Frequency Dispersion Research Articles

High-entropy (Na0.2Bi0.2Ba0.2Sr0.2Zn0.2)TiO3 ceramics with enhanced energy storage density and reliable stability

High-entropy ceramics (HECs) have gained increasingly recent interest due to their fantastic physiochemical properties and rich compositions. The investigation of energy storage performance based on the temperature and frequency stability of HECs is still at an early stage, with limited reported studies. Here, we report lead-free (Na0.2Bi0.2Ba0.2Sr0.2Zn0.2)TiO3 (NBBSZT) HECs by a solid-state approach with a pressureless sintering process. X-ray diffraction (XRD) and scanning electron microscopy (SEM) studies demonstrate that NBBSZT HECs show a pure perovskite structure, uniform morphology and element distribution. Ferroelectric measurements indicate that the NBBSZT HECs exhibit an improved energy storage density of 1.03 J/cm3 and an efficiency of 77%, which is approximately 5 times and 17 times enhancement compared to Bi0.5Na0.5TiO3 (BNT) ceramics, respectively. The NBBSZT HECs also demonstrate excellent thermal stability and satisfactory frequency stability. More interestingly, the dielectric property studies show that the NBBSZT HECs exhibit frequency dispersion and diffuse phase transition. Temperature-dependent dielectric measurements indicate that the NBBSZT HECs exhibit better relaxor characteristics than that of BNT ceramics. These studies reveal that the high-entropy strategy provides a potential platform for designing ferroelectric ceramics.

Effects of the strain gradients on the band structures of the elastic waves propagating in 1D phononic crystals: An analytical approach

In this paper, an analytical method is proposed for the analysis of the effects of the strain gradients on the frequency band structures and band-gaps of the elastic waves propagating in one-dimensional (1D) nano-sized phononic crystals (PCs). The considered 1D nano-sized PCs are made of periodic unit-cells containing a metal section and an epoxy section. The strain gradients are taken into account to obtain the governing equations by using the strain energy, the kinetic energy and the Hamilton's principle. An analytical solution based on the transfer matrix method is derived to compute the frequency dispersion curves or band structures of the elastic waves. The continuity conditions on the interface between the neighboring sections and the periodic boundary conditions for the unit-cell are satisfied using the proposed analytical method. Two band-gap characteristics, namely the starting frequency and the width of each band-gap, are defined and investigated. The effects of the small-scale parameters in the strain-gradient theory on the band structures and the band-gap characteristics are analyzed and discussed in detail. It is demonstrated that the strain gradients may significantly influence the frequency band structures and the band-gap characteristics of the elastic waves propagating in 1D nano-sized PCs.

Quenching-driven advancements in functional properties of high-temperature lead-free Sc, Ga modified 0.67BiFeO3-0.33BaTiO3 relaxor ceramics

The processing method is one of the most important deciding factors in the fabrication of BiFeO3–BaTiO3 (BF-BT) based piezoceramics because of the Bi2O3 volatization. It significantly influences the functional properties, including the piezoelectric coefficients, dielectric properties, and microstructure. This study presents a significant advancement in the realm of high-temperature lead-free piezoelectric ceramics in terms of understanding effects of processing method on functional properties. In this light, a novel ceramic solid-solution, 0.67{Bi(Fe0.97Ga0.03)1-xScxO3}-0.33(BaTiO3) with x ≤ 0.07, incorporating Scandium (Sc) and Gallium (Ga) modifications, was meticulously designed and synthesized. Impact of two distinct sintering methods, namely air quenching (AQ) and closed sintering (CS) on the structure and properties of the developed materials are investigated. X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) analysis verified the formation of pure perovskite phases with successful incorporation of Sc and Ga into the 0.67BF-0.33BT lattice. The FTIR analysis revealed a sharp absorptive band in the 590-604 cm−1 range, corresponding to the signature of stretching and bending vibrations of (Ti/Fe)O6 octahedra. Rietveld structure refinement confirmed the coexistence of pseudocubic (Pm-3m) and rhombohedral (R3c) phases in AQ samples, with predominantly pseudocubic phase, while CS samples closely approximated the pseudocubic phase. The microstructure of the samples exhibits small average grain size distribution (<2 μm). Temperature-dependent dielectric measurements show strong frequency dispersion in the dielectric permittivity with broadened transition peaks. The ferroelectric studies reveal low Pr and Ec values. These observations suggest a ferroelectric relaxor-like behavior of the developed materials. Moreover, the permittivity peaks maxima (Tm) temperature corresponding to CS samples for 0.04<x < 0.07 is less than 390 °C at 10 Hz while it is above 400 °C for AQ samples. The results of our study reveal that AQ samples exhibit superior electrical and ferroelectric properties as compared to the CS samples. The AQ samples demonstrate improvements in Tm (>400 °C), d33(∼35 pC/N), Pr (∼4–11 μC/cm2), PS (∼8–21 μC/cm2), Ec (∼13–25 kV/cm) with reduced dielectric loss, and a better dielectric constant over a wide temperature range.

