Analysis Of Particle Dynamics Research Articles

Computational analysis of magnetic field induced deposition of magnetic particles in lung alveolus in comparison to deposition produced with viscous drag and gravitational force

Abstract Magnetic targeting of drugs attached to magnetic nanoparticles with diameter ≈ 100 nm after their intravenous administration is an interesting method of drug delivery widely investigated both theoretically as well as experimentally. Our aim in this study is theoretical analysis of a magnetic aerosol targeting to the lung. Due to lung anatomy magnetic particles up to 5 μ m can be safely used, therefore the magnetic force would be stronger, moreover drag force exerted on the particle is according to Stokes law linearly dependent on the viscosity, would be weaker, because the viscosity of the air in the lung is approximately 200 fold smaller than viscosity of the blood. Lung therefore represents unique opportunity for magnetic drug targeting, as we have shown in this study by the analysis of magnetic particle dynamics in a rhythmically expanding and contracting distal and proximal alveolus subjected to high-gradient magnetic field generated by quadrupolar permanent Halbach magnet array.

Exact analysis of particle dynamics in combined field of finite duration laser pulse and static axial magnetic field

Dynamics of a charged particle is studied in the field of a relativistically intense linearly polarized finite duration laser pulse in the presence of a static axial magnetic field. For a finite duration laser pulse whose temporal shape is defined by Gaussian profile, exact analytical expressions are derived for the particle trajectory, momentum, and energy as function of laser phase. From the solutions, it is shown that, unlike for the monochromatic plane wave case, resonant phase locking time between the particle and laser pulse is finite. The net energy transferred to the particle does not increase monotonically but tends to saturate. It is further shown that appropriate tuning of cyclotron frequency of the particle with the characteristic frequency in the pulse spectrum can lead to the generation of accelerated particles with variable energies in MeV-TeV range.

Nanosecond Relaxation Dynamics of Hydrated Proteins: Water versus Protein Contributions

We have studied picosecond to nanosecond dynamics of hydrated protein powders using dielectric spectroscopy and molecular dynamics (MD) simulations. Our analysis of hydrogen-atom single particle dynamics from MD simulations focused on "main" (τ(main) ≈ tens of picoseconds) and "slow" (τ(slow) ≈ nanosecond) relaxation processes that were observed in dielectric spectra of similar hydrated protein samples. Traditionally, the interpretation of these processes observed in dielectric spectra has been ascribed to the relaxation behavior of hydration water tightly bounded to a protein and not to protein atoms. Detailed analysis of the MD simulations and comparison to dielectric data indicate that the observed relaxation process in the nanosecond time range of hydrated protein spectra is mainly due to protein atoms. The relaxation processes involve the entire structure of protein including atoms in the protein backbone, side chains, and turns. Both surface and buried protein atoms contribute to the slow processes; however, surface atoms demonstrate slightly faster relaxation dynamics. Analysis of the water molecule residence and dipolar relaxation correlation behavior indicates that the hydration water relaxes at much shorter time scales.

Large-scale analysis of magnetic particle dynamics taking into account contact force and magnetic interaction with the fast multipole method

This paper investigates a large-scale analysis of magnetic particles’ behavior in magnetic fields by using a novel method combining the discrete element method and the magnetic interaction calculation with the fast multipole method (FMM). Furthermore, the effective formulae for the derivative of the magnetic field in the FMM procedure, which is necessary to calculate magnetic forces among a large number of magnetic particles, are proposed. Numerical examples of large-scale magnetic-particle chain analysis that demonstrate the effectiveness of the proposed method are presented.

FE Analysis of Magnetic Particle Dynamics on Fixed Mesh With Level Set Function

Magnetic particles are used in various areas ranging from engineering to biomedical fields. The particles are controlled by an external magnetic field and the magnetized particles interact between themselves, resulting in some interesting behaviors. Various computational analyses have been recently presented. But, since most of these works are based on a point-dipole model, the accurate effects of a finite volume and mutual interactions are not calculated. In addition, full field analysis has a serious problem with remeshing for moving particles. This paper proposes a new approach, where the movement of particles is captured using a level set function on a fixed background mesh for magnetic field analysis. The magnetic forces on each particle by body force density are inserted into the driving forces in dynamic equations.

