Number Of Resonance Peaks Research Articles

Stability and Spin Waves of Skyrmion Tubes in Curved FeGe Nanowires.

In this work, we investigate the influence of curvature on the dynamic susceptibility in FeGe nanowires, both curved and straight, hosting a skyrmionic tube texture under the action of an external bias field, using micromagnetic simulations. Our results demonstrate that both the resonance frequencies and the number of resonant peaks are highly dependent on the curvature of the system. To further understand the nature of the spin wave modes, we analyze the spatial distributions of the resonant mode amplitudes and phases, describing the differences among resonance modes observed. The ability to control the dynamic properties and frequencies of these nanostructures underscores their potential application in frequency-selective magnetic devices.

Effects of high-low frequency electromagnetic radiation on vibrational resonance in Hodgkin–Huxley neuronal system

In this paper, based on the Hodgkin–Huxley (H–H) neuron model, the effects of high-low frequency (HLF) electromagnetic radiation on vibrational resonance (VR) in a single neuron is investigated. It is found that VR can be observed in a single H–H neuron model with or without considering HLF electromagnetic radiation. However, HLF electromagnetic radiation can cause changes in the structure of the resonance peaks and make the maximum region and intensity of the response amplitude smaller, which weakens the VR in the neuronal system. This is because the HLF electromagnetic radiation makes the neuronal electrical activities less regular, resulting in weaker synchronization between input low-frequency signal and output firing. In addition, the effects of the system parameters such as the HF electromagnetic radiation amplitude on the Fourier coefficients are investigated, and it is found that these parameters can also cause changes in the number of resonance peaks, resulting in vibrational mono-resonance and vibrational bi-resonances. When the frequency of the HLF electromagnetic radiation is between 0.014 and 0.041, local anti-resonance can be also observed. This has practical significance in reducing some of the unexpected vibration in aerospace engineering and mechanical fields. The HLF electromagnetic radiation plays an important role in weakening the VR of neuronal systems. Therefore, this study could provide new insights to further control the abnormal electrical activities and information transmission of neurons, which can lead to better design and development of therapeutic programs for neurological disorders and neuroplasticity therapies, and advance neuroscience.

Wavelength multiplexing system based on ring resonators

Wavelength Division Multiplexing, WDM, is a technology developed for applications in telecommunications with the purpose of combining numerous wavelength signals into one single fibre. The aim of this research is the characterization of WDM systems of ring resonators with planar optical waveguides. The optical responses for different configurations, dimensions, and materials are analysed by doing a parametric study both considering analytical expressions and a Finite Element Tool. The results are from add-drop topologies with one, two and three rings. The main difference between topologies with the same parameters is the number of resonance wavelengths, which is higher due to the increase in the number of ring-shaped waveguides. It is concluded that adjusting the rings’ dimensions, the resonant wavelengths are tuned. Furthermore, the higher the rings’ radius the lower is the free spectral range, that can take values from 40 nm to 90 nm. Then, the number of resonant peaks in a wavelength range may change. Also, 1500–5000 describes the values computed for the quality factor, whereas the full width at half maximum varies within some units of nanometres. For models with different core materials, the higher transmittances decrease with lower core refractive indexes and the resonance width increases. These are new degrees of freedom to tune the response of the device that can definitely work as optical wavelength multiplexer, having losses from 20% to 40% considering the transmitted optical power.

Harnessing a Dielectric/Plasma Photonic Crystal as an Optical Microwave Filter: Role of Defect Layers and External Magnetic Fields.

We investigate the transmittance spectrum of a multichannel filter composed of dielectric (A) and plasma (P) materials in the microwave region within the transfer matrix formalism. Two configurations of the proposed filter are studied under the influence of an applied magnetic field: (1) a periodic structure containing (A/P)N unit cells surrounded by air and (2) the introduction of a second dielectric material (D) acting as a defect layer to produce an (AP)N/2/D/(AP)N/2 structure. Our findings reveal that in the periodic case, the number of resonant states of the transmittance increases with number N; however, the observed blue and red shifts depend on the intensity and orientation of the applied magnetic field. We present contour plots of the transmission coefficients that show the effect of the incident angle on the shifts of the photonic band gaps. Furthermore, we find that the introduction of a defect layer generates additional resonant states and merges the central resonant peak into a miniband of resonances. Moreover, we show that the number of resonant peaks and their locations can be modulated by increasing the unit cell number, N, as well as increasing the width of the inserted defect layer. Our proposed structures enable the design of novel photonic filters using magnetized plasma materials operating in the microwave region.

