered: fluid dynamics based on smoothed-particle hydrodynamics with adaptive smoothing-length and a recently proposed physics-motivated partitioning method [Fu et al., JCP 341 (2017): 447-473]. Several new concepts are introduced to recast the partitioning method into a parallel version. A set of numerical experiments is conducted to demonstrate the performance and potential of the proposed parallel algorithms. Originality/value The proposed methods are simple to implement in large-scale parallel environment and can handle particle simulations with arbitrarily varying smoothing-lengths. The implemented smoothed-particle hydrodynamics solver has good parallel performance, suggesting the potential for other scientific applications.
15
Wu, Guorong, Zhanfei Zuo, and Yanggui Li. "Selection of Relative DEM Time Step for Modelling Fast Fluidized Bed of A-Type FCC Particles." Symmetry 15, no. 2 (February 13, 2023): 488. http://dx.doi.org/10.3390/sym15020488.
Анотація:
In chemical production processes, the most suitable operation regime for A-Type powders such as typical FCC particles is high-speed fast fluidization owing to their uniquely advantageous properties. Discrete element method (DEM) for modelling fast fluidization with A-Type powders has rarely been reported. How to appropriately select the DEM time step and the stiffness coefficient is one of the most critical problems for stable and accurate calculation. This article mainly discusses the effect of the stiffness coefficient and DEM time step on simulations of A-type FCC particles. In order to describe the effect of both parameters and their complex interaction, a dimensionless relative DEM time step is introduced. In total, nine cases with different numbers of relative time steps are adopted for modelling a microfluidized bed of A-Type FCC particles, the regime of which is proved to be fast fluidization. Results show that three bifurcations occur in all the simulations. Only the moderate relative time step possesses the capability of modelling the process of particle collision and thus predicts the right flow regime with asymmetric and heterogeneous typical fast fluidized structures. When the relative time step increases to large rank, simulations predict untrue fluidization regimes with symmetric and homogeneous structures. Moreover, both over-large and over-low relative time steps cause excessive particle overlap and thus a divergence of simulation. The further optimization of moderate relative DEM time step in relation to real particle property is unidentifiable and is thus an outstanding issue. That the range of the moderate relative time step is limited indicates that the common soft-sphere model is poor at modelling fast fluidization of A-Type particles. It is suggested that possible future work should be focused on improving the simulation frame and employing the molecular dynamics model to more appropriately deal with particle contact.
16
Buncher, Brandon, and Matias Carrasco Kind. "Probabilistic cosmic web classification using fast-generated training data." Monthly Notices of the Royal Astronomical Society 497, no. 4 (July 13, 2020): 5041–60. http://dx.doi.org/10.1093/mnras/staa2008.
Анотація:
ABSTRACT We present a novel method of robust probabilistic cosmic web particle classification in three dimensions using a supervised machine learning algorithm. Training data were generated using a simplified ΛCDM toy model with pre-determined algorithms for generating haloes, filaments, and voids. While this framework is not constrained by physical modelling, it can be generated substantially more quickly than an N-body simulation without loss in classification accuracy. For each particle in this data set, measurements were taken of the local density field magnitude and directionality. These measurements were used to train a random forest algorithm, which was used to assign class probabilities to each particle in a ΛCDM, dark matter-only N-body simulation with 2563 particles, as well as on another toy model data set. By comparing the trends in the ROC curves and other statistical metrics of the classes assigned to particles in each data set using different feature sets, we demonstrate that the combination of measurements of the local density field magnitude and directionality enables accurate and consistent classification of halo, filament, and void particles in varied environments. We also show that this combination of training features ensures that the construction of our toy model does not affect classification. The use of a fully supervised algorithm allows greater control over the information deemed important for classification, preventing issues arising from arbitrary hyperparameters and mode collapse in deep learning models. Due to the speed of training data generation, our method is highly scalable, making it particularly suited for classifying large data sets, including observed data.
17
Yin, Zhao Qin, Jian Zhong Lin, and Li Juan Qian. "An Experimental Study on the Characteristics of Nanoparticles Emission from a Vehicle." Advanced Materials Research 508 (April 2012): 180–83. http://dx.doi.org/10.4028/www.scientific.net/amr.508.180.
Анотація:
The Fast Mobility Particle Sizer (FMPS) has been used to measure the particles number concentration and size distribution (6-560nm) of vehicle exhaust plume. The results reveal that vehicle exhaust contribute dominantly to the number concentration in the atmosphere particle. The particles total concentration decreases in the dispersion process. Furthermore, the transformation processes such as nucleation ,coagulation and condensation happen with dispersion process. Because of large number of nucleation mode particles, the coagulation process is in the advantage, which make the particles diameter increase.
18
Zhang, Wanxin, Bingrui Huang, Sijie Meng, and Jihong Zhu. "Infrared Fast-Maneuvering Target Tracking Based on Robust Exact Differentiator with Improved Particle Filter." Journal of Robotics 2022 (October 21, 2022): 1–9. http://dx.doi.org/10.1155/2022/6406672.
Анотація:
This paper deals with the problem of nonlinear uncertainties when tracking an infrared dim small target with fast maneuvers. The particle filter (PF)-based methods are mostly considered. The existing improvement methods for the PF can handle the infrared dim small target with the conventional maneuver, the motion state of which changes slowly and in most cases is assumed to be linear. However, when fast maneuvers appear on the target, the PF-based method will soon suffer from particle degeneracy, or even loss of the target. In this paper, a robust exact differentiator (RED)-based particle generating method is proposed to improve the PF. New birth particles are produced by the proposed method, which can keep up with the fast maneuvers, and ensure the particle diversity of the PF, so as to avoid the particle degeneracy and depletion, meanwhile the number of particles required can be decreased. Numerical simulations are conducted, showing that the proposed algorithm has more advantages than the state-of-the-art method.
