Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSimulation and Experimental Investigation of Cellular Material Breakage Using the Pulsed Electric Field Treatment
102
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We consider the simplified dielectric breakage model used for simulation of the kinetics of cellular material breakage under the pulsed electric field (PEF) treatment. The model is based on an effective media approximation, which includes equations with the same morphology parameters as in percolation theory. The probability of a whole cell breakage by the pulse with $t_{i}$ duration is estimated on the basis of electroporation theory. We account for the bridging effect resulting from the deviations of the local conductivity near the selected cell from the average effective media conductivity. The most important feature of the proposed model is the existence of the ``jamming behaviour occurring sometimes in experimental observations of the biological tissue breakage. The different transitions corresponding to the ``jamming steps are identified. The experimental results are obtained for thin apple slices treated with electric pulses at field strengths $E=0.2-2.2$ kV cm$^{-1}$, pulse durations $t_{i}=10-100$ $mu$s, pulse repetition times $t=10-100$ ms and the number of pulses $N=1-100000$. The model gives results consistent in general with the experimental observations. We discuss the correlation between the degree of cellular material destruction, field strength, time of PEF treatment and power consumption.
rate research
Read More
We present results of numerical and experimental investigation of the electric breakage of a cellular material in pulsed electric fields (PEF). The numerical model simulates the conductive properties of a cellular material by a two-dimensional array of biological cells. The application of an external field in the form of the idealised square pulse sequence with a pulse duration $t_{i}$, and a pulse repetition time $Delta t$ is assumed. The simulation model includes the known mechanisms of temporal and spatial evolution of the conductive properties of different microstructural elements in a tissue. The kinetics of breakage at different values of electric field strength $E$, $t_{i}$ and $Delta t$ was studied in experimental investigation. We propose the hypothesis for the nature of tissue properties evolution after PEF treatment and consider this phenomena as a correlated percolation, which is governed by two key processes: resealing of cells and moisture transfer processes inside the cellular structure. The breakage kinetics was shown to be very sensitive to the repetition times $Delta t$ of the PEF treatment. We observed correlated percolation patterns in a case when $Delta t$ exceeds the characteristic time of the processes of moisture transfer and random percolation patterns in other cases. The long-term mode of the pulse repetition times in PEF treatment allows us to visualize experimentally the macroscopic percolation channels in the sample.
Influence of pulsed electric field (PEF) simultaneous to pressure treatment on moisture expression from fine-cut cellular raw material has been investigated. Dependencies of specific conductivity $sigma$, liquid yield $Y$, instantaneous flow rate $v$ and qualitative juice characteristics at different modes of PEF treatment are discussed. Three main consolidation phases were observed in a case of mechanical expression. A unified approach is proposed for liquid yield data analysis allowing to reduce the data scattering caused by differences in the quality of samples. Simultaneous application of pressure and PEF treatment allows to reveal a passive form of electrical damage. Pressure provokes the damage of defected cells, enhances diffusion migration of moisture in porous cellular material and depresses the cell resealing processes. PEF application at a moment when a sample specific electrical conductivity reaches minimum and pressure achieves its constant value seemed to be the most optimal.
We propose a 2-dimensional cellular automaton model to simulate pedestrian traffic. It is a vmax=1 model with exclusion statistics and parallel dynamics. Long-range interactions between the pedestrians are mediated by a so called floor field which modifies the transition rates to neighbouring cells. This field, which can be discrete or continuous, is subject to diffusion and decay. Furthermore it can be modified by the motion of the pedestrians. Therefore the model uses an idea similar to chemotaxis, but with pedestrians following a virtual rather than a chemical trace. Our main goal is to show that the introduction of such a floor field is sufficient to model collective effects and self-organization encountered in pedestrian dynamics, e.g. lane formation in counterflow through a large corridor. As an application we also present simulations of the evacuation of a large room with reduced visibility, e.g. due to failure of lights or smoke.
We propose a statistical mechanics for a general class of stationary and metastable equilibrium states. For this purpose, the Gibbs extremal conditions are slightly modified in order to be applied to a wide class of non-equilibrium states. As usual, it is assumed that the system maximizes the entropy functional $S$, subjected to the standard conditions; i.e., constant energy and normalization of the probability distribution. However, an extra conserved constraint function $F$ is also assumed to exist, which forces the system to remain in the metastable configuration. Further, after assuming additivity for two quasi-independent subsystems, and that the new constraint commutes with density matrix $rho$, it is argued that F should be an homogeneous function of the density matrix, at least for systems in which the spectrum is sufficiently dense to be considered as continuous. The explicit form of $F$ turns to be $F(p_{i})=p_{i}^{q}$, where $p_i$ are the eigenvalues of the density matrix and $q$ is a real number to be determined. This $q$ number appears as a kind of Tsallis parameter having the interpretation of the order of homogeneity of the constraint $F$. The procedure is applied to describe the results of the plasma experiment of Huang and Driscoll. The experimentally measured density is predicted with a similar precision as it is done with the use of the extremum of the enstrophy and Tsallis procedures. However, the present results define the density at all the radial positions. In particular, the smooth tail shown by the experimental distribution turns to be predicted by the procedure. In this way, the scheme avoids the non-analyticity of the density profile at large distances arising in both of the mentioned alternative procedures.
We examine in detail the theoretical underpinnings of previous successful applications of local molecular field (LMF) theory to charged systems. LMF theory generally accounts for the averaged effects of long-ranged components of the intermolecular interactions by using an effective or restructured external field. The derivation starts from the exact Yvon-Born-Green hierarchy and shows that the approximation can be very accurate when the interactions averaged over are slowly varying at characteristic nearest-neighbor distances. Application of LMF theory to Coulomb interactions alone allows for great simplifications of the governing equations. LMF theory then reduces to a single equation for a restructured electrostatic potential that satisfies Poissons equation defined with a smoothed charge density. Because of this charge smoothing by a Gaussian of width sigma, this equation may be solved more simply than the detailed simulation geometry might suggest. Proper choice of the smoothing length sigma plays a major role in ensuring the accuracy of this approximation. We examine the results of a basic confinement of water between corrugated wall and justify the simple LMF equation used in a previous publication. We further generalize these results to confinements that include fixed charges in order to demonstrate the broader impact of charge smoothing by sigma. The slowly-varying part of the restructured electrostatic potential will be more symmetric than the local details of confinements.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