Effects of electric field on vibrational resonance in Izhikevich neuronal systems

In this paper, based on the Izhikevich neuron model, the effects of electric field (EF) on vibrational resonance (VR) of single neuron and bidirectionally coupled neurons system are investigated. It is found that multiple vibrational resonances (MVR) can be observed in a single Izhikevich neuron model whether EF is considered or not. After the introduction of EF, the system exhibits worse MVR and local vibrational anti-resonance can be observed. In coupled neuronal system, the effect of bidirectional coupling causes MVR to disappear and the system only exhibits the phenomenon of VR. When EF is not considered, the vibrational anti-resonance is also observed. Interestingly, the introduction of EF weakens both VR and anti-resonance in the system. In addition, the effects of system parameters such as the EF strength controller and coupling strength on the Fourier coefficients are also investigated, and it is found that these parameters can also cause changes in the number of resonance peaks, resulting in vibrational bi-resonance and vibrational triple-resonance. The EF plays an important role in attenuating VR in neuronal systems. Therefore, this study can provide new insights for further control of abnormal electrical activities and information transmission in neurons.

Static and Dynamic Magnetic Properties of Fe3O4 Nanotubes

In this paper, our objective was to investigate the static and dynamic magnetic properties of Fe3O4 nanotubes that are 1000 nm long, by varying the external radius and the thickness of the tube wall. We performed a detailed numerical analysis by simulating hysteresis curves with an external magnetic field applied parallel to the axis of the tubes (along the z-axis). Our findings indicate that nanotubes with an external radius of 30 nm exhibit non-monotonic behavior in their coercivity due to a change in the magnetization reversal mechanism, which was not observed in nanotubes with external radii of 80 nm. Additionally, we explored the dynamic susceptibility of these nanotubes and found that the position and number of resonance peaks can be controlled by manipulating the nanotube geometry. Overall, our study provides valuable insights into the behavior of Fe3O4 nanotubes, which can aid in the design and improvement in pseudo-one-dimensional technological devices.

Multilayer graphene-enabled structure based on Salisbury shielding effect for high-performance terahertz absorption.

Sandwich-type structure based on Salisbury screen effect is a simple and effective strategy to acquire high-performance terahertz (THz) absorption. The number of sandwich layer is the key factor that affects the absorption bandwidth and intensity of THz wave. Traditional metal/insulant/metal (M/I/M) absorber is difficult to construct multilayer structure because of low light transmittance of the surface metal film. Graphene exhibits huge advantages including broadband light absorption, low sheet resistance and high optical transparency, which are useful for high-quality THz absorber. In this work, we proposed a series of multilayer metal/PI/graphene (M/PI/G) absorber based on graphene Salisbury shielding. Numerical simulation and experimental demonstration were provided to explain the mechanism of graphene as resistive film for strong electric field. And it is important to improve the overall absorption performance of the absorber. In addition, the number of resonance peaks is found to increase by increasing the thickness of the dielectric layer in this experiment. The absorption broadband of our device is around 160%, greater than those previously reported THz absorber. Finally, this experiment successfully prepared the absorber on a polyethylene terephthalate (PET) substrate. The absorber has high practical feasibility and can be easily integrated with the semiconductor technology to make high efficient THz-oriented devices.

Magnetization enhanced the multiple magnetic domain-dominated resonance modes in stripe domain films

FeCoHf films with different Hf contents and thicknesses were deposited by composition-gradient sputtering. The results showed that the stripe domain (SD) structure emerges when the film thickness exceeds a critical thickness (220–330 nm), but the increase in introduced Hf leads to a decrease in magnetization, and in turn, the stripe phase weakens and eventually disappears. Dynamic measurements revealed magnetic domain-dependent resonant absorption spectra with up to seven resonance peaks, which have rarely been observed in magnetic film with an established SD structure. The number of resonant peaks can be controlled by the saturation magnetization of the film. Micromagnetic simulations indicate that multiple magnetic domain resonance modes can be attributed to the enhanced magnetization, which induces an increase in the magnetic domain wall volume. These results emphasize the pivotal role of magnetic domain dynamics in the framework of spintronic and microwave devices.

