Variation Of Energy Barrier Research Articles

Programmable ferroelectric bionic vision hardware with selective attention for high-precision image classification

Selective attention is an efficient processing strategy to allocate computational resources for pivotal optical information. However, the hardware implementation of selective visual attention in conventional intelligent system is usually bulky and complex along with high computational cost. Here, programmable ferroelectric bionic vision hardware to emulate the selective attention is proposed. The tunneling effect of photogenerated carriers are controlled by dynamic variation of energy barrier, enabling the modulation of memory strength from 9.1% to 47.1% without peripheral storage unit. The molecular polarization of ferroelectric P(VDF-TrFE) layer enables a single device not only multiple nonvolatile states but also the implementation of selective attention. With these ferroelectric devices are arrayed together, UV light information can be selectively recorded and suppressed the with high current decibel level. Furthermore, the device with positive polarization exhibits high wavelength dependence in the image attention processing, and the fabricated ferroelectric sensory network exhibits high accuracy of 95.7% in the pattern classification for multi-wavelength images. This study can enrich the neuromorphic functions of bioinspired sensing devices and pave the way for profound implications of future bioinspired optoelectronics.

Activation of a hybrid twinning mechanism in a Cr-Ni-Si-V-N medium manganese austenitic steel containing precipitates

Twinning nucleation in a medium Mn austenitic steel containing precipitates is studied at low strain ~ 0.02, using transmission electron microscopy. In the near vicinity of the precipitates, unfaulting dislocation reaction is favored, while twinning is activated farther from the precipitates. Twin nucleation follows a hybrid mechanism, involving creation of stacking faults through classical dislocation dissociation, while those stacking faults subsequently overlapped following a non-classical alternated stacking fault pair mechanism to create a three-layer twin nucleus. The observed twinning behavior is interpreted from an energy barrier variation viewpoint within the matrix.

Dynamics of water confined in a graphene nanochannel: dependence of friction on graphene chirality

Numerous recent studies reveal that water transport through graphene-based nanochannels exhibits unconventional behavior. Theoretical and experimental works have reported that the dynamic behavior of the constrained water could be affected by the atomic structure, surface curvature, confinement height, pressure, and mechanical strain of the confining channel. However, few studies concern the role of graphene chirality in the dynamics of confined water. In the present study, using equilibrium molecular dynamics (EMD) simulations, we simulated the water flow through different graphene-based channels to investigate the influence of graphene chirality on the dynamic behavior of the confined water. The friction coefficient at the water/graphene interface was found to be dependent on the crystallographic orientation of the graphene wall. The results also indicated that the chirality-dependent friction behavior was affected by the confinement height of the channel. Detailed analyses on the physical origin of such a chirality effect suggested that the chirality-dependent friction was ascribed to the water–graphene interaction energy barrier variation when the water flow was driven along the armchair edge and zigzag edge. These findings are beneficial to the design of graphene-based nanofluidic devices.

Anomalous Attachment Behavior of Nanoparticles inside Narrow Channels

Core Ideas We examined interaction energy for a nanoparticle inside a cylindrical nanochannel. A non‐monotonic variation of energy barrier with ionic strength exists. The energy barrier can disappear at all ionic strengths. A critical ratio of inner channel radius to particle radius exists where transport is most favored. Attachment of nanoparticles is inhibited inside channels with small thicknesses. Understanding nanoparticle (NP) attachment inside narrow passages such as the pore throats of porous media and plant and animal tissues is critically important to assess the potential ecological and toxicological impact of NPs. This study investigated the attachment of a NP inside a cylindrical nano‐sized channel with finite wall thickness at various ionic strengths (ISs) by calculating the Derjaguin–Landau–Verwey–Overbeek (DLVO) interaction energy using a modified surface element integration technique. Results show that there is a critical value of the ratio of the inner channel diameter to NP diameter (RCN) at which the repulsive energy barrier reaches a maximum at a given IS and NP transport is most favored. A non‐monotonic variation of the energy barrier with IS was observed for RCNs smaller than the critical value. The repulsive energy barrier disappears at all ISs when the NP diameter is close to the inner channel diameter, resulting in favorable attachment at primary minima. The attached NP cannot be detached in these cases by a disturbance of system conditions because of increased primary‐minimum depths and accordingly enhanced adhesive forces. For a given RCN, decreasing the channel thickness can increase and decrease the interaction energy barrier and primary‐minimum depth for a NP inside the channel, respectively. Accordingly, NP attachment in primary minima is inhibited whereas transport is favored in channels with thin walls. These theoretical results provide plausible explanations of experimental observations that the retention of colloids in pore throats of porous media via straining is chemically favorable (i.e., no repulsive energy barrier exists) even at very low ISs and irreversible to reduction of the solution IS, and that NPs are favorably attached in narrow passages such as plant tissues and membrane pores.

Field dependence of antiferromagnetic domain switching in epitaxial Fe/CoO/MgO(001) systems

Utilizing the magneto-optic Kerr effect and Kerr microscopy measurements, we investigated the antiferromagnetic (AFM) domain switching process at different magnetic fields in a single-crystalline Fe/CoO bilayer grown on MgO(001) substrate. In spite of the zero-net magnetic moment in the CoO layer, we find that the activation energy barrier of CoO AFM domain switching decreased at larger magnetic field. To separate the different behaviors of domain nucleation and domain wall motion during the CoO spin switching process, a new analytical method was developed. Using this method, we found that the CoO domain nucleation energy barrier exhibited a jump at a critical magnetic field while the CoO domain wall motion experienced only a tiny energy barrier variation. The field-dependent behaviors of the energy barriers were attributed to the formation of a spiral domain wall in the Fe layer during its magnetization reversal and this was supported by micromagnetic simulations.

A novel method for calculating the energy barriers for carbon diffusion in ferrite under heterogeneous stress.

A novel method for accurate and efficient evaluation of the change in energy barriers for carbon diffusion in ferrite under heterogeneous stress is introduced. This method, called Linear Combination of Stress States, is based on the knowledge of the effects of simple stresses (uniaxial or shear) on these diffusion barriers. Then, it is assumed that the change in energy barriers under a complex stress can be expressed as a linear combination of these already known simple stress effects. The modifications of energy barriers by either uniaxial traction/compression and shear stress are determined by means of atomistic simulations with the Climbing Image-Nudge Elastic Band method and are stored as a set of functions. The results of this method are compared to the predictions of anisotropic elasticity theory. It is shown that, linear anisotropic elasticity fails to predict the correct energy barrier variation with stress (especially with shear stress) whereas the proposed method provides correct energy barrier variation for stresses up to ∼3 GPa. This study provides a basis for the development of multiscale models of diffusion under non-uniform stress.

On switching field dependence of the thermally excited single domain particles

Analysis of the characteristic dependency of the switching field distribution of a system of noninteracting single domain particles was conducted based on the bi-state, nonequilibrium probabilistic approach. The analysis was carried out as a function of applied field orientations, transition energy barrier variation, and in combination with a given distribution of the particle size and anisotropy constant, under the influence of thermal relaxation. The concept of the blocking temperature that the energy barrier being approximately equal to /spl sim/25 k/sub B/T was shown to be invalid unless the period of the field sweep is /spl sim/1 h.