Explore the vast range of titles available.

Directed transport of a deformable particle is numerically investigated in a two-dimensional periodic channel. Unlike the rigid particle, the deformable particle can pass through the channel bottleneck that is significantly smaller than the particle size. The deformable characteristics of the particle can greatly affect the directed transport of the particle. (i) For the case of active deformable particle, the self-propelled velocity can break thermodynamics equilibrium and induce the directed transport. The average velocity is a peak (or valley) function of the particle size for large (or small) self-propulsion speed. Particle softening (large shape parameter) facilitates the rectification of the particle for small particle, while it blocks the rectification for large particle. (ii) For the case of passive deformable particle, periodic oscillation of the particle size can also break thermodynamical equilibrium. There exists an optimal oscillating frequency at which the average velocity takes its maximal value. For low oscillating frequency, the average velocity is a peak function of the oscillating amplitude, while for high oscillating frequency the average velocity increases monotonically with the oscillating amplitude. Our results may contribute to the understanding of the transport behaviors of soft, deformable matter in confined structures.

In this monograph, we review the theory and establish new and general results regarding spreading properties for heterogeneous reaction-diffusion equations: The characterizations of these sets involve two new notions of generalized principal eigenvalues for linear parabolic operators in unbounded domains. In particular, it allows us to show that

We investigate sound propagation in lossy, locally resonant periodic structures by studying an air-filled tube periodically loaded with Helmholtz resonators and taking into account the intrinsic viscothermal losses. In particular, by tuning the resonator with the Bragg gap in this prototypical locally resonant structure, we study the limits and various characteristics of slow sound propagation. While in the lossless case the overlapping of the gaps results in slow-sound-induced transparency of a narrow frequency band surrounded by a strong and broadband gap, the inclusion of the unavoidable losses imposes limits to the slowdown factor and the maximum transmission. Experiments, theory, and finite element simulations have been used for the characterization of acoustic wave propagation by tuning the Helmholtz/Bragg frequencies and the total amount of loss both for infinite and finite lattices. This study contributes to the field of locally resonant acoustic metamaterials and slow sound applications.

The dispersion relation for the bulk magnetic polaritons is investigated in Fibonacci quasi-periodic structures. The quasi-periodic system, including the alternating layers of magnetic and non-magnetic mediums, is immersed in an external magnetic field. We found that the quasi-periodic structures (based on the Fibonacci series) improve the wave frequency of the magnetic polaritons compared to a similar periodic structure. It is shown that the allowable bands show an increase in a quasi-periodic system. We can employ such quasi-periodic structures in the new electronic applications based on multi-band filtering systems.

A spatial modes filtering (SMF) finite-element time-domain (FETD) method with periodic boundary condition (PBC) is proposed for efficiently analyzing the electromagnetic characteristics of 3-D periodic structures with partial fine structures. The system matrices of FETD become asymmetrical because of the introduction of PBC, which prevents the system eigenvalue analysis. By decomposing the system matrix into PBC-independent and PBC-related parts, the unstable spatial modes under the given large time step can be found and removed from the symmetrical PBC-independent system matrices. Then the system matrix equation and time marching of the SMF-FETD and SMF-FETD method based on local eigenvalue solution (LES-SMF-FETD) with PBC are obtained. Numerical results illustrate the efficiency and effectiveness of the SMF-FETD method with PBC based on non-uniform mesh for analyzing the transport properties of 3-D periodic structures.

Reciprocity is a fundamental property of wave propagations, and many researchers devoted their efforts to breaking the reciprocity and implementing unidirectional wave propagations. At present, the main method to realize non-reciprocal waves uses aperiodic structure as the wave propagation medium. The non-reciprocal bandgap achieved by this method is narrow and difficult to adjust actively. To improve the controllability of non-reciprocal bandwidth, a one-dimensional (1D) periodic lattice structure based on linkage element is proposed in the work. The linkage element enables the lattice structure to have nonlinear stiffness with respect to the asymmetry of the equilibrium position. This stiffness asymmetry leads to the non-reciprocity of wave propagation, which provides a new idea for the design of non-reciprocal structures. To deal with the strong nonlinearity and high dimensional characteristics of the structure, the improved incremental harmonic balance (IHB) method is used to analyze the dispersion and bandgap characteristics of the structure. The results show that the structure has two bidirectional bandgaps (high and low frequency) and four unidirectional bandgaps, and the position, width and direction of the bandgap can be adjusted by the equilibrium position and mechanical parameters of the structure. The obtained structural properties are verified by numerical experiments.

Motivated by the observations of Voyager 1 and 2 spacecraft and Freja satellite observations in Saturn’s magnetosphere, the formation of dust-acoustic (DA) localized and periodic waves in a complex plasma having superthermal electrons and ions are reported. In this regard, a modified Kadomtsev–Petviashvili (mKP) equation is derived by employing the weak turbulence theory for studying the characteristics of the nonlinear dust-acoustic waves (DAWs) in the model under consideration. The localized and periodic wave solutions to the mKP equation are derived using ansatz method in terms of Jacobi elliptic functions (JEFs). It is reported that the phase velocity of the DAWs in the Saturn’s magnetosphere is lower for kappa distributed ions and electrons by comparison with regions of space plasmas where the electrons and ions follow the Maxwellian distribution. The conditions for the existence of both localized and periodic waves are also presented. Estimates are also given of the spatial scales over which the dust-acoustic solitary/periodic structures form in Saturn’s magnetosphere.

Among composites, we can distinguish periodic structures, biperiodic structures, and structures with a functional gradation of material properties made of two or more materials. The selection of the composite’s constituent materials and the way they are distributed affects the weight of the composite, its strength, and other properties, as well as the way it conducts heat. This work is about studying the temperature distribution in composites, depending on the type of component material and its location. For this purpose, the Tolerance Averaging Technique and the Finite Difference Method were used. Differential equations describing heat conduction phenomena were obtained using the Tolerance Averaging Technique, while the Finite Difference Method was used to solve them. In terms of results, temperature distribution plots were produced showing the effect of the structure of the composite on the heat transfer properties.

A microstructure determines macro functionality. A controlled periodic structure gives the surface specific functions such as controlled structural color, wettability, anti-icing/frosting, friction reduction, and hardness enhancement. Currently, there are a variety of controllable periodic structures that can be produced. Laser interference lithography (LIL) is a technique that allows for the simple, flexible, and rapid fabrication of high-resolution periodic structures over large areas without the use of masks. Different interference conditions can produce a wide range of light fields. When an LIL system is used to expose the substrate, a variety of periodic textured structures, such as periodic nanoparticles, dot arrays, hole arrays, and stripes, can be produced. The LIL technique can be used not only on flat substrates, but also on curved or partially curved substrates, taking advantage of the large depth of focus. This paper reviews the principles of LIL and discusses how the parameters, such as spatial angle, angle of incidence, wavelength, and polarization state, affect the interference light field. Applications of LIL for functional surface fabrication, such as anti-reflection, controlled structural color, surface-enhanced Raman scattering (SERS), friction reduction, superhydrophobicity, and biocellular modulation, are also presented. Finally, we present some of the challenges and problems in LIL and its applications.

Terahertz (THz) plasmonic metamaterial, based on a metal-wire-woven hole array (MWW-HA), is investigated for the distinct power depletion in the transmittance spectrum of 0.1–2 THz, including the reflected waves from metal holes and woven metal wires. Woven metal wires have four orders of power depletion, which perform sharp dips in a transmittance spectrum. However, only the first-order dip at the metal–hole–reflection band dominates specular reflection with a phase retardation of approximately π. The optical path length and metal surface conductivity are modified to study MWW-HA specular reflection. This experimental modification shows that the first order of MWW-HA power depletion is sustainable and sensitively correlated with a bending angle of the woven metal wire. Specularly reflected THz waves are successfully presented in hollow-core pipe wave guidance specified from MWW-HA pipe wall reflectivity.