Experimental investigation on minimizing degradation of solar energy generation for photovoltaic module by modified damping systems

With the rapid increase in solar energy generation, it is common to see solar photovoltaic modules mounted on structures subjected to dynamic loading. These dynamic loads induce vibration in solar photovoltaic modules, which generate cracks and micro-cracks. This deteriorates the solar photovoltaic modules' performance and life, effectively reducing solar energy generation. In this context, this paper deals with modal and harmonic response analysis of solar photovoltaic modules. The photovoltaic module's natural frequencies and mode shapes for ten different mounting configurations are determined using the composite plate Finite Element Model for three separate solar photovoltaic technologies. The finite element model is validated by comparing it with experimental and published results. Acceleration, velocity and displacement responses are determined in harmonic response analysis for base excitation and body acceleration inputs separately. Moreover, harmonic response analysis is performed, for which the amplitude and Frequency of induced vibrations are decided based on measured metro train vibrations levels in the vicinity of the metro rail. It is observed that mounted natural frequencies are considerably affected by the mounting configuration. A comparison of first mode natural frequency between the first and last mounting configurations shows a difference of 214.9%. Harmonic response analysis gives the resonant acceleration, velocity and displacement peak levels for all ten mounting configurations. Based on the least number of resonant peaks and lower value of response amplitudes, the best and worst mounting configurations are identified for all three solar photovoltaic technologies. This study provides a basis for selecting the best mounting arrangements to achieve the best solar energy conversion efficiency with minor degradation of the solar photovoltaic modules subjected to induced vibrations.

Acoustic modeling of honeycomb structures for second load direction with damping consideration

The control of low-frequency noise in buildings has become a critical issue because of the inadequate sound insulation in low frequencies (<200 Hz) for most partitions and doors. In the present study, an analytical model has been proposed to specify the relationship between the acoustic parameters such as acoustic impedance of honeycomb and the honeycomb geometry. In this regards, three materials (Polycarbonate, Polypropylene, and Polyurethane), seven angles (45°, 30°, 15°, 0°, −15°, −30°, −45°), and three cell arrangement (1 × 1, 2 × 2, and 3 × 3) were considered to find out the effect of these parameters on the sound absorption coefficient. Sound absorption in the frequency range of 1–500 Hz for angles of 45°, 30°, 15°, 0°, −15°, −30°, −45° was demonstrated using MATLAB software. A comparison of the results showed that the greater the angle’s absolute value, the more the sound absorption coefficient. By comparing all three materials’ absorption coefficient values, it was concluded that the 1 × 1 arrangement had greater absorption than the 2 × 2 and 3 × 3 arrangements. Also, the number of resonance peaks of polyurethane material for all angles was greater than the others in the same frequency range. Then, the panel with the honeycomb core of Polyurethane and 1 × 1 arrangement was recommended for cells with an internal angle of −45° in the present research case study for having more sound absorption.

Influence of curvature on the dynamical susceptibility of bent nanotubes

In this work we analyze the influence of curvature on the dynamic properties of the magnetization in bent nanotubes. Our results show that both the resonance frequencies and the number of resonant peaks have a strong dependence on the ground state of the magnetization created by the curvature. Our results can be understood from the analysis of the effective anisotropy and the Dzyaloshinskii–Moriya interaction (DMI) induced by curvature. The ability to control the dynamic properties of these curved ferromagnets makes them excellent candidates for developing applications based on resonant modes of spin waves.

Enhanced vibrational resonance by an amplitude modulated signal in a nonlinear dissipative two‐fluid plasma model

AbstractThe phenomenon of vibrational resonance is studied in a nonlinear dissipative two‐fluid plasma model with an asymmetric single‐well and double‐well potentials driven by an amplitude modulated (AM) signal. The external signal consisting of a low‐frequency () component and two high‐frequencies () and () components with . First, the approximate analytical expression for the response amplitude Q at the low frequency is obtained by means of direct separation of the slow and fast motions. We verified the theoretical results by numerical simulation using fourth‐order Runge–Kutta method and found it is in good agreement with the theoretical analysis. We show the enhanced response amplitude at the low frequency , showing more number of resonance peaks, a non‐decay of the response amplitude and hysteresis, and a jump phenomenon on the response amplitude curve due to the AM signal. In addition, we studied the effect of nonlinear dissipation on the response amplitude curve. By exploring the phase portrait and the bifurcation diagram, we explain the resonance mechanism and account for the other features of the resonance curve.

Ferromagnetic resonance in a microtube

Ferromagnetic resonance fields in a microtube with various ratios of the inner and outer diameter of the tube β were studied using micromagnetic simulation. For β<0.15, the resonance field agrees with the prediction of the Kittel equation for an infinite ferromagnetic cylinder for both parallel and perpendicular orientation of the applied field to its axis. For β>0.15, the resonance field increases from the resonance field of the infinite cylinder and approaches the level of a film magnetized along the plane. This behavior only qualitatively agrees with the prediction made using the calculated demagnetizing factor in the ferromagnetic tube. For β>0.15 and the applied transverse field, a number of resonance peaks were observed for the microtube with the outer diameter of 500 nm, but for nanotubes with the diameters of 50 and 100 nm, a single peak was observed.