19
Zhevago, N. K., and V. I. Glebov. "Channeling of fast particles in fullerites." Journal of Experimental and Theoretical Physics 94, no. 6 (June 2002): 1121–33. http://dx.doi.org/10.1134/1.1493164.
20
Badziak, J. "Laser-driven generation of fast particles." Opto-Electronics Review 15, no. 1 (January 1, 2007): 1–12. http://dx.doi.org/10.2478/s11772-006-0048-3.
Анотація:
AbstractThe great progress in high-peak-power laser technology has resulted recently in the production of ps and subps laser pulses of PW powers and relativistic intensities (up to 1021 W/cm2) and has laid the basis for the construction of multi-PW lasers generating ultrarelativistic laser intensities (above 1023 W/cm2). The laser pulses of such extreme parameters make it possible to produce highly collimated beams of electrons or ions of MeV to GeV energies, of short time durations (down to subps) and of enormous currents and current densities, unattainable with conventional accelerators. Such particle beams have a potential to be applied in numerous fields of scientific research as well as in medicine and technology development. This paper is focused on laser-driven generation of fast ion beams and reviews recent progress in this field. The basic concepts and achievements in the generation of intense beams of protons, light ions, and multiply charged heavy ions are presented. Prospects for applications of laser-driven ion beams are briefly discussed.
21
Arias, Rodrigo, and H. Neal Bertram. "Fast thermal reversal of magnetic particles." Journal of Magnetism and Magnetic Materials 171, no. 1-2 (July 1997): 209–17. http://dx.doi.org/10.1016/s0304-8853(97)00053-x.
22
Suess, D., T. Schrefl, W. Scholz, and J. Fidler. "Fast switching of small magnetic particles." Journal of Magnetism and Magnetic Materials 242-245 (April 2002): 426–29. http://dx.doi.org/10.1016/s0304-8853(01)01140-4.
23
Wurz, Peter, and Lukas Gubler. "Fast microchannel plate detector for particles." Review of Scientific Instruments 67, no. 5 (May 1996): 1790–93. http://dx.doi.org/10.1063/1.1146975.
24
Kim, Kyou Hyun, Hoon Park, Jae Pyong Ahn, Jael Chul Lee, and Jong Ku Park. "HRTEM Study of Phase Transformation from Anatase to Rutile in Nanocrystalline TiO2 Particles." Materials Science Forum 534-536 (January 2007): 65–68. http://dx.doi.org/10.4028/www.scientific.net/msf.534-536.65.
Анотація:
The spherical anatase TiO2 nanoparticle of 50 nm in diameter was manufactured by flame method and was subsequently heat-treated to investigate the transformation behavior from anatase to rutile using TEM observation. The anatase particle was facetted at the free surface and a neck formed between the anatase particles prior to the phase transformation. This resulted in the severe lattice distortion at the region of the interface. Unfortunately, we could not find the rutile grain nucleated in the anatase particle due to very fast grain growth. All the phase boundaries observed in HRTEM images existed in the contact between anatase and rutile particles. The nucleation of rutile phase in anatase particle was suppressed at the low heat-treated temperature but the grain growth of rutile particles after the phase transformation grew very fast by the sweeping phenomena of grain boundary. It leaded to the microstructure without the rutile phase traped in anatase particle.
25
Luo, Mei, Guanyi Wang, Aleksandar S. Mijailovic, Jian Yang, Brain W. Sheldon, Qingliu Wu, and Wenquan Lu. "How Graphite Particle Sizes Affect Fast Charging Performance of Ultra-Thin Layer Electrodes for Li- Ion Batteries." ECS Meeting Abstracts MA2023-01, no. 2 (August 28, 2023): 504. http://dx.doi.org/10.1149/ma2023-012504mtgabs.
Анотація:
Extreme fast charging (XFC, ≤15 min) of lithium-ion batteries is highly desirable to accelerate mass market adoption of electric vehicles.[1] However, great capacity fading, as well as safety issues due to the lithium plating, limit its implementation. In this study, we investigated the fast-charging capability of graphite materials with various particle sizes under different charging currents up to 6C. To eliminate Li+ ion gradients effects across the thickness of electrode[2], ultra-thin layer graphite electrodes were developed to investigate the “real" fast-charging capability of graphite at particle level by assessing its lithium plating limit. Observations derived from the electrochemical results as well as microscopy characterization revealed that smaller particles exhibited a superior fast-charging performance including better capacity reversibility, less polarization and less lithium plating. Moreover, smaller particles are observed to be able to handle higher C rate charging without Li plating, graphite electrodes with particle size of ~5μm can be safely charged to 80% SOC at 4C. While with particle size of ~15 μm, Li plating occurred on the graphite electrode at 2C. According to pseudo-2-dimensional (P2D) model, the superiority of the small particles might be due to the faster diffusion and intercalation through the particle because of their smaller size and faster rate kinetics due to their larger surface area. This work can help us to better understand the fast-charging behavior and provide the guidance to design the optimum electrode architecture for high-rate of lithium-ion batteries. Keywords: Ultra-thin electrode, Graphite Electrode, Particle Size, Fast Charging, Li-Ion Batteries [1] D. Howell et al., “Enabling Fast Charging: A Technology Gap Assessment,” 2017. [2] K. P. C. Yao, J. S. Okasinski, K. Kalaga, I. A. Shkrob, and D. P. Abraham, “Quantifying lithium concentration gradients in the graphite electrode of Li-ion cells using operando energy dispersive X-ray diffraction,” Energy Environ Sci, vol. 12, no. 2, pp. 656–665, Feb. 2019, doi: 10.1039/C8EE02373E.
26
Trofymenko, Sergii, Igor Kyryllin, and Oleksandr Shchus. "On the Impact Parameter Dependence of the Ionization Energy Loss of Fast Negatively Charged Particles in an Oriented Crystal." 4, no. 4 (December 10, 2021): 68–75. http://dx.doi.org/10.26565/2312-4334-2021-4-07.