Structure characters, and thermal evolution of electrical and elastic behaviors in xBi(Ni1/2Hf1/2)O3-(1−x)PbTiO3 solid solutions with a tetragonal-pseudocubic phase boundary

In this study, we synthesized solid solutions of xBi(Ni1/2Hf1/2)O3-(1 − x)PbTiO3 (xBNH-PT) with the aim of elucidating their phase boundary behaviors and the associated physical properties. A tetragonal (T) - pseudocubic (PC) phase boundary was confirmed at x = 0.38. For x = 0.36 and x = 0.37 with distinct tetragonal distortions, a spontaneous ferroelectric-relaxor transition was observed. The introduction of a T-PC phase boundary not only led to enhanced piezoelectric properties (d33 = 456 pC/N, x = 0.39) but also effectively suppressed the spontaneous ferroelectric-relaxor transition. Detailed analysis revealed that the local structure of the initial state in 0.39BNH-0.61PT remained tetragonal. After poling, a long-range tetragonal phase was formed from the short-range tetragonal clusters, with the c/a value of ∼1.01. Our observations of frequency dispersion strongly suggest the presence of local inhomogeneities, resulting in distinct poling effects on the dielectric and elastic behaviors of the material.

Effect of charge transfer on the first hyper-polarizability of N,N-dimethylaniline and julolidine: a DFT based comparative study.

Quantum mechanical calculations involving electron correlation, frequency dispersion, and solvent effects were carried out to examine the second-order nonlinear optical response ofvarious acceptor, X (-CF3, -CN, -NO2) substituted in N,N-dimethylaniline (DMA) and julolidine(JLD). Here, both DMA and JLD acts as donor and the three substituted groups, X (-CF3, -CNand -NO2) at the para position of both the ring systems as acceptor. The NLO response (βHRS) of -CF3 and -CN substituted DMA and JLD is relatively lower compared to DMA-NO2 andJLD-NO2. The charge distribution is found higher in case of -NO2substituted DMA and JLD (±443 and ±449) compared to their -CF3 or -CN substitution. Electronic characteristics such asUV-Vis absorption spectra, crucial excited state parameters and charge transfer contribution to βHRS have been used to explain the NLO parameter of DMA-X and JLD-X. Variation of theincident optical frequency of light shows fluctuation of βHRS value and highest values of βHRS are obtain at the λmax frequency of each compound. Solvent polarity variation study on βHRSshows that βHRS varies linearly with the Kirkwood-Onsagar dielectric factor (D). All computational studies have been carried out using density functional theory (DFT) based method. Since CAM-B3LYP based hybrid functional improves the asymptotic behavior of theexchange interaction by dividing into short-range and long-range components, first hyperpolarizability values in the present study were computed using DFT/ CAM-B3LYP/ 6-31G+(d,p) level oftheory.

