Strength Of Driving Force Research Articles

Diffusion-facilitated transport of self-driven particles in polycrystalline structures

We study particle transport in a polycrystalline system with mesoscale regular structures, which was inspired by ionic transport in solids. We found a novel type of congestion dynamics in which the density of particles spontaneously became strongly inhomogeneous with increasing driving force field and inverse temperature, leaving strongly localized pathways that allowed for substantial particle current. Consequently, particle current was maximized at a certain driving force strength and inverse temperature, which effectively avoided overcrowding of particles via a moderate level of diffusion. Our findings not only extend the theory of collective transport of self-propelled particles but also provide a baseline for understanding the transport properties of real polycrystalline systems, including superionic materials. Published by the American Physical Society 2024

Ga+ Ion Irradiation-Induced Tuning of Artificial Pinning Sites to Control Domain Wall Motion

Domain-wall-based devices are considered one of the candidates for the next generation of storage memories and nanomagnetic logic devices due to their unique properties, such as nonvolatility, scalability, and low power consumption. Field or current-driven domain walls require a regular and controlled motion along the track in which they are stored in order to maintain the information integrity during operation. However, their dynamics can vary along the track due to film inhomogeneities, roughness of the edges, and thermal fluctuations. Consequently, the final position of the domain walls may be difficult to predict, making difficult the development of memory and logic applications. In this paper, we demonstrate how Ga+ ion irradiation can be used to locally modify the material properties of the Ta/CoFeB/MgO thin film, creating regions in which the domain wall can be trapped, namely motion barriers. The aim is to push the domain wall to overcome thin-film inhomogeneities effects, while stopping its motion at artificially defined positions corresponding to the irradiated regions. Increasing the driving force strength, the domain wall can escape, allowing the shifting between consecutive irradiated regions. In this way, the correct positioning of the domain walls after the motion is ensured. The study shows that the driving force strength, namely current density or magnetic field amplitude, needed to overcome the irradiated regions depends on the ion dose. These results show a reliable approach for domain wall manipulation, enabling a precise control of the domain wall position along a track with synchronous motion.

Mesoscopic Modeling of Capillarity-Induced Two-Phase Transport in a Microfluidic Porous Structure

Mesoscopic modeling at the pore scale offers great promise in exploring the underlying structure transport performance of flow through porous media. The present work studies the fluid flow subjected to capillarity-induced resonance in porous media characterized by different porous structure and wettability. The effects of porosity and wettability on the displacement behavior of the fluid flow through porous media are discussed. The results are presented in the form of temporal evolution of percentage saturation and displacement of the fluid front through porous media. The present study reveals that the vibration in the form of acoustic excitation could be significant in the mobilization of fluid through the porous media. The dependence of displacement of the fluid on physicochemical parameters like wettability of the surface, frequency along with the porosity is analyzed. It was observed that the mean displacement of the fluid is more in the case of invading fluid with wetting phase where the driving force strength is not so dominant.

Chaotic phase synchronization in bursting-neuron models driven by a weak periodic force

We investigate the entrainment of a neuron model exhibiting a chaotic spiking-bursting behavior in response to a weak periodic force. This model exhibits two types of oscillations with different characteristic time scales, namely, long and short time scales. Several types of phase synchronization are observed, such as 1:1 phase locking between a single spike and one period of the force and 1:l phase locking between the period of slow oscillation underlying bursts and l periods of the force. Moreover, spiking-bursting oscillations with chaotic firing patterns can be synchronized with the periodic force. Such a type of phase synchronization is detected from the position of a set of points on a unit circle, which is determined by the phase of the periodic force at each spiking time. We show that this detection method is effective for a system with multiple time scales. Owing to the existence of both the short and the long time scales, two characteristic phenomena are found around the transition point to chaotic phase synchronization. One phenomenon shows that the average time interval between successive phase slips exhibits a power-law scaling against the driving force strength and that the scaling exponent has an unsmooth dependence on the changes in the driving force strength. The other phenomenon shows that Kuramoto's order parameter before the transition exhibits stepwise behavior as a function of the driving force strength, contrary to the smooth transition in a model with a single time scale.

Stationary Solutions of Driven Fourth- and Sixth-Order Cahn–Hilliard-Type Equations

New types of stationary solutions of a one-dimensional driven sixth-order Cahn-Hilliard type equation that arises as a model for epitaxially growing nano-structures such as quantum dots, are derived by an extension of the method of matched asymptotic expansions that retains exponentially small terms. This method yields analytical expressions for far-field behavior as well as the widths of the humps of these spatially non-monotone solutions in the limit of small driving force strength which is the deposition rate in case of epitaxial growth. These solutions extend the family of the monotone kink and antikink solutions. The hump spacing is related to solutions of the Lambert $W$ function. Using phase space analysis for the corresponding fifth-order dynamical system, we use a numerical technique that enables the efficient and accurate tracking of the solution branches, where the asymptotic solutions are used as initial input. Additionally, our approach is first demonstrated for the related but simpler driven fourth-order Cahn-Hilliard equation, also known as the convective Cahn-Hilliard equation.

Electrochemical investigation on DNA–gemini complex films immobilized on gold electrode

The interaction of DNA with several new synthesized gemini surfactants R-α,ω-(C 16H 33N +(CH 3) 2Br −) 2 (R=C 6H 12, C 12H 24, CH 2CHOHC 2H 4 and CH 2C 6H 4CH 2) and the construction of DNA–gemini films formed on gold electrode surface were investigated with electrochemical techniques such as cyclic voltammetry and electrochemical impedance spectroscopy. It was found that these surfactants could be bound to DNA, driven by the electrostatic and hydrophobic interaction between DNA and surfactants, and the driving force strength was related to the structure of the spacer group of gemini surfactants. Among these gemini surfactants, C 6H 12-1,12-(C 16H 33N +(CH 3) 2Br −) 2 was bound to DNA, mainly driven by its hydrophobic interaction with DNA due to the strong hydrophobicity and flexibility of its spacer group, while others were bound to DNA, mainly driven by electrostatic interaction with DNA because of their relatively poor hydrophobicity and flexibility. Multi-layer films composed of DNA and R-α,ω-(C 16H 33N +(CH 3) 2Br −) 2 were prepared at gold electrodes, based on their interaction, and the electrochemical property of the resulted modified electrodes was mainly determined by the out-layer. It was found that the first R-α,ω-(C 16H 33N +(CH 3) 2Br −) 2 layer markedly neutralized the negative charges of DNA and the second R-α,ω-(C 16H 33N +(CH 3) 2Br −) 2 layer made the film density increase.