Анотація:
When a fast charged particle passes through matter, it loses some of its energy to the excitation and ionization of atoms. This energy loss is called ionization energy loss. In rather thin layers of matter, the value of such energy loss is stochastic. It is distributed in accordance with the law, which was first received by L.D. Landau. In amorphous substances, such a distribution (or spectrum), known as the Landau distribution, has a single maximum that corresponds to the most probable value of particle energy loss. When a particle moves in crystal in a planar channeling mode, the probability of close collisions of the particle with atoms decreases (for a positive particle charge) or increases (for a negative charge), which leads to a change in the most probable energy loss compared to an amorphous target. It has recently been shown that during planar channeling of negatively charged particles in a crystal, the distribution of ionization energy loss of the particles is much wider than in the amorphous target. In this case, this distribution can be two-humped, if we neglect the incoherent scattering of charged particles on the thermal oscillations of the crystal atoms and the electronic subsystem of the crystal. This paper explains the reason for this distribution of ionization energy loss of particles. The ionization energy loss distribution of high-energy negatively charged particles which move in the planar channeling mode in a silicon crystal are studied with the use of numerical simulation. The dependence of this distribution on the impact parameter of the particles with respect to atomic planes is considered. The dependence of the most probable ionization energy loss of particles on the impact parameter is found. It is shown that, for a large group of particles, the most probable ionization energy loss during planar channeling in a crystal is lower than in an amorphous target.
27
Zhang, Jiaoshi, Steven Spielman, Yang Wang, Guangjie Zheng, Xianda Gong, Susanne Hering, and Jian Wang. "Rapid measurement of RH-dependent aerosol hygroscopic growth using a humidity-controlled fast integrated mobility spectrometer (HFIMS)." Atmospheric Measurement Techniques 14, no. 8 (August 18, 2021): 5625–35. http://dx.doi.org/10.5194/amt-14-5625-2021.
Анотація:
Abstract. The ability of aerosol particles to uptake water (hygroscopic growth) is an important determinant of aerosol optical properties and radiative effects. Aerosol hygroscopic growth is traditionally measured by humidified tandem differential mobility analyzers (HTDMA), in which size-selected dry particles are exposed to elevated relative humidity (RH), and the size distribution of humidified particles is subsequently measured using a scanning mobility particle sizer. As a scanning mobility particle sizer can measure only one particle size at a time, HTDMA measurements are time consuming, and ambient measurements are often limited to a single RH level. Pinterich et al. (2017b) showed that fast measurements of aerosol hygroscopic growth are possible using a humidity-controlled fast integrated mobility spectrometer (HFIMS). In HFIMS, the size distribution of humidified particles is rapidly captured by a water-based fast integrated mobility spectrometer (WFIMS), leading to a factor of ∼10 increase in measurement time resolution. In this study we present a prototype HFIMS that extends fast hygroscopic growth measurements to a wide range of atmospherically relevant RH values, allowing for more comprehensive characterizations of aerosol hygroscopic growth. A dual-channel humidifier consisting of two humidity conditioners in parallel is employed such that aerosol RH can be quickly stepped among different RH levels by sampling from alternating conditioners. The measurement sequence is also optimized to minimize the transition time between different particle sizes. The HFIMS is capable of measuring aerosol hygroscopic growth of six particle diameters under five RH levels ranging from 20 % to 85 % (30 separate measurements) every 25 min. The performance of this HFIMS is characterized and validated using laboratory-generated ammonium sulfate aerosol standards. Measurements of ambient aerosols are shown to demonstrate the capability of HFIMS to capture the rapid evolution of aerosol hygroscopic growth and its dependence on both size and RH.
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IWAI, T., C. W. HONG, and P. GREIL. "FAST PARTICLE PAIR DETECTION ALGORITHMS FOR PARTICLE SIMULATIONS." International Journal of Modern Physics C 10, no. 05 (July 1999): 823–37. http://dx.doi.org/10.1142/s0129183199000644.
Анотація:
New algorithms with O(N) complexity have been developed for fast particle-pair detections in particle simulations like the discrete element method (DEM) and molecular dynamic (MD). They exhibit robustness against broad particle size distributions when compared with conventional boxing methods. Almost similar calculation speeds are achieved at particle size distributions from is mono-size to 1:10 while the linked-cell method results in calculations more than 20 times. The basic algorithm, level-boxing, uses the variable search range according to each particle. The advanced method, multi-level boxing, employs multiple cell layers to reduce the particle size discrepancy. Another method, indexed-level boxing, reduces the size of cell arrays by introducing the hash procedure to access the cell array, and is effective for sparse particle systems with a large number of particles.
29
Scham, Moritz A. W., Dirk Krücker, Benno Käch, and Kerstin Borras. "DeepTreeGAN: Fast Generation of High Dimensional Point Clouds." EPJ Web of Conferences 295 (2024): 09010. http://dx.doi.org/10.1051/epjconf/202429509010.
Анотація:
In High Energy Physics, detailed and time-consuming simulations are used for particle interactions with detectors. To bypass these simulations with a generative model, the generation of large point clouds in a short time is required, while the complex dependencies between the particles must be correctly modelled. Particle showers are inherently tree-based processes, as each particle is produced by the decay or detector interaction of a particle of the previous generation. In this work, we present a novel Graph Neural Network model (DeepTreeGAN) that is able to generate such point clouds in a tree-based manner. We show that this model can reproduce complex distributions, and we evaluate its performance on the public JetNet dataset.
30
Tian, Xiao Feng, and Wei Ke Zhang. "Facile Synthesis of Flake Copper Powder Loaded With Silver Particles." Applied Mechanics and Materials 109 (October 2011): 91–95. http://dx.doi.org/10.4028/www.scientific.net/amm.109.91.
