Amplitude Transmission Coefficients Research Articles

Результати експериментальних досліджень акустичних характеристик звукопоглинаючих конструкцій для ТРДД

The subject of the research in this article is an acoustic liner designed to reduce aircraft noise in a wide frequency range. The purpose of the study is to determine the acoustic characteristics of an acoustic liner. Tasks: development of a theoretical model of the acoustic liner in the form of tubes of different lengths, calculation of the natural frequencies of each tube of the developed liner, determination of the frequency range in which sound absorption will occur, production of a test sample, and experimental determination of the sound absorption coefficient. An experimental setup is used to determine the sound absorption coefficient of the developed liner