Simplified Design of Quad-Band Terahertz Absorber Based on Periodic Closed-Ring Resonator

Multiple-band metamaterial absorbers as an important branch of metamaterial-based resonant devices have shown considerable application prospects in real life. However, current designs have many shortcomings in the realization of multiple-band absorption, including complex pattern structure, time-consuming fabrication steps, and strong interaction between sub-elements. Herein, a simple design of multiple-band metamaterial absorber based on single metallic resonator is presented. Basic cell of the multiple-band absorption is formed by a square metallic patch (cut by a concentric air gap) placed on a metallic mirror separated by an insulating medium material. The metamaterial structure can interact strongly with the incident beam to produce the fundamental mode resonance, third-order resonance, and two other resonances resulted from the concentric air gap introduction. The combining effect of the four discrete resonance modes provides the ability to achieve quad-band absorption. The quad-band absorption shows great dependence on the structure dimensions. Based on this, we further design a kind of multiple-band absorption having the adjustable number of absorption peaks by introducing photosensitive silicon material in the initial area of the air gap. The number of resonance peaks can be tuned flexibly from quad-band absorption to dual-band absorption by changing the conductivity (i.e., material property) of photosensitive silicon material.

Anionic Doping and Cationic Site Preference in CaYb4Al2Sb6- xGe x ( x = 0.2, 0.5, 0.7): Origin of the Enhanced Seebeck Coefficient and the Structural Transformation.

Three Zintl phase compounds belonging to the CaYb4Al2Sb6- xGe x ( x = 0.2, 0.5, 0.7; nominal compositions) system with various Ge-doping contents were successfully synthesized by arc-melting and were initially crystallized in the Ba5Al2Bi6-type phase (space group Pbam, Pearson codes oP26). However, after post-heat treatment at an elevated temperature, the originally obtained crystal structure was transformed into the homeotypic Ca5Ga2Sb6-type structure according to powder and single-crystal X-ray diffraction analyses. Two types of crystal structures share some isotypic structural moieties, such as the one-dimensional anionic chains formed by ∞1[Al2Sb8] and the void-filling Ca2+/Yb2+ mixed cations, but the slightly different spatial arrangements in each unit cell make these two structural types distinguishable. This series of title compounds is originally investigated to examine whether anionic p-type doping using Ge can successfully enhance thermoelectric (TE) properties of the Yb-rich CaYb4Al2Sb6- xGe x series even after the phase transition from the Ba5Al2Bi6-type to the Ca5Ga2Sb6-type phase. More interestingly, we also reveal that the given structural transformation is triggered by the particularly different site-preference of Ca2+ and Yb2+ among three available cationic sites in each structure type, which is significantly affected by thermodynamic conditions of this system. Band structure and density of states analyses calculated by density functional theory using the tight-binding linear muffin-tin orbital method also prove that the Ge-doping actually increases band degeneracies and the number of resonant peaks near the Fermi level resulting in the improvement of Seebeck coefficients. Electron localization function analyses for the (0 1 0) sliced-plane and the 3D isosurface nicely illustrates the distortion of the paired-electron densities due to the introduction of Ge. The systematic TE property measurements imply that the attempted anionic p-type doping is indeed effective to improve the TE characteristics of the title CaYb4Al2Sb6- yGe y system.

Quad-Spectral Perfect Metamaterial Absorber at Terahertz Frequency Based on a Double-Layer Stacked Resonance Structure

Development of multispectral perfect light absorbers for applications in biological sensing, spectroscopic imaging, and selective thermal emitters is urgently required. Unfortunately, current multispectral absorbers are typically only based on a combination of fundamental resonances of multiple resonators using the design concepts of a coplanar superunit structure or multiple vertically stacked layers, which does not introduce new resonances while such structures are difficult to fabricate. In this work, a type of quad-spectral absorber formed by a double-layer stacked resonant structure is presented and demonstrated. Numerical simulations show that the suggested structure can achieve near 100% absorption at four frequency bands. The quad-spectral absorption results from excitation of two sets consisting of the fundamental mode and third-order resonance of the designed structure. The suggested device is insensitive to the polarization of the incident light due to the high degree of symmetry of the resonance structure. Device parameters are investigated to further explore the physical origin of the quad-spectral absorption. Moreover, it is revealed that the number of resonance peaks can be further increased by employing one more layer.