Анотація:
A fast and facile wet chemistry method has been developed for preparing monodispersed silver coated copper composite particles. Copper powder is coated using a solution containing [Ag (NH3)] +. The effect of the copper particle size distribution, the concentrations of [Ag (NH3)] + on composite particles conductivity were investigated. The composite particle with electric conductivity of 0.8×10-3 Ω•cm is obtained at 0.8 mol/L of Ag+ and1.0 g/L of dispersing agent. Copper powder loaded with silver particles morphologies range from individual particles to small islands, to the continuous multi-layers structure with Ag+ concentration increases.
31
Qi, Bin, Jin Tian, Jinjin Wang, and Guolong Liang. "Fast Track Smoothing Algorithm for Underwater Target Tracking Based on KD Tree." Journal of Physics: Conference Series 2486, no. 1 (May 1, 2023): 012086. http://dx.doi.org/10.1088/1742-6596/2486/1/012086.
Анотація:
Abstract A fast-track smoothing algorithm based on the KD Tree is proposed to address the problem of state estimation in underwater multi-target tracking. For multi-target tracking, the multi-Bernoulli filter becomes intractable due to the high-dimensional nature of the posterior. This problem can be overcome by the particle filter (PF), which approximates the posterior by a set of weighted samples (“particles”). The probability distribution of the multi-Bernoulli algorithm based on this algorithm contains a series of particles with weights. Therefore, while smoothing it, the state transfer probability of each particle must be computed, and the state transfer function must be calculated, which is related to the difference in states between the k-1 moment and the k moment, we refer to this difference as the state distance. However, the KD Tree can be used to divide the particle set into different state spaces according to the particle states, and thus calculate the state distances more efficiently. The remarkable feature of this algorithm is that the time complexity is greatly reduced from that O(N2) of the traditional algorithm to O(NlogN). This paper implements the proposed method using particles, the improved algorithm based on KD tree effectively mitigates the disadvantages of previous forward-backward smoothing algorithms, and significantly reduces the computation time while improving the system state estimation precision. Experimental results of simulation analysis and the optimal sub-patten assignment distance is employed as an assessment criterion to validate the algorithm’s performance.
32
John, J., P. Wollmer, M. Dahlback, A. Luts, and B. Jonson. "Tidal volume and alveolar clearance of insoluble particles." Journal of Applied Physiology 76, no. 2 (February 1, 1994): 584–88. http://dx.doi.org/10.1152/jappl.1994.76.2.584.
Анотація:
We studied the effect of 3 h of large tidal volume ventilation on alveolar clearance of 0.63-micron fluorescent latex particles in rabbits during pentobarbital anesthesia. After particle deposition, six animals were killed as controls, six were subjected to large tidal volume ventilation with a peak pressure of 27 cmH2O, and six were subjected to conventional ventilation with a peak pressure of 11 cmH2O. Mean tidal volumes were 30.2 +/- 6.1 and 8.4 +/- 1.6 ml/kg in the large tidal volume and conventional groups, respectively. End-expiratory pressure was 2 cmH2O in all groups. Compliance decreased only after large tidal ventilation (P = 0.0036). Compared with controls the conventional ventilation group showed no alveolar clearance, but more particles were clustered within macrophages (P = 0.01). Compared with other groups the large tidal volume group had fewer alveolar particles (P = 0.0005), most of which were single particles. Accordingly, large tidal volumes enhance alveolar particle clearance, which is possibly related to distension-related evacuation of surfactant to proximal airways. Clearance may be due to accelerated motion of the particle-loaded macrophage in response to the fast film motion. Alternatively, single particles embedded in the surfactant film may be dragged by the fast-moving film toward the airways.
33
Li, XiaoMing, ZiYi Wang, Yi Ying, and FangXiong Xiao. "Multipopulation Particle Swarm Optimization Algorithm with Neighborhood Learning." Scientific Programming 2022 (January 25, 2022): 1–20. http://dx.doi.org/10.1155/2022/8312450.
Анотація:
Particle swarm optimization (PSO) algorithm is widely used due to its fewer control parameters and fast convergence speed. However, as its learning strategy is only learning from the global optimal particle, the algorithm has the problem of low accuracy and easily falling into local optimization. In order to overcome this defect, a multipopulation particle swarm optimization algorithm with neighborhood learning (MPNLPSO) is proposed in this article. In MPNLPSO, a small-world network neighborhood learning strategy is proposed to make particles learn from the neighborhood optimal particles instead of only the global optimal particle. Furthermore, the concept of multipopulation cooperation is introduced to balance the ability of global exploration and local exploration. In addition, a dynamic opposition-based learning strategy is proposed to effectively activate the particles in the search stagnation state. Moreover, in order to improve the accuracy of the algorithm and, to some extent, avoid the population diversity decreases too fast, as the searching process continues, Lévy flight is introduced to randomly perturb the particles of historical optimal and neighborhood optimal. To verify the performance of the proposed algorithm experimentally, twenty benchmark functions are solved. Experimental results show that the proposed multipopulation particle swarm optimization algorithm with neighborhood learning presents high efficiency and performance with a certain robustness.
34
Sánchez, Mario A., Juan C. Maya, Farid Chejne, Brennan Pecha, and Adriana M. Quinchía-Figueroa. "Mathematical Modeling of Multi-Phenomena Anisotropic Systems: Ejection of Primary Aerosols during the Fast Pyrolysis of Biomass." Mathematics 12, no. 6 (March 21, 2024): 925. http://dx.doi.org/10.3390/math12060925.
