Multiple Resonant Peaks Research Articles

Spatiotemporal resonance in mouse primary visual cortex

Human primary visual cortex (V1) responds more strongly, or resonates, when exposed to ∼10, ∼15-20, and ∼40-50Hz rhythmic flickering light. Full-field flicker also evokes the perception of hallucinatory geometric patterns, which mathematical models explain as standing-wave formations emerging from periodic forcing at resonant frequencies of the simulated neural network. However, empirical evidence for such flicker-induced standing waves in the visual cortex was missing. We recorded cortical responses to flicker in awake mice using high-spatial-resolution widefield imaging in combination with high-temporal-resolution glutamate-sensing fluorescent reporter (iGluSnFR). The temporal frequency tuningcurves in the mouse V1 were similar to those observed in humans, showing a banded structure with multiple resonance peaks (8, 15, and 33Hz). Spatially, all flicker frequencies evoked responses inV1 corresponding to retinotopic stimulus location, but some evoked additional peaks. These flicker-induced cortical patterns displayed standing-wave characteristics and matched linear wave equationsolutions in an area restricted to the visual cortex. Taken together, the interaction of periodic traveling waves with cortical area boundaries leads to spatiotemporal activity patterns that may affect perception.

Resonant peak reduction of a rotor system based on gradually variable stiffness of supports with shape memory alloy springs

A novel method for reducing the resonant peak of a flexible rotor at critical speeds based on control of the gradual variable stiffness of supports (GVSS) using shape memory alloy (SMA) springs is presented in this paper. The resonance peaks of a rotor structure can be attenuated through the design of GVSS law. Firstly, the impact of GVSS on the rotor's critical speeds was analyzed, and the mechanical mechanism of vibration reduction based on GVSS was identified. Secondly, a rotor system with a single critical speed was used for simulation analysis and it was founded that the starting time to change support stiffness and the change rate were two critical factors that affect vibration reduction. Then, a further simulation was undertaken on a test rig designed with dynamic similarity of an aeroengine rotor having multiple supports and multiple critical speeds. The range of the variable stiffness with SMA springs’ supports and the control strategy of GVSS were investigated. Afterwards, the test rig was manufactured and assembled for testing and validation. To achieve rapid temperature changes for variation of the support stiffness, an innovative design utilizing the carbon fiber heating tubes and the liquid nitrogen sprays for heating and cooling of shape memory alloy springs was carried out. The test results indicate that using gradually variable stiffness of supports with SMA Springs can effectively reduce the multiple resonance peaks of a rotor, with a maximum suppression rate of 52.3 %. This verifies the feasibility of the method. It also indicates the potential for further engineering applications.

Vibration localization and reduction of double-plate structures

A thin plate-type resonator is attached to a host-stepped plate to achieve vibration localization and reduction in initial low-order global vibration modes. A semi-analytical method is proposed to analyze the free and forced vibrations of the double-plate structure, considering the geometric configuration's heterogeneity and discontinuity. The double plate structure is divided into several sub-plates for individual modeling, with admissible functions constructed for the displacements of each subdomain. These subdomains are then combined into a unified whole through displacement compatibility conditions. The no-orthogonality between global vibration and localized modes is determined using analytic mode functions obtained by the Ritz method with special admissible functions, which is crucial for suppressing the multiple resonance peaks of global vibration using the integrated plate-type resonator. An intriguing finding is that at the frequency veering point of global vibration modes and localized modes, the non-orthogonality can lead to two coupled global-localized modes that are similar to the initial localized mode, and the vibration of initial global modes can be mainly concentrated in the resonator region outside the plate during free vibration. For force vibration of the double plate, the initial resonance peak splits from one into two smaller resonance peaks due to the two coupled global-localized modes. Furthermore, the coupled global-localized mode allows for a substantial reduction in the host plate vibration while making a negligible impact on the total mass and global vibration frequency. This study presents a promising approach for reducing multimodal vibrations in lightweight structures.