Multifunctional Characteristics of BCTH:0.5% Sm3+ Ceramics Prepared via Hydrothermal Method and Powder Injection Molding

Briefly, 0.005-mol Sm3+-doped (Ba0.85Ca0.15)(Ti0.9Hf0.1)O3 ([(Ba0.85Ca0.15)0.995Sm0.005](Ti0.9Hf0.1)O3, BCTH:0.005Sm3+) lead-free ceramics were prepared via hydrothermal method and powder injection molding using paraffin and oleic acid as binders, and the effects of preparation method and sintering conditions on microstructure, dielectric behavior and optical properties were investigated. XRD Rietveld refinement reveals the coexistence of orthogonal, rhombohedral and tetragonal phases, in which the crystal structure and phase fraction are influenced greatly by sintering temperature and holding time. The ceramics present enhanced relaxor behavior and frequency dispersion phenomenon as compared with those prepared by the solid-state sintering method, and the diffusive index γ value is within 1.421–1.673. The transition mechanism and luminescence performance of BCTH:0.005 Sm3+ were analyzed by Blasse formula, photoluminescence spectrum and fluorescence lifetimes, where emission peaks show slight blueshift, fluorescence decay lifetime becomes shorter, electric multipole interaction dominates the energy transfer mechanism, and the down-conversion luminescence is one-photon absorption process. The CIE chromaticity color coordinate (0.4746, 0.5048), correlated color temperature 3134 K and color purity 93.58% are achieved, which reveals that the BCTH:0.005 Sm3+ ceramics express high quality yellow emission rather than orange-red light of the hydrothermal method synthesized nano-powder, and have potential application in optical field.

Propagation and reflection of thermoelastic wave in a rotating nonlocal fractional order porous medium under Hall current influence

This investigation relates to the research on Hall current on propagation and reflection of elastic waves through non-local fractional-order thermoelastic rotating medium with voids. The system is split up into longitudinal and transverse components using the Helmholtz vector rule. It is observed that, through the frequency dispersion relation four coupled quasi-waves exist in the medium. The rotating solid modifies the nature of purely longitudinal and transverse waves toward the quasi-type waves. All the propagating waves are dispersive as they depend upon angular frequency. The quasi-longitudinal wave qP and quasi-transverse wave qSV faces cut-off frequencies. The nonlocal parameter affect all the waves except the quasi void wave. Analytically, the reflection coefficients of the wave are computed using suitable boundary conditions. MATLAB software is used to perform numerical computations for a chosen solid material. The amplitude ratios and the speed of propagation of the wave are plotted graphically for rotational frequency, nonlocal, fractional order, and Hall current parameter. The significant effect of the physical parameters on the computed results has been observed. The cut-off frequency of the waves is also presented graphically. The energy conservation law is proved in the form of energy ratios. The earlier findings in the literature are obtained as special case in the absence of rotation, Hall current parameter and porous voids.

Data-Driven oriented diatomic doping strategy to customize frequency dispersion for considerable microwave absorption

The electromagnetic (EM) parameters are the key factors to decode the complex microwave absorption properties, including matching thickness, absorption bandwidth and intensity. Numerous works hence have been focused on optimizing EM parameters to reinforce the comprehensive absorption performance, while most of the adopted experimental means still remain in sporadic and random attempts. In this work, the data-driven approach is first employed to forecast that a fierce frequency-dispersion of permittivity is necessary for the broad absorption, and the appropriate magnetic component can mitigate this elusive trend of required permittivity. Oriented by the simulated results, the B/N diatomic doped C/Fe3C magnetoelectric composites are successfully constructed, aiming at the precise regulation of electronic properties to achieve these specially customized EM parameters by forming multi-polarization resonances. The results demonstrate that the introduction of N defects and B defects could enrich the types of dipole pairs (CN, C-B, CNB, vacancy, etc.) and thus activate multi-polarization behavior. The charge density differences calculated by the first-principle further demonstrate that the occupation of B for C bonded with Pyridinic-N and Pyrrolic-N contributes to intense polarization behaviors over the lower frequency range. As a result, excellent microwave absorption properties can be finally achieved with an effective absorbing bandwidth reaching 7.2 GHz at 2.1 mm, implying that the joint use of data-driven and doping engineering strategies to customize frequency dispersion characteristics provides precious guidelines for boosting microwave absorption performance.