Анотація:
This study introduces a novel particle model for biomass fast pyrolysis, incorporating an anisotropic cylindrical particle to address mass and energy transport coupled with aerosol ejection, which previous models have overlooked. The main contribution lies in developing a model that considers aerosol generation in anisotropic cylindrical particles for the first time, addressing bubbling dynamics and bursting within the liquid phase. The population balance equation describes bubble dynamics and aerosol formation, capturing phenomena like nucleation, growth, coalescence, and bursting. The model employs the method of moments with bubble volume as an internal variable, substantially reducing computational costs by eliminating dependence on this variable. Results highlight the significant impact of anisotropy and particle size on aerosol ejection: smaller, less elongated particles experience faster heating, quicker conversion, and the increased accumulation of the liquid intermediate phase. Specifically, 1 mm diameter particles yield higher concentrations of metaplast and bio-oil aerosols, exceeding 15%, compared to concentrations below 11% for 3 mm particles. This model provides insights into aerosol structure (volume, surface area), aiding in understanding aerosol reactivity at the reactor scale.
35
Hofer, M. Y., R. G. Marsden, T. R. Sanderson, and C. Tranquille. "From the Sun’s south to the north pole – Ulysses COSPIN/LET composition measurements at solar maximum." Annales Geophysicae 21, no. 6 (June 30, 2003): 1383–91. http://dx.doi.org/10.5194/angeo-21-1383-2003.
Анотація:
Abstract. Based on elemental abundance ratios derived from the Ulysses COSPIN/LET measurements, we classified the energetic particle populations during and after the socalled Fast Latitude Scan – the time period during which the Ulysses spacecraft traveled from the highest heliolatitude south to maximum northern latitude, i.e. 27 November 2000 to 13 October 2001 – as being mixed between solar energetic particles (major component) and particles accelerated at stream interaction regions. During the fast latitude scan, the Ulysses spacecraft made the first transit in heliolatitude from pole to pole during solar activity maximum conditions, providing a unique opportunity to acquire energetic particle composition data over a maximum range of heliolatitudes in the inner heliosphere. At low latitudes, based on our elemental abundance analysis, we found that while solar energetic particles dominated, there were indications for particle acceleration at single compression regions in a few instances. In the high heliolatitude range the observed elemental particle compositions are mainly of the solar energetic particle type. Within the statistical errors, the observed abundance ratios were independent of latitude, and were characteristic of solar energetic particles. These observations raise an important question for the theories of particle propagation in the inner heliosphere. The daily elemental abundance ratios of S/O, Mg/O and Si/O shown here are the first measured ratios at high heliolatitudes in the energy range from 13.0 to 30.0 MeV/n.Key words. Interplanetary physics (energetic particles; interplanetary shocks) – Solar physics, astrophysics and astronomy (flares and mass ejections)
36
Wu, Guorong, Qiang Li, and Zhanfei Zuo. "CFD-DEM Simulation of Fast Fluidization of Fine Particles in a Micro Riser." Processes 11, no. 8 (August 11, 2023): 2417. http://dx.doi.org/10.3390/pr11082417.
Анотація:
In recent years, the discrete element method (DEM) has gradually been applied to the traditional fluidization simulation of fine particles in a micro fluidized bed (MFB). The application of DEM in the simulating fast fluidization of fine particles in MFB has not yet received attention. This article presents a drag model that relies on the surrounding environment of particles, namely the particle circumstance-dependent drag model or PCDD model. Fast fluidization in an MFB of fine particles is simulated using DEM based on the PCDD model. Simulations indicate that the local structure in an MFB exhibits particle aggregation, which is a natural property of fast fluidization, forming a structure where a continuous dilute phase and dispersed concentrated phase coexist. There exists a strong effect of solid back-mixing in an MFB, leading to relatively low outlet solid flux. The gas back-mixing effect is, however, not so distinct. The axial porosity shows a monotonically increasing distribution with the bed height but does not strictly follow the single exponential distribution. The solid volume fraction at the bottom of the bed is significantly lower than the correlated value in CFB. The axial heterogeneous distribution of the cross-sectional average porosity in the lower half of the bed is also weakened. The radial porosity shows a higher distribution pattern in the central region and a lower one in the sidewall region.
37
Mileva, Daniela, Jingbo Wang, Markus Gahleitner, Katalee Jariyavidyanont, and René Androsch. "New Insights into Crystallization of Heterophasic Isotactic Polypropylene by Fast Scanning Chip Calorimetry." Polymers 12, no. 8 (July 28, 2020): 1683. http://dx.doi.org/10.3390/polym12081683.
Анотація:
The crystallization kinetics of metallocene-catalyzed heterophasic isotactic polypropylene composed of a matrix of isotactic polypropylene (iPP) and rubbery particles made of random ethylene–propylene copolymers (EPC), often denoted as heterophasic iPP copolymers, was analyzed as a function of the cooling rate and supercooling in nonisothermal and isothermal crystallization experiments, respectively. Fast scanning chip calorimetry (FSC) allowed assessing crystallization at processing-relevant conditions, and variation of the content (0–39 wt %) and composition (0–35 wt % propylene counits) of the EPC particles revealed qualitatively new insight about mechanisms of heterogeneous crystal nucleation. For neat iPP homopolymer, the characteristic bimodal temperature dependence of the crystallization rate due to predominance of heterogeneous and homogeneous crystal nucleation at high and low temperatures, respectively, is reconfirmed. At high temperatures, in heterophasic iPP, the here studied ethylene-(C2)-rich EPC particles accelerate crystallization of the iPP-matrix, with the acceleration or nucleation efficacy correlating with the EPC-particle content. The crystallization time reduces by more than half in presence of 39 wt % EPC particles. An additional nucleating effect of the EPC particles on iPP-matrix crystallization is detected after their crystallization, suggesting that liquid/rubbery particles are less effective than solid/semicrystalline particles in affecting crystallization of the surrounding iPP-matrix. At low temperature, homogeneous crystal nucleation in the iPP-matrix outpaces all heterogeneous nucleation effects, and the matrix-crystallization rate is independent of the sample composition. The obtained results lead to the conclusion that the crystallization kinetics of iPP can be affected significantly by the content and composition of EPC particles, even towards superfast crystallizing iPP grades.