Multibody interactions of actuated magnetic particles used as fluid drivers in microchannels

The forced motion of superparamagnetic particles and their multibody interactions are studied in view of the application as integrated fluid drivers in microchannel systems. Previous studies on particle manipulation in open fluid volumes serve as our starting point for the analysis of particle dynamics and interplay effects in confined fluid volumes. An experimental setup is designed that offers a constant force field on all individual particles dispersed in a microchannel. Distinguishable multi-particle configurations are observed and analyzed on the basis of magnetic and hydrodynamic particle interaction mechanisms. The fluid driving performance and the efficiency of the particles are evaluated on system level by means of numerical simulation models.

Quasi-Isochronous Optics for Sub-Picosecond Bunch Length at Pohang Light Source

A lattice design was developed for a quasi-isochronous storage ring, which may produce a sub-picosecond bunch length at the 2.5 GeV Pohang Light Source (PLS) and the analysis of transverse and longitudinal particle dynamics in the designed ring was performed. Small momentum compaction factors in the PLS storage ring were obtained by varying the dispersion function to be negative in bending magnets. The shortest bunch length in the designed ring was estimated to be less than 1 ps, which is three-tenths that of a normal operation. The effects of the second-order momentum compaction factor on the transverse and longitudinal particle dynamics in the quasi-isochronous ring were investigated. The relationship between the momentum compaction factor and the bunch length, which can be obtained in the quasi-isochronous PLS storage ring was also investigated. Multiparticle tracking simulations were performed to investigate the longitudinal beam instability in the quasi-isochronous ring using a broadband impedance model.

Analysis of Particle Dynamics and Heat Transfer in Detonation Thermal Spraying Systems

A computational study of pulsed detonation thermal spraying is conducted using an axisymmetric two-dimensional transient gaseous detonation model. The variations of the particle velocity and temperature at impact on the target surface with the particle initial loading location are analyzed for different conditions. The geometry of the system and the loading locations of the particulate phase are key parameters in pulsed detonation thermal spraying. Since the process is extremely transient and the gas phase experiences a wide range of transient stages all on a timescale of a millisecond, the particle characteristics are strongly dependent on the instantaneous location in the gas stream. One cycle of detonation thermal spraying occurs on a time scale on the order of a millisecond due to the high gas velocities associated with detonation. Thus, a precise control of the process variable parameters is required to have a successful detonation coating process.

A SIMPLE MODEL FOR DYNAMIC HETEROGENEITIES IN A SUPERCOOLED LIQUID

The self-consistent mode-coupling theory (MCT) has been used to analyze the heterogeneous dynamical nature of a binary supercooled liquid. The non-Gaussian behavior is studied by analyzing the self part of the Van Hove correlation function, Gs(r, t). From the analysis of the single particle dynamics we identify a fraction (ϕM) of particles which are dynamically more active and find that ϕM increases as the temperature is decreased. This behavior is qualitatively similar to the computer simulation studies of the same system.

High-energy emission from presupernovae

The non-thermal emission in the magnetospheres of presupernova collapsing stars with initial dipole magnetic fields and a certain initial energy distribution of the charged particles in a magnetosphere is considered. The analysis of particle dynamics and its emission in the stellar magnetosphere under collapse show that the collapsing stars can be the powerful sources of a non-thermal radiation produced by the interaction of charged particles with the magnetic field. The radiation flux grows with decreasing stellar radius. This flux can be observed in the form of a radiation burst with duration equal to the stellar collapse time. The radiation flux depends on the distance to the stars, the particle spectrum and the magnetic field in the magnetosphere. The radiation flux is calculated for various collapsing stars with initial dipole magnetic fields and an initial power series, relativistic Maxwell and Boltzmann particle energy distribution in the magnetosphere. This radiation can be observed by means of modern astronomical instruments.