Maxwell–Wagner Polarization and Mixed Ferromagnetic and Antiferromagnetic State in Eu2CoMnO6

Herein, the electrical and magnetic properties of polycrystalline Eu2CoMnO6 are explored. More specifically, based on transport, dielectric, and impedance measurements, a thermally activated dielectric polarization near room temperature is reported. The valence states of transition metals in the Eu2CoMnO6 sample are studied by measuring the X‐ray absorption spectra at both Co‐L2,3 and Mn‐L2,3 edges. Moreover, based on magnetization, X‐ray absorption spectroscopy, and X‐ray magnetic circular dichroism measurements, the coexistence of competing ferromagnetic and antiferromagnetic phases is probed. Dielectric measurement shows a large dielectric constant near room temperature along with a large frequency dispersion. The temperature‐dependent resistivity, Cole–Cole plot, and imaginary part of impedance confirm the semiconducting nature of Eu2CoMnO6. Temperature‐dependent magnetization shows a second‐order magnetic transition below 125 K. Isothermal magnetization versus magnetic field loop shows first‐order metamagnetic transition, driven by mixed magnetic state owing to the presence of antisite disorder and antiphase boundary.

Determining minimum number of valid days for accurate estimation of sedentary behaviour and awake-time movement behaviours using the ActivPAL3 in nursing home residents

IntroductionScarce evidence is available about the minimum number of valid days wearing the activPAL3 to obtain a precise estimate of sedentary behaviour (SB) and awake-time movement behaviours (ATMB) in nursing home (NH) residents. The study aimed to determine the minimum number of valid days required for accurately estimate SB and ATMB using the activPAL3 device in NH residents. It also investigated how the starting point of a day (the 24-h period) impacted reliability.MethodsParticipants wore an activPAL3 for 7 consecutive days. The data was classified in two-time blocks (00:00 Ante Meridiem (AM)—00:00 AM midnight vs 12:00 Post Meridiam (PM) -12:00 PM midday) and the sample was stratified into two groups according to their capacity to stand and walk, to examine if timing of sampling or physical functioning affected minimum wear time. SB, ATMB, sociodemographic, and health-related variables were collected. Sensitivity of the time-blocks were tested through the dispersion frequencies and differences between blocks through Kolmogorov–Smirnov test for normality; parametric variables through two-related means T-test and Wilcoxon test for non-parametric data. Reliability was assessed with the Cronbach's Alpha and the intra-class correlation coefficient (ICC), using a one-factor model estimating the reliability for each measurement day loading in the same latent factor.ResultsNinety-five NH residents (81.1% women; age = 85.8 ± 7.2 years) were included. The midnight block had higher reliability, sensitivity and no statistically significant differences between days were found. At least three consecutive days of monitoring were necessary to achieve a reliability of ICC ≥ 0.8 for those NH residents able to stand and walk and six days for those unable.ConclusionsNH residents who are able to stand and walk require a minimum of three consecutive days wearing the device, while those who are unable require at least six days due to their highly homogenous daily routines and sensitivity to PA events. Regardless of the activPAL3 recording start time, data processing should reference the midnight time block.

Modeling Plasmonics and Electronics in Semiconducting Graphene Nanostrips

In recent decades, both academia and industry have shown noteworthy interest in investigating the semiconducting properties of graphene. Nevertheless, the lack of a suitable bandgap in graphene has restricted its practical applications in the current semiconductor industry. To overcome this limitation, graphene micro/nano-strips have been actively explored. The focus of the present study centers on modeling the electronic and plasmonic characteristics of graphene strips with varying widths: 2.7, 100, 135 nm, and 4 m. This analysis is conducted at ultralow energies (0.3 eV, or ~73 THz). We employ conventional density functional computations to estimate the Fermi velocity of graphene, refining the results via the GW approximation. Utilizing the accurate Fermi velocity, we employ a semi-analytical model to explore the ground state and plasmon properties (frequency and dispersion) of these graphene strips. Notably, this approach effectively replicates the density of states observed in narrow experimental graphene nano-strips (2.7 nm) grown on Ge(001) and, similarly, reproduces the plasmon spectrum found in synthesized graphene microstrips (4 μm) on Si/SiO2. Interestingly, our study also offers insights into the potential application of this approach in comprehending the plasmon frequency and plasmon dispersion of graphene nano-strips (~135 nm) acquired through liquid-phase exfoliation. The outcomes of this investigation present compelling evidence that the properties of graphene-based strips can be customized to fulfill specific requirements and applications. These findings hold significant promise for advancing graphene-based technologies, bridging the gap between fundamental research and tangible applications. Doi: 10.28991/ESJ-2023-07-05-01 Full Text: PDF