38
Rantala, Antti, Pauli Pihajoki, Matias Mannerkoski, Peter H. Johansson, and Thorsten Naab. "mstar – a fast parallelized algorithmically regularized integrator with minimum spanning tree coordinates." Monthly Notices of the Royal Astronomical Society 492, no. 3 (January 15, 2020): 4131–48. http://dx.doi.org/10.1093/mnras/staa084.
Анотація:
ABSTRACT We present the novel algorithmically regularized integration method mstar for high-accuracy (|ΔE/E| ≳ 10−14) integrations of N-body systems using minimum spanning tree coordinates. The twofold parallelization of the $\mathcal {O}(N_\mathrm{part}^2)$ force loops and the substep divisions of the extrapolation method allow for a parallel scaling up to NCPU = 0.2 × Npart. The efficient parallel scaling of mstar makes the accurate integration of much larger particle numbers possible compared to the traditional algorithmic regularization chain (ar-chain) methods, e.g. Npart = 5000 particles on 400 CPUs for 1 Gyr in a few weeks of wall-clock time. We present applications of mstar on few particle systems, studying the Kozai mechanism and N-body systems like star clusters with up to Npart = 104 particles. Combined with a tree or fast multipole-based integrator, the high performance of mstar removes a major computational bottleneck in simulations with regularized subsystems. It will enable the next-generation galactic-scale simulations with up to 109 stellar particles (e.g. $m_\star = 100 \, \mathrm{M}_\odot$ for an $M_\star = 10^{11} \, \mathrm{M}_\odot$ galaxy), including accurate collisional dynamics in the vicinity of nuclear supermassive black holes.
39
Agus, Joanne, Carlito Lebrilla, Christopher Rhodes, Xinyu Tang, Maurice Wong, Chenghao Zhu, and Angela Zivkovic. "Prolonged Fasting Alters the Size, Function, and Glycoproteomic Profile of HDL Particles." Current Developments in Nutrition 6, Supplement_1 (June 2022): 435. http://dx.doi.org/10.1093/cdn/nzac057.001.
Анотація:
Abstract Objectives To investigate the effects of a single 36-hour fast on HDL glycoproteomic composition on isolated HDL particles. Methods We obtained plasma from a previous study where 20 healthy subjects, age 20–40, fasted for 36 hours. HDL was isolated using density-based ultracentrifugation steps, followed by size-exclusion chromatography. Glycoproteomic was analyzed using a targeted LC-MS/MS method, and lipoprotein particle size distribution analysis using nuclear magnetic resonance (NMR) spectroscopy. Results HDL-associated apolipoprotein A-IV (ApoA-IV) content was significantly reduced (8918.39 +/− 3823.39 normalized ion counts vs 3690.82 +/− 2147.29 normalized ion count, p adjusted < 0.0001), suggesting a reduction in intestinally-derived HDL after a 36-hour fast. HDL associated apolipoprotein C-III (ApoC-III) di-sialylated glycopeptides decreased in HDL following a 36-hour fast compared to an overnight 12-hour fast (0.1680 +/− 0.0342 normalized ion counts vs 0.1315 +/− 0.0373 normalized ion counts, p adjusted = 0.041). Additionally, particle size distribution analysis showed an increase in abundance of calibrated large HDL of size 9.6–13nm (3.42 +/− 2.218 μmol/L vs 3.885 +/− 2.134 μmol/L, p adjusted = 0.011) and a decrease in abundance of medium HDL of size 8.1–9.5nm (6.88 +/− 1.86 μmol/L vs 5.82 +/− 2.048 μmol/L, p adjusted = 0.019) after a 36-hour fast. There were no significant changes in LDL particle size (21.115 +/− nm s 21.205 +/− 0.458 nm, p adjusted = 0.655) but there was a significant increase in overall calibrated LDL particle concentration (1138.05 +/− 357.94 μmol/L vs 1262.3 +/− 313.33 μmol/L, p adjusted = 0.011) and calibrated small LDL particle concentration (454.85 +/− 187.76 μmol/L vs 598.8 +/− 190.84 μmol/L, p adjusted = 0.025). Conclusions Our findings indicate that prolonged fasting alters lipoprotein profiles by affecting the proportions of large and small HDL and LDL particles, as well as altering the protein composition of HDL particles, specifically by reducing the abundance of ApoA-IV, which suggests a reduction in the contribution of intestinally-derived HDL particles to the circulating HDL pool. Future studies are needed to determine the long-term effects of multiple bouts of prolonged fasting. Funding Sources University of California Davis, National Institute on Aging.
40
Lebensztayn, Elcio, Fábio Prates Machado та Mauricio Zuluaga Martinez. "Nonhomogeneous random walks systems on ℤ". Journal of Applied Probability 47, № 2 (червень 2010): 562–71. http://dx.doi.org/10.1239/jap/1276784909.
Анотація:
We consider a random walks system on ℤ in which each active particle performs a nearest-neighbor random walk and activates all inactive particles it encounters. The movement of an active particle stops when it reaches a certain number of jumps without activating any particle. We prove that if the process relies on efficient particles (i.e. those particles with a small probability of jumping to the left) being placed strategically on ℤ, then it might survive, having active particles at any time with positive probability. On the other hand, we may construct a process that dies out eventually almost surely, even if it relies on efficient particles. That is, we discuss what happens if particles are initially placed very far away from each other or if their probability of jumping to the right tends to 1 but not fast enough.
41
Lebensztayn, Elcio, Fábio Prates Machado та Mauricio Zuluaga Martinez. "Nonhomogeneous random walks systems on ℤ". Journal of Applied Probability 47, № 02 (червень 2010): 562–71. http://dx.doi.org/10.1017/s0021900200006811.