Study of Surface-Enhanced Raman Scattering of Plasmonic Coupled Biomolecule: Role of Multi-Layered Nanosphere

In this communication, we study the surface enhanced Raman scattering (SERS) by a molecule which is adsorbed on a trilayer (Ag@SiO2@Ag) spherical shaped metallic nanostructure. We have studied the plasmonic signature of the trilayer nanostructure under quasi-static approximation. The plasmonic response of trilayer nanostructures is analysed in terms of surface plasmon resonances and extinction efficiency which is a function of size, shape of core-shell material and thickness polarisability. The polarisability of trilayer nanostructure has been derived using T-matrix method and coupled it with the Gersten-Nitzan model to study the Raman enhancement factor. The Raman enhancement factor (R) has been studied under the influence of several parameters such as core-shell material, thickness, molecule distance and the surrounding media. The model developed here suggests strong relative amplification of the Raman gain of biomolecule adsorbed on the surface of the nanogeometry. The trilayer metal nanostructure exhibits three plasmon resonance peaks in UV to visible range (Raman spectroscopy range) which helps in detection of biological molecules into three different regimes. We have also compared the Raman enhancement factor for trilayer, bilayer and single metal nanosphere and it was observed that the magnitude of Raman gain factor, number of resonant peaks and its spectral bandwidth are different for different geometries.

Field enhancement factors and self-focus functions manifesting in field emission resonances in scanning tunneling microscopy

Field emission (FE) resonance (or Gundlach oscillation) in scanning tunneling microscopy (STM) is a phenomenon in which the FE electrons emitted from the microscope tip couple into the quantized standing-wave states within the STM tunneling gap. Although the occurrence of FE resonance peaks can be semi-quantitatively described using the triangular potential well model, it cannot explain the experimental observation that the number of resonance peaks may change under the same emission current. This study demonstrates that the aforementioned variation can be adequately explained by introducing a field enhancement factor that is related to the local electric field at the tip apex. The peak number of FE resonances increases with the field enhancement factor. The peak intensity of the FE resonance on the reconstructed Au(111) surface varies in the face-center cubic, hexagonal-close-packed, and ridge regions, thus providing the contrast in the mapping through FE resonances. The mapping contrast is demonstrated to be nearly independent of the tip–sample distance, implying that the FE electron beam is not divergent because of a self-focus function intrinsically involved in the STM configuration.

Resonance transmission of one-dimensional quantum walk with phase defects

In this paper, the resonance transmission of discrete time quantum walk is studied when it walks on one-dimensional lattice in which two-phase defects or a piece of phase defects exists. The quasi energy of discrete time quantum walk has a unique dispersion relation with the momentum, from which we first discuss the wave velocity direction versus the values of momentum, and distinguish the incident wave and the reflected wave. The gap between two energy bands depends on the parameters of coincident operator, so the phase defects, which break down the translation invariance of quantum walk on uniform lattices, can be regarded as an analogue of quantum potential. Then we use the condition of energy conversion at the boundary points to obtain the transmission rate and discuss its variation with the incident momentum for different strengths and widths of defects in detail. The multiple resonant peaks are observed due to the enhanced interference effect. Different resonant behaviors are shown when the strength of defect is less or greater than /2, correspondingly the resonances occur in a wide region of incident momentum or the sharp resonant peaks appear at discrete values of momentum. Under the condition of strong defect strength, i.e., approaching to , the qualitative relation between the number of resonant peaks and the widths of defect region is given. The number of resonant peaks is 2(N-1) when the two phase defects are located at N sites symmetric about the origin, while the number is 2N when a piece of phase defects is located at -N to N sites. In the case of a piece of phase defects, we also present the phase diagram in parameter space of (k, ) to show the discrete time of quantum walk propagating or tunneling through the defect region. In terms of this phase diagram, the variations of transmission rate with the incident momentum are reasonably explained. One special phenomenon is that the quantum walk is almost totally reflected in the tunneling case except for =/2 and k being slightly off -/2. Moreover, this behavior seems little affecting the defect strength, just similar to a classical particle. As a result of this research, we hope to deepen the insight of the quantum walk and provide methods to control the spreading of quantum walk through artificial defects.

Thickness-Dependent Transmission in a Finite Photonic Crystal Containing Nearly Ferroelectric Superconductor

In this paper, anomalous transmission properties in a finite photonic crystal made of a nearly ferroelectric superconductor, and a dielectric have been theoretically investigated. We show that, in the thickness domain, the transmission spectrum can be divided into two different regions: nonresonance and resonance. There are resonant transmission peaks in the resonance region, and the number of peaks is strongly dependent on the number of periods. In the frequency response, the number of resonant peaks is also increased as the thickness of nearly ferroelectric superconductor increases. The appearance of anomalous peaks enables us to design a narrowband filter without introducing any defect layer into the photonic crystal.