Triple band diamond-shaped polarization insensitive plasmonic nano emitter for thermal camouflage and radiative cooling

This study proposes the design of a novel Metal-Insulator-Metal (MIM) nano-infrared emitter that uses a unique diamond-shaped grating to achieve selective infrared absorption. Diamond-shaped nano emitter (DNE) structure exhibits four narrow resonant peaks within key absorption windows such as short-wave infrared (SWIR) mid-wave infrared (MWIR), alongside with a wide absorption band in the Non-Transmissive Infrared Range (NTIR) for thermal camouflage applications compatible with radiative cooling. Moreover, the proposed DNE is polarization insensitive as it has an in-plane symmetric design. Using the 3D Finite-Difference Time-Domain (FDTD) simulations, we demonstrate the nanoantenna’s superior performance characterized by its high absorption rates and tuned effective impedance matching. As of our knowledge, the findings suggest that this is the first time that a MIM structure achieved multiple narrow resonance peaks, located in SWIR and MWIR simultaneously, with a wide absorption range in NTIR. Represented DNE stands as a significant innovation in the field of stealth technology, providing a tunable, high-efficiency solution for managing and controlling thermal emissions across diverse applications.

Random incidence sound absorption of micro-perforated panel absorbers backed with parallel-arranged cavities of different depths

This study investigates sound absorption performance of a kind of wideband micro-perforated panel (MPP) absorbers with parallel-arranged backing cavities at different depths in a diffuse field. An analytical prediction model is presented for evaluating the random incidence absorption coefficient of this type of absorbers, and it exhibits excellent agreement with finite element model and experimental measurements. Then, numerical cases were established using this model to investigate the absorption characteristics of this type of absorbers under random incidence, considering the influence of cavity depths and MPP parameters. Results show that the cavity depth and MPP perforation diameter in this absorber are primary influencing parameters controlling the overall sound absorption performance. Cavities at different depths introduce multiple resonant absorption peaks, while the perforation diameter determines matching conditions between the MPP and air impedance, which simultaneously broaden the absorption bandwidth of this MPP absorber. Although individually adjusting the panel thickness and perforation rate has a smaller impact compared to the perforation diameter, the interaction between these two parameters has significant influences across the entire absorption frequency band.

Broadband, thin thickness and low filling ratio microwave absorption by constructing Sm2Fe17/Fe(Sm) hard/soft magnetic nanoparticles in Sm2O3-doped porous carbon matrix

Exchange-coupled hard/soft magnetic composites are supposed to be promising microwave absorber, due to the multiple-resonance peaks in permeability. However, due to insufficient magnetization and dielectric loss, soft/hard ferrite magnets are difficult to achieve further breakthroughs in microwave absorption performance. In this work, the special hard/soft magnetic composites are successfully fabricated, in which Sm2Fe17/Fe(Sm) hard/soft hybrid nanoparticles are embedded in ∼5 nm Sm2O3-doped porous carbon matrix. The hard/soft magnetic exchange-coupling result in the multiple-resonance peaks beyond Snoek’s limitation at broad wave band and the Sm2O3-doped carbon supplements dielectric loss capacity. Multiple-resonance effect is modified by adjusting the ratio of hard and soft magnetic components and the dielectric loss capacity is supplemented by Sm2O3-doped carbon. Herein, the hard/soft magnetic exchange-coupling and dielectric matrix are dexterously integrated to achieve broad absorption band with thin matching thickness and low filling ratio. By varying the ratio of Fe3+/Sm3+ in raw material, 20 wt% Sm2Fe17/Fe(Sm)-paraffin composites can reach the maximum effective absorption bandwidth of 6.8 GHz with matching thickness of 1.6 mm, the minimal reflection loss of −47.15 dB with 1.5 mm and the optimal microwave absorption efficiency of 71.1 dB·GHz/mm with 1.4 mm. Overall, this work provides a simple approach to introduce multi-resonance effect, which broadens the path for advanced absorbers with broad band and thin thickness and low filling ratio.