Анотація:
We consider a random walks system on ℤ in which each active particle performs a nearest-neighbor random walk and activates all inactive particles it encounters. The movement of an active particle stops when it reaches a certain number of jumps without activating any particle. We prove that if the process relies on efficient particles (i.e. those particles with a small probability of jumping to the left) being placed strategically on ℤ, then it might survive, having active particles at any time with positive probability. On the other hand, we may construct a process that dies out eventually almost surely, even if it relies on efficient particles. That is, we discuss what happens if particles are initially placed very far away from each other or if their probability of jumping to the right tends to 1 but not fast enough.
42
Zhang, Hu, Zichuan Yi, Liming Liu, Feng Chi, Yunfeng Hu, Sida Huang, Yu Miao, and Li Wang. "A Fast-Response Driving Waveform Design Based on High-Frequency Voltage for Three-Color Electrophoretic Displays." Micromachines 13, no. 1 (December 30, 2021): 59. http://dx.doi.org/10.3390/mi13010059.
Анотація:
Three-color electrophoretic displays (EPDs) have the characteristics of colorful display, reflection display, low power consumption, and flexible display. However, due to the addition of red particles, response time of three-color EPDs is increased. In this paper, we proposed a new driving waveform based on high-frequency voltage optimization and electrophoresis theory, which was used to shorten the response time. The proposed driving waveform was composed of an activation stage, a new red driving stage, and a black or white driving stage. The response time of particles was effectively reduced by removing an erasing stage. In the design process, the velocity of particles in non-polar solvents was analyzed by Newton’s second law and Stokes law. Next, an optimal duration and an optimal frequency of the activation stage were obtained to reduce ghost images and improve particle activity. Then, an optimal voltage which can effectively drive red particles was tested to reduce the response time of red particles. Experimental results showed that compared with a traditional driving waveform, the proposed driving waveform had a better performance. Response times of black particles, white particles and red particles were shortened by 40%, 47.8% and 44.9%, respectively.
43
Jones, Bruce D., and John R. Williams. "Fast computation of accurate sphere-cube intersection volume." Engineering Computations 34, no. 4 (June 12, 2017): 1204–16. http://dx.doi.org/10.1108/ec-02-2016-0052.
Анотація:
Purpose Volume mapping of large spherical particles to a Cartesian grid with smaller grid elements is typically required in application of simple immersed boundary conditions in coupled engineering simulations. However, there exists no unique analytical solution to computation of the volume of intersection between spheres and cubes. The purpose of this paper is to determine a suitable solution to this problem depending on the required level of accuracy. Design/methodology/approach In this work, existing numerical techniques for computing intersection volume are reviewed and compared in terms of accuracy and performance. In addition to this, a more efficient linear relationship is proposed and included in this comparison. Findings The authors find in this work that a simple linear relationship is both acceptably accurate and more computationally efficient than the contemporary techniques. Originality/value This simple linear approach may be applied to accurately compute solutions to fluid-particle systems with very large numbers of particles.
44
Wijsen, N., A. Aran, J. Pomoell, and S. Poedts. "Modelling three-dimensional transport of solar energetic protons in a corotating interaction region generated with EUHFORIA." Astronomy & Astrophysics 622 (January 28, 2019): A28. http://dx.doi.org/10.1051/0004-6361/201833958.
Анотація:
Aims. We introduce a new solar energetic particle (SEP) transport code that aims at studying the effects of different background solar wind configurations on SEP events. In this work, we focus on the influence of varying solar wind velocities on the adiabatic energy changes of SEPs and study how a non-Parker background solar wind can trap particles temporarily at small heliocentric radial distances (≲1.5 AU) thereby influencing the cross-field diffusion of SEPs in the interplanetary space. Methods. Our particle transport code computes particle distributions in the heliosphere by solving the focused transport equation (FTE) in a stochastic manner. Particles are propagated in a solar wind generated by the newly developed data-driven heliospheric model, EUHFORIA. In this work, we solve the FTE, including all solar wind effects, cross-field diffusion, and magnetic-field gradient and curvature drifts. As initial conditions, we assume a delta injection of 4 MeV protons, spread uniformly over a selected region at the inner boundary of the model. To verify the model, we first propagate particles in nominal undisturbed fast and slow solar winds. Thereafter, we simulate and analyse the propagation of particles in a solar wind containing a corotating interaction region (CIR). We study the particle intensities and anisotropies measured by a fleet of virtual observers located at different positions in the heliosphere, as well as the global distribution of particles in interplanetary space. Results. The differential intensity-time profiles obtained in the simulations using the nominal Parker solar wind solutions illustrate the considerable adiabatic deceleration undergone by SEPs, especially when propagating in a fast solar wind. In the case of the solar wind containing a CIR, we observe that particles adiabatically accelerate when propagating in the compression waves bounding the CIR at small radial distances. In addition, for r ≳ 1.5 AU, there are particles accelerated by the reverse shock as indicated by, for example, the anisotropies and pitch-angle distributions of the particles. Moreover, a decrease in high-energy particles at the stream interface (SI) inside the CIR is observed. The compression/shock waves and the magnetic configuration near the SI may also act as a magnetic mirror, producing long-lasting high intensities at small radial distances. We also illustrate how the efficiency of the cross-field diffusion in spreading particles in the heliosphere is enhanced due to compressed magnetic fields. Finally, the inclusion of cross-field diffusion enables some particles to cross both the forward compression wave at small radial distances and the forward shock at larger radial distances. This results in the formation of an accelerated particle population centred on the forward shock, despite the lack of magnetic connection between the particle injection region and this shock wave. Particles injected in the fast solar wind stream cannot reach the forward shock since the SI acts as a diffusion barrier.
45
Zhang, Z., and A. Prosperetti. "A Method for Particle Simulation." Journal of Applied Mechanics 70, no. 1 (January 1, 2003): 64–74. http://dx.doi.org/10.1115/1.1530636.
Анотація:
This paper extends a recent approach to the direct numerical simulation of particle flows to the case in which the particles are not fixed. The basic idea is to use a local analytic representation valid near the particle to “transfer” the no-slip condition from the particle surface to the adjacent grid nodes. In this way the geometric complexity arising from the irregular relation between the particle boundary and the underlying mesh is avoided and fast solvers can be used. The results suggest that the computational effort increases only slowly with the number of particles so that the method is efficient for large-scale simulations. The focus here is on the two-dimensional case (cylindrical particles), but the same procedure, to be developed in forthcoming papers, applies to three dimensions (spherical particles).
46
Wu, Guorong, and Yanggui Li. "CFD-DEM Simulation of Slugging and Non-Slugging Fast Fluidization of Fine Particles in a Micro Riser." Processes 11, no. 10 (October 14, 2023): 2977. http://dx.doi.org/10.3390/pr11102977.
Анотація:
The discrete element method (DEM) coupled with computational dynamics (CFD) has been considered one of the most sensitive ways of studying the micro fluidized bed. This article proposes a so-called particle circumstance-dependent drag model that is dependent on a particle’s complex circumstances. Slugging and non-slugging fast fluidization in a micro fluidized bed is modeled with the use of the CFD-DEM. The results show that the formation and the fragmentation of clusters in a slugging fast fluidized state are clearly captured, and both have time synchronization. However, with the increase in gas velocity, the boundary of the dense and dilute phases turns blurry and the slugs disappear. Furthermore, there exists a relatively serious backmixing of particles in the slugging fast fluidization, while the backmixing effect weakens in the non-slugging fast fluidization. Moreover, the outlet solid flux decreases compared with those in the big fluidized beds for the slugging fast fluidized bed due to the micro size effect, while the micro size effect on the solid flux is not distinct for the non-slugging fast fluidized bed. Last but not least, the radial porosity with slugging exhibits a weakened core-annulus structure compared with the correlated radial porosity in the big fluidized beds. The radial porosity without slugging tends to approach the correlated core-annulus structure.
47
Santos, Jaime E., Mikhail Vasilevskiy, Nuno M. R. Peres, and Antti-Pekka Jauho. "Energy loss by fast-travelling charged particles traversing two-dimensional materials." EPJ Web of Conferences 233 (2020): 03005. http://dx.doi.org/10.1051/epjconf/202023303005.
Анотація:
We consider the problem of the radiation losses by fast-traveling particles traversing two-dimensional (2d) materials or thin films. After review¬ing the screening of electromagnetic fields by two dimensional conducting ma¬terials, we obtain the energy loss by a fast particle traversing such a material or film. In particular, we discuss the pattern of radiation emitted by monolayer graphene treated within a hydrodynamic approximation. These results are com¬pared with recent published results using similar approximations and, having in mind a potential application to particle detection, we briefly discuss how one can improve on the signals obtained by using other two-dimensional materials.
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Zuo, Tao, Huasong Min, Quan Tang, and Qiang Tao. "A Robot SLAM Improved by Quantum-Behaved Particles Swarm Optimization." Mathematical Problems in Engineering 2018 (2018): 1–11. http://dx.doi.org/10.1155/2018/1596080.
Анотація:
We propose a new SLAM method based on fast simultaneous localization and mapping (FastSLAM). The technique presented uses an improved quantum-behaved particles swarm optimization (QPSO) to improve the proposal distribution of particles and optimize the estimated particles. This method makes the sampled particles closer to the true pose of the robot and improves the estimation accuracy of robot poses and landmarks. In the QPSO algorithm, the Gaussian disturbance is added to increase the diversity of the particles. By using this technique the premature convergence of particles swarm is overcome. In the resample step, the threshold value is used to evaluate the particle diversity. When the particle diversity is below the threshold value, the linear optimization is used to produce new sample particles, which increases the particle diversity and eliminates the loss of diversity. Simulations and experiments show that the proposed approach improves the accuracy of SLAM. The accuracy of estimated poses and landmarks with the proposed method is better than that with the traditional SLAM method.
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Wang, H. D., C. N. Zhang, H. Zhang, Y. C. Wei, and X. L. Guan. "A Quantum Particle Swarm Optimization Algorithm Based on Aggregation Perturbation." Applied Science and Innovative Research 7, no. 4 (September 13, 2023): p21. http://dx.doi.org/10.22158/asir.v7n4p21.
Анотація:
A quantum particle swarm hybrid optimization algorithm based on aggregation disturbance is proposed for inventory cost control. This algorithm integrates the K-means algorithm on the basis of traditional particle swarm optimization, recalculates the clustering center, initializes stagnant particles, and solves the problem of particle aggregation. Introducing chaos mechanism into the algorithm, changing the position of particles, enhancing their activity, and improving the algorithm's global optimization ability. At the same time, define the aggregation disturbance factor, determine the current state of particles, optimize speed and position to accelerate escape, and solve the problem of particles falling into local optima. Experiments show that M-IKPSO algorithm has strong stability, fast Rate of convergence and high accuracy compared with other algorithms, and the improvement effect is significant.
50
Vishnyakov, V. I., S. A. Kiro, M. V. Oprya, and A. A. Ennan. "Self-organization of primary particles of welding fume." Physics of Aerodisperse Systems, no. 52 (March 15, 2015): 104–14. http://dx.doi.org/10.18524/0367-1631.2015.52.159789.
Анотація:
The long-range interaction of the condensed particles of welding fume is studied. It is demonstrated that the long-range interaction is the result of the ionization equilibrium displacement near the charged particle surface. The long-range interaction with the electrical repulsing force leads to formation of the ordered structures of condensed particles. As a result the local number density of the condensed particles is increased, and their fast coagulation is possible.