Anomalous dynamics of confined water at low hydration

The mobility of water molecules confined in a silica pore is studied by computer simulationin the low hydration regime, where most of the molecules reside close to the hydrophilicsubstrate. A layer analysis of the single particle dynamics of these molecules shows ananomalous diffusion with a sublinear behaviour over a long period. This behaviour isstrictly connected to the long time decay of the residence time distribution analogous towater in contact with proteins.

Electromagnetic radiation from collapsing stars -- I. The power-series distribution of particles in magnetospheres

This is the first paper in a series in which the dynamics and non-thermal emission of particles in the magnetospheres of collapsing stars, with initial dipole magnetic fields and a particular initial energy distribution of charged particles in the magnetosphere (power-series, relativistic Maxwell and Boltzmann distributions), are considered. When the star magnetosphere compresses during collapse, its magnetic field increases considerably. The cyclic electric field thus produced involves acceleration of charged particles, which generate radiation when moving in the magnetic field. The analysis of particle dynamics and particle emission in the stellar magnetosphere under collapse shows that collapsing stars can be powerful sources of non-thermal radiation, produced by the interaction of charged particles with the magnetic field. The effect can be observed by means of modern instruments. The radiation flux grows with decreasing stellar radius and frequency and can be observed in the form of a radiation pulse with duration equal to the stellar collapse time. This flux depends on the distance to the star, its magnetic field and the particle spectrum in the magnetosphere. In this paper the radiation fluxes are calculated for various collapsing stars with initial dipole magnetic fields and an initial power-series particle energy distribution in the magnetosphere.

Deterministic chaos analysis of particle dynamics in three-phase systems.

The instantaneous fluctuating velocities of particles acquired in three different flow regions of three-phase systems were measured by direct visualization. The local dynamics of particles were characterized by the deterministic chaos analysis of particle velocity fluctuations in terms of the correlation dimension obtained based on the time-delay embedding theorem. The results show that particles in the stable wake region exhibit highly chaotic velocity fluctuations with large correlation dimensions in spite of the apparently smooth trajectories with low fractal dimensions determined based on the box-counting method. In large particle systems the self-induced particle motion due to eddy shedding was found to be significant, resulting in an increase in correlation dimension with particle size. A sudden change in the correlation dimension was found to occur at the superficial gas velocity corresponding to the transition from the homogeneous bubbly flow to churn-turbulent flow regime.

Numerical Analysis of Particle Dynamics in a Bend of a Rectangular Duct by the Direct Simulation Monte Carlo Method.

A method of simulation of a gas-solid two-phase flow of intermediate concentrations is developed. Particle diffusion due to inter-particle collision is treated by using the Direct Simulation Monte Carlo method. Four existing schemes of the DSMC method are compared and it is concluded that the Belotserkovskiy-Yanitskiy (B-Y) scheme is suitable for treatment of inter-particle collision in solid paricle systems. Particle collision with the solid wall is simulated by a semiempirical collision model. The gas flow is calculated by solving the compressible Navier-Stokes equation using the third-order accuracy upwind QUICK scheme and Reynolds stress turbulence model. This model is applied for saltation state particulate flow in a bend of a three-dimensional rectangular duct, and the calculation results are shown.

Analysis of fine particle dynamics using a relational database system

Analysis of fine particle dynamics using a relational database system

An experimental investigation of gas flow in a scale model of a fluidized-bed combustor

An ambient temperature model was constructed to simulate the flow within the TVA 20 MW fluidized-bed combustor pilot plant. Scaling laws, verified by earlier results, allowed the hot combustor to be modeled by an ambient temperature bed of one-quarter linear scale. A fiber optic bubble probe, supplemented by visual observations, was used to make detailed studies of bubble characteristics within the bed at moderate to high superficial velocities. Bubble properties were measured within horizontal tube bubbles as well as in the gaps between neighboring tube bundles. The gas flow associated with the motion of visible bubbles was only about 20% of the excess gas superficial velocity for all cases. The measured bubble characteristics and the observed height of particle plumes in the freeboard caused by erupting bubbles were combined with a simple analysis of particle dynamics to estimate the gas throughflow velocity through erupting bubbles. The estimated throughflow velocity allowed an approximate balance to be achieved for the overall gas flow rate in the bed.