Bidirectional periodic pore structure Si-C-N multiphase ceramic with high thermostability and excellent microwave absorption properties over a wide temperature range

High-temperature electromagnetic wave (EMW) absorption materials are urgently needed for high thrust-to-weight ratio aero-engine. A novel EMW absorbing Si-C-N ceramic at elevated temperatures was fabricated by chemical vapor infiltration (CVI) Si3N4 and SiC on 2D plain carbon fiber preform forming periodic framing and then oxidation to remove carbon fiber. The three-level gradient periodic microstructure was in-situ constructed in the Si-C-N ceramics to meet the impedance matching characteristics and effectively attenuate as much as EMWs. Compared with traditional EMW absorption materials, the Si-C-N ceramics with bidirectional periodic pore had a lower density of 1.2 g/cm3 and better frequency dispersion behavior which could obtain an effective absorption bandwidth (EAB) covering the whole X-band at 2.45 mm and the lowest reflection coefficient (RCmin) of − 40 dB at 3.5 mm. The optimal Si-C-N ceramics (S2) show excellent EMW absorption performance over a wide temperature range. The Si-C-N ceramic had a promising applications at high temperatures.

Evaluation of seed-dispersal services by ants at a temperate pasture: Results of direct observations in an ant suppression experiment.

Ants disperse seeds of many plant species adapted to myrmecochory. While advantages of this ant-plant mutualism for myrmecochorous plants (myrmecochores) have been previously studied in temperate region mostly in forests, our study system was a pasture. Moreover, we used a unique combination of observing the effect of ant-activity suppression on ant dispersal and comparison of the contribution of ant and unassisted dispersal to the distance from mother plant. We established plots without and with ant-activity suppression (enclosures). We offered diaspores of a myrmecochorous (Knautia arvensis), and a non-myrmecochorous (Plantago lanceolata) species in a choice test and followed ants carrying diaspores during days and nights (focus of previous studies was on diurnal dispersal). We measured frequency and distances of ant dispersal and compared them with unassisted dispersal recorded using sticky trap method. The dispersal frequency was lower in enclosures (3.16 times). Ants strongly preferred diaspores of the myrmecochore to non-myrmecochore with 586 and 42 dispersal events, respectively (out of 6400 diaspores of each species offered). Ant dispersal resulted in more even and on average longer distances (maximum almost tenfold longer, 994 cm) in comparison to unassisted dispersal. Ant dispersal altered the distribution of distances of the myrmecochore from roughly symmetric for unassisted dispersal to positively skewed. Ants dispersed heavier diaspores farther. Ants dropped the majority of diaspores during the dispersal (which reduces clustering of seeds), while several (11%) were carried into anthills. Anthills are disturbed microsites presumably favorable for germination in competitive habitats. Ants provided non-negligible dispersal services to myrmecochorous K. arvensis but also, to a lesser extent, of non-myrmecochorous P. lanceolata.

Magnetic‐Driven Broadband Epsilon‐Near‐Zero Materials at Radio Frequency

AbstractEpsilon‐near‐zero (ENZ) materials, exhibiting unique physical characteristics such as near‐zero refraction, have aroused extensive interest and exhibit great potentials in novel applications of perfect absorbers, high‐harmonic generation, and nonlinear optical response. Here, for the first time, magnetic‐driven broadband ENZ materials are designed by fabricating polyvinyl alcohol (PVA)/Ni@carbon nanotubes (CNTs) films. Dielectric properties including real permittivity (ɛ′), imaginary permittivity (ɛ″), dielectric loss (tanδ), and impedance (Z) are investigated. When Ni@CNTs content reached 30 wt.%, negative permittivity transferred to positive permittivity at ≈11.5 MHz, and epsilon‐near‐zero (|ɛ′| &lt; 1) is realized from ≈9 to 14 MHz, exhibiting broad ENZ bandwidth of ≈5 MHz. Theory calculations confirm that delocalized electrons are introduced from CNTs, which improve the carrier mobility and achieve low frequency dispersion behavior. Longer interfacial polarization electric fields between PVA and CNTs are also demonstrated by theory calculations, enhancing the positive permittivity response to offset negative permittivity response from Ni@CNTs. These two mechanisms result in broadband ENZ at radio frequency. This film also exhibits excellent magnetic actuation ability under magnetic field, broadening applications from ENZ materials to novel fields such as magnetically actuated robots with perfect absorption, magnetic‐driven biomimetic aircrafts with shielding ability, magnetic‐driven photodetectors, etc.

Woodland loss differently affects seed dispersal by resident and migratory avian frugivores in olive grove-dominated landscapes

Seed dispersal by frugivores is a key ecological process underpinning the functionality of woodland patches and their capacity to maintain biodiversity in agricultural landscapes. Resident and migratory avian frugivores differ in temporal span of their local occurrence, as well as in mobility and territoriality. However, whether landscape homogenization by agriculture affects seed dispersal by avian frugivores differing in migratory strategy remains largely unexplored. We hypothesized a positive role of woodland patches on avian frugivore abundance and seed-dispersal frequency, and a differential impact of woodland loss and landscape simplification on resident and migratory frugivorous birds. We tested these hypotheses in 20 farms distributed along a gradient of woodland loss and olive cropland expansion in south Spain, considering woodland patches and olive fields as two habitats to survey avian frugivore abundance and frequency of seed dispersal. We confirmed that both the abundance and seed-dispersal frequency of avian frugivores were higher in woodland patches than in olive fields, and also that both decayed with decreasing woodland cover. This was largely mediated by a few European (winter) migrants and secondarily by some resident species. However, the woodland patches were unable to intercept sub-Saharan (summer) migrants in sufficient numbers as to make their contribution to dispersal of summer fruits meaningful. Woodland patches with higher seed-dispersal function were located predominantly in landscapes with high woodland cover and/or fruit availability. Moreover, a relatively high woodland cover in the landscape enhanced the seed dispersal function in woodland patches through a balance between high overall frugivore abundance and dispersal frequency, and some increased activity of resident and summer migrants. Our results also inform that the presence of particularly fruit-rich woodland patches can compensate the woodland cover required to maintain the function by enhancing the frequency of seed dispersal of all migratory groups. In contrast, to maintain the function of fruit-poor woodlands their cover at landscape scale should increase. Preserving and restoring woodland patches at landscape scale and enhancing their abundance and diversity of fruits could boost the activity of different disperser groups and their functional complementarity across agricultural landscapes.

Polarization controlled dispersion tunable optoelectronic oscillator and frequency octupling without bandpass filter

Polarization controlled dispersion tunable optoelectronic oscillator and frequency octupling without bandpass filter

Low-Cost L-Band to Ku-Band Frequency Reconfigurable BAR64-02V Controlled Antenna for Satellite, Military, and Radar Applications

A miniaturized edge-fed multi-band wideband (WB) sensor complementary split ring resonator (CSRR) and two folded pedal arms loaded antenna for wireless, ISM, military, Radar, and satellite applications is fabricated, tested, and investigated. The reduced ground plane at the bottom to makes the gain positive and leads to improvement in the radiation efficiency. Loading of antenna patch with two folded bicycle pedal-shaped arms results in an increased total electrical length and hence antenna could be tuned up to higher frequency bands. The appended two folded pedal arms enhance the value of gain and CSRR loading introduces additional resonant frequencies below −10dB reflection coefficient. The symmetrical ground width compression results in total antenna size miniaturization to 43.33% concerning the conventional circular microstrip antenna designed at a frequency of 2.45GHz. The antenna has a bidirectional radiation pattern with a gain of 5.21dBi and a radiation efficiency of 90.50%. The antenna exhibits four bands (2.13–2.58GHz), (2.77–3.89GHz), (5.65–6.56GHz), and (7.77–12.98GHz) within a frequency sweep of 1–15GHz, therefore it, is the most suitable element for Bluetooth, PCS, ISM band, 3G/4G/5G, Wi-MAX/WLAN/ Wi-Fi, and wireless, satellite, military, and RADAR applications. These bands are frequency reconfigured by two BAP64-02V PIN diodes in the pedal-arms fold locations with four switching combinations. The measured (frequency sweep: 1–23GHz) and simulated antenna reflection coefficient values are found in match except for a frequency range of 12–14 GHz. The antenna was fabricated on a low-cost FR-4 that holds well <12 GHz frequencies, and >12 GHz frequencies values this shows nonlinear and frequency dispersion.

Efficient microwave absorbing performance of Ni/carbon nanotubes assembled coronal hollow clusters

The development of wide-band microwave absorbing materials based on carbonaceous fillers remains a great challenge. In this study, carbon nanotubes (CNT) assembled coronal hollow clusters with efficient microwave absorbing performance have been obtained through successive hydrothermal and calcination process. Microstructural analysis reveals the distinct features of multiple assembly structures in the fabricated materials. The electromagnetic responses of Ni/CNT assembled clusters were examined across a frequency range of 2–18 GHz. Results demonstrate that the microwave frequency dispersion of electromagnetic parameters and reflection loss of Ni/CNT clusters are strongly influenced by weight loading. Multi-absorbing peaks with reflection loss better than − 40 dB could be achieved, while the equivalent absorbing band for RL< −10 dB covers 3.2–18 GHz, which account for 92.5% of the whole evaluated frequency range, and 62.5% for condition of RL< −20 dB. Furthermore, intrinsic attenuation beyond thickness derived semi-wavelength resonant absorption makes a major contribution to this superior performance. The underlying mechanism of dielectric response was investigated through Cole-Cole analysis and finite element simulation. ‘Micro-dipoles’ relaxation and hopping relaxation originated from defects within CNT and barrier between CNT, while the high magnetic dissipation capability of Ni nanoparticles make a major contribution to overall absorbing performance. All these are beneficial to regulation and optimization of microwave absorption performance of novel Ni/ CNT functionalized multistage architecture.

The Unified Quantum Picture of the World

This article describes a model of Unitary Quantum Field theory where the particle is represented as a wave packet. The frequency dispersion equation is chosen so that the packet periodically appears and disappears without form changings. The envelope of the process is identified with a conventional wave function. Equation of such a field is nonlinear and relativistically invariant. With proper adjustments, they are reduced to Dirac, Schrödinger and Hamilton-Jacobi equations. A number of new experimental effects have been predicted both for high and low energies. Fine structure constant (1/137) was determined in 1988, masses of numerous elementary particles starting from electron were evaluated in 2007 with accuracy less than 1 % . 2 pentaquarks, θ^+barion, Higgs boson and particle 28 GeV were discovered 11 years later, all of them were evaluated with high accuracy before. The overall picture of the world is based on a unify field. These Equations allow for the beginning of a universe without a Big Bang. Gravity ceases to be a mystery. In principle, a completely new type of "green" energy is possible for mankind.

Study on bandgap characteristics and vibration attenuation mechanism of double-oscillator power-exponent prism phononic crystal plate

This study introduces a local resonance mechanism to a periodic acoustic black hole (ABH) structure to achieve vibration control of plate structures and proposes a double-oscillator power-exponent prism phononic crystal. Results show that the periodic power-exponent prism can generate a high-frequency bandgap, the interior oscillator can generate a low-frequency bandgap, and the top oscillator can separate the frequency dispersion curve at around 700 Hz to form a bandgap with a width of 189 Hz. The double-oscillator power-exponent prism phononic crystal, composed of two types of oscillators and a power-exponent prism, can simultaneously have high-, middle-, and low-frequency bandgaps. Simulations and experiments show that it has a good attenuation effect on flexural vibration in the bandgap frequency band. The present results can provide a useful reference for bandgap design based on the combination of multiple mechanisms.