Modulation effect of Zr-Sm co-doped on microwave absorption performance of barium ferrite

Zr-Sm co-doped barium ferrites BaFe12–2x(ZrSm)xO19(x = 0, 0.2, 0.4, 0.6) were successfully prepared by sol-gel method. The effects of Zr-Sm co-doped on phase formation, microscopic morphology, magnetic parameters, electromagnetic and microwave absorption properties of barium ferrite were studied. The results show that the saturation magnetization(Ms) of BaFe12–2x(ZrSm)xO19 first increases and then decreases, the coercivity(Hc) first decreases and then increases with the increase of doping amount(x) of Zr-Sm. Large grain size and sheet morphology lead to the transition of BaFe11.6(ZrSm)0.2O19 towards soft magnetic properties. The introduction of Zr-Sm increases the amount of oxygen vacancies, and dielectric loss value of material is obviously enhanced, this improves the polarization relaxation of materials. At the same time, multiple natural resonance peaks appeared in the virtual part of the permeability (μ"), which regulated the absorbing properties of samples. The best microwave absorption properties of sample is obtained when doping x = 0.2, at the thickness of 2.8 mm, the maximum reflection loss(RL) is − 51.75 dB. The effective absorption bandwidth (RL ≤ −10 dB) is 4.4 GHz, it covers almost all the X-band(8–12 GHz). Compared with existing doped barium ferrite, the material possesses a greater reflection loss and excellent prospects in the field of microwave absorption.

Discrimination of Brain Abscess and Necrotic Brain Tumor with Proton MR Spectroscopy and Diffusion-Weighted Imaging

Objective: To compare the efficacy of MR spectroscopy and diffusion-weighted imaging in discriminating between cystic or necrotic tumors and pyogenic brain abscesses.Study Design: A retrospective study design.Place and Duration of Study: The Study was conducted at the Radiology Department of Nishtar Hospital Multan and General Hospital Lahore, Pakistan, from January 2022 to January 2023. Methods: A total ten patients were included in the study. Of 10 patients, 5 had pyogenic abscesses, and 5 had tumors. Tumors were metastases (2 patients), glioblastomas (2 patients), and anaplastic astrocytoma (1 patient). Proton MR spectroscopy and diffusion-weighted imaging were performed in all patients. Results: Results showed that significant resonance lines (creatine/phosphocreatine, N-acetyl aspartate, and choline) observed in normal brain parenchyma were missing in abscesses or necrosis. MR spectroscopy of abscess showed multiple resonance peaks. Diffusion-weighted images showed that all pyogenic abscesses had lower ADC values and were hyperintense compared to normal brains. Conclusion: Diffusion-weighted imaging is more accurate and less time consuming method for discrimination of brain lesions compared to MR spectroscopy.
 How to cite this: Saqib HA, Asghar A, Firdous A, Zahra M, Islam Z, Mushtaq S. Discrimination of Brain Abscess and Necrotic Brain Tumor with Proton MR Spectroscopy and Diffusion Weighted Imaging. Life and Science. 2023; 4(4): 432-437. doi: http://doi.org/10.37185/LnS.1.1.431

A multi resonant wave-absorbing honeycomb sandwich structure with excellent electrical performance damage tolerance

Wave-absorbing honeycomb sandwich structure (HSS) is widely used in aviation equipment, playing an important role in the integration of load-bearing and stealth shielding. The high-intensity service of aviation equipment beyond design condition accelerates damage and complicates failure triggers. In this work, a decentralized construction strategy with multiple resonant absorption peaks is proposed to enhance the electrical performance damage tolerance (EDT) of wave-absorbing HSS in 4–18 GHz frequency band. The designed multi resonant absorption peaks for 30 mm thick wave-absorbing honeycomb with 1 mm thick SiO2 fiber reinforced epoxy resin (SiO2f/ER) composites as top and bottom panels occur in the vicinity of 5 GHz, 9 GHz, 13 GHz, and 17 GHz, respectively. When the panel damage area accounts for 72 % or the penetrating damage area accounts for 18 %, the effective absorption bandwidth (EAB) of proposed HSS covers 4–18 GHz, indicating excellent EDT. By analyzing the normalized impedance, Smith chart, as well as power loss density, the excellent EDT is attributed to the pinning effect at each resonant frequency point, which benefits both impedance matching and electromagnetic wave (EMW) attenuation.

Terahertz narrow bandpass filters based on double-layer metallic woven meshes with engineered Fabry-Perot cavities

In this work, a new narrow bandpass filter based on double-layer metallic woven meshes (MWMs) is experimental and numerically investigated. Differing from generally reported 2D planar structures, the MWM is a 3D structure consisting of metal cross-bending wires. Multiple resonant peaks with high isolation originating from the Fabry-Perot cavities are achieved by changing the distance between two MWM layers. Simulated results show that an optimized double-layer MWMs presented a sharp resonant peak whose full width at half maximum is narrower than 1.25 GHz. The achievement of such filters based on the engineered Fabry-Perot cavity would provide a new method for the design of ultra-narrowband filters and ultra-sensitive sensors in terahertz regions.

A Study of Plasmonic Properties of a Rhodium I-shaped Nanomaterial

In this work, the optical properties of a rhodium I-shaped nanomaterial are studied. In the UV-visible regime, the scattering efficiency and the electric field are calculated via the finite-difference time-domain method, with the parameters varying including the height, the length ratio, and the polarization of the incident light. The results show that multiple resonance peaks are observed in the scattering spectrum in the ultraviolet region, corresponding to different electromagnetic modes. It is also revealed that the peak strength of the nanostructure can be effectively tuned by adjusting the structural parameters. The proposed rhodium nanomaterial may provide a theoretical basis for the design of optical devices in the ultraviolet regime. The obtained results provide useful guidance for the implementation of nanoantenna and fluorescence enhancement, etc.

Study on nonlinear dynamic characteristics of power six-branch herringbone gear transmission system with 3D modification

The power six-branch herringbone gear transmission system has the advantages of large power transmission and transmission ratio. Because of its multi-way transmission and over-constraint structure, to prevent loaded tooth interference, there are large backlashes between teeth. The system shows complex nonlinear dynamic characteristics under the influence of backlashes, which seriously affects meshing performance. The modification technology can effectively improve gear meshing performance. Hence, on the basis of optimizing meshing performance of the active pair of the six-branch herringbone gear transmission system, this article will combine 3D modification with system nonlinear vibration characteristics and propose an analysis method of the system nonlinear vibration characteristics under 3D modification to reduce vibration and noise. First, the 3D modified tooth surface equation is determined by forming grinding, the loaded transmission error (LTE) of the system's active pair is obtained by tooth contact analysis (TCA) and loaded tooth contact analysis (LTCA) technology, and the optimal modification parameters are obtained by Ant Lion Optimizer (ALO) with the minimum error amplitude as optimization objective. Then, the time-varying meshing stiffness of system under the optimal modification is calculated, and the pure torsional nonlinear dynamic model with backlashes, meshing stiffness, and static transmission error (STE) is established. Finally, the global vibration characteristics in parameter field are studied through time domain and bifurcation diagram of system. Results show that the 3D modification can eliminate edge contact of tooth and improve tooth contact performance. With the increase of input power, the root mean square (RMS) values of acceleration increase and the RMS values and jump decrease after 3D modification. With the increase of input speed, the RMS curves appear multiple resonance peaks and jumps at low input speed. After 3D modification, the RMS, jump, and resonance peak values decrease. Compared with level І, the backlashes and STEs of level II and phase difference ϛsII have great influence on system dynamic characteristics and easily make system in chaotic motion, while the 3D modification reduces their influence and makes system motion periodic.

Numerical modelling of acoustic metamaterial made of periodic Helmholtz resonator containing a damping material in the cavity

Acoustic metamaterials are frequently used in many fields such as aerospace, buildings and ground transportation industries for low frequency noise control applications. Different solutions based on membrane or Helmholtz resonators have been investigated in the past few years. In the present study, a numerical design of acoustic metamaterial made of Helmholtz resonator with a membrane in its cavity is presented. The resonator with a neck extended into the cavity is periodically embedded within a porous material. The membrane inside the resonator cavity is modelled as a linear isotropic elastic material with free and fixed boundary conditions. The transmission loss (TL) of the proposed metamaterial design, predicted by finite element method presents multiple resonant peaks while only one peak is obtained with a conventional resonator. Two TL resonance peaks are observed when the membrane circumferential boundary is free inside the resonator cavity. For fixed boundary conditions, more than two resonance peaks are obtained. The proposed metamaterial design can therefore be used in many industrial applications for low frequency noise attenuation.

A Hybrid Piezoelectric and Electromagnetic Broadband Harvester with Double Cantilever Beams

Vibration-energy harvesting is an effective strategy for replacing batteries and provides a long-term power supply to microelectronic devices. Harvesting vibration energy from human motions has attracted research attention in recent years. Here, a novel low-frequency hybrid piezoelectric and electromagnetic broadband harvester is proposed. Two parallel piezoelectric cantilever beams support the harvester and capture environmental vibration energy based on the piezoelectric effect. A permanent magnet is connected by springs to the two beams, and a fixed coil surrounds the moving permanent magnet, enabling energy conversion via the electromagnetic effect and the proof mass. The parameters influencing the output power of the harvester are optimized numerically to boost the harvester's performance. The output power of the proposed hybrid harvester is compared with that of a piezoelectric harvester and an electromagnetic harvester. The simulation results show that the output power is significantly higher for the hybrid harvester than for the piezoelectric and electromagnetic harvesters, and the bandwidth is broader owing to the double cantilevers. An experiment is conducted using a prototype of the hybrid harvester to evaluate its output power. The results show multiple resonant peaks, an extended bandwidth, and a maximum power of 6.28 mW. In contrast, the maximum harvested power of the piezoelectric harvester is only 5.15 mW at 9.6 Hz.

Coherent excitation energy transfer processes in two-dimensional para-sexiphenyl molecular clusters

Excitation energy transfer is one of the most important factors affecting the applications of para-sexiphenyl devices. The study of exciton dynamics and exciton coherence effect of para-sexiphenyl clusters under external field excitation is important in order to improve the performance of molecular devices composed of para-sexiphenyl and its related derivatives. In this work, the two-dimensional disc-like para-sexiphenyl molecular cluster is used as the object of study. The molecular system is simplified into a two-level model based on its structural features and energy level distribution. Within the framework of density matrix theory, the exciton dynamics and exciton coherence behavior of disk-like para-hexaphene molecular clusters excited by different pulse fields are analyzed through using the mathematical mean value approximation of the operator. The results show that when long pulses are used to excite para-sexiphenyl clusters, the single exciton state characteristic appears and is insensitive to the change of excited external field strength. When the clusters are subjected to strong pulsed fields with short pulse widths, multiple excitons are excited simultaneously in the cluster, forming multiple exciton states, with the exciton energy levels shifting toward lower energy and new hybrid states appearing. In the optical response spectrum, there appear multiple resonance peaks. And as the pulse field is enhanced, the multi-exciton effect becomes apparent and the hybridization energy level increases. Under short pulse excitation, the excited states are distributed differently in different energy regions, but all of them show obvious symmetry. As the highest-energy exciton states of H-type clusters are preferentially excited, we analyze the exciton state population and the exciton coherence evolution with time in the high-energy exciton state. With the pulse field increases, Rabi oscillations appear and the exciton coherence effect increases. When the pulsed field reaches a certain field strength, the exciton oscillation cooperativity disappears in the first 100 fs, showing the non-local characteristic. The position of the wave trough of the exciton state population corresponds to the peak in the exciton coherence size. It indicates that when the pulse field is intense enough, a large number of molecules are in the exciton coherent state during the pulsed excitation, and transient out-of-domain phenomena occur.

Experimental studies on nuclide identification radiography with a CMOS camera at Back-n white neutron source

As an advanced neutron imaging technique, nuclide identification radiography (NIR) using neutron resonance or cross-section differences is a promising technique for investigating nuclide spatial distribution inside samples. Since its proposal in 1980s, this technique has advanced very slowly due to many limitations in neutron source, detector efficiency and resolution. At the Back-n white neutron source at China Spallation Neutron Source, the NIR technique based on gated CMOS camera has been developed by taking the advantage of very high neutron flux and suitable energy spectrum of the Back-n neutron beam. Heavy nuclides, medium-mass nuclides and light nuclides have been tested to validate the effectiveness of the technique, covering the resonances from eV to MeV regions. Typical heavy elements such as Ag, In, Au and W, medium-mass elements such Al, Fe and Cu, light elements such as O have been used for experiments. The study shows, that nuclides with resonance peaks in the eV region can be easily identified, while the nuclides with resonance peaks above keV are difficult to be identified individually due to their narrow resonance peaks affecting the signal-to-noise ratio in the camera measurements. However, these nuclides can be differentiated for imaging by using adjacent multiple resonance peaks or distinct cross-section differences over wider energy ranges. The experiments are perhaps the first ones that demonstrate the NIR technique for the identification and imaging of nuclides with cross-section resonances covering from eV to several MeV.

Microwave Photonic Fiber Ring Resonator.

In this article, a new concept of microwave photonic (MWP) fiber ring resonator is introduced. In particular, the complex transmission spectra of the resonator in the microwave domain, including magnitude and phase spectra, are measured and characterized. Multiple resonance peaks are obtained in the magnitude spectrum; rapid variations in phase near resonance (i.e., enhanced group delay) are observed in the phase spectrum. We also experimentally demonstrate that the MWP fiber ring resonator can be potentially employed as a novel optical fiber sensor for macro-bending and fiber length change sensing (strain sensing). The experimental results are in good agreement with theoretical predictions.

Mixed-Resolution High-Q Sensor Based on Hybridized Spoof Localized Surface Plasmons

Spoof localized surface plasmons (LSPs) have proven significant advantages in sensing and detection. In this work, we propose a high-Q-factor and high-sensitivity hybridized spoof LSP sensor and a mixed-resolution algorithm. The sensor consists of two concentric inner and outer LSP structures with corrugated rings coupled to each other. The achieved Q-factor is up to 178, and the sensing figure of merit (FoM) is up to 30. Moreover, a mixed-resolution algorithm, combined with multiple resonant peaks, is proposed to enhance the Q-factor and sensing FoM. This algorithm doubles the Q-factor and sensing FoM effectively. This mixed-resolution sensor has a wide range of application prospects in the field of high-frequency on-chip resonators and sensors.

The resonant acoustic signatures of lithic debitage

Acoustic methods to search for submerged archaeological sites have shown that concentrations of knapped flint produce a visible acoustic response in chirp sonar profiles in a variety of geographical settings. Field tests and simulations have suggested that the submerged lithic signal is due to acoustic resonances of the flaked stone. We model and measure the resonant acoustic signatures of chert, obsidian, metavolcanic, and granitic lithic debitage. Struck lithics produce multiple resonant peaks under 30 kHz, with high quality factors that decrease with material coarseness. We use a combination of the finite element and boundary element methods to model the natural vibrations of lithic debitage in both air and water. Direct measurement of lithic material density and adjustment of the Young’s modulus and Poisson’s ratio provide excellent correspondence between measured and modeled resonances. Using a coupled finite element and boundary integral method, we model the acoustic scattering return of individual lithics in water as a function of frequency and incidence angle. We find the strongest resonant signal between 8 and 16 kHz for a collection of lithic debitage. Results indicate that the lithic resonance signal is highly directional, with target strength up to −20 dB when excited at optimal angles. For a flat-laying lithic, target strength at normal incidence is, on average, 10 dB lower than the strongest signal, typically found 55°±18° from normal incidence. We suggest that the best way to detect submerged lithics may not be through standard mono-static sub-bottom profiling with a direct downward pulse, but with a chirp pulse sent and received at an angle with respect to the sea bottom.

Design of multiple tuned mass damper devices and application to response control of bridge under external force

This article proposes a method for optimizing multiple tuned mass damper (TMD) devices for reducing bridge vibration as a vehicle passes over it. The method can design multiple TMD parameters simultaneously for different modes contributing to multiple resonance peaks. Moreover, the study analyzed the vibration of bridges with uncertain parameters. This study’s motivation is based on the optimal design of TMDs for bridge structures under external forces, such as the loads of moving cars and high-speed trains. In this case, the resonant response phenomenon can only happen at specific frequencies. The proposed optimization was developed based on the H 2 norm method to design the TMD parameters. The target of the present method is to minimize the response peaks around the resonance frequencies. Moreover, the contribution of the excited modes to each other at their resonance frequencies is considered. The TMD parameters were found to demonstrate good performance for reducing the vibration of bridges due to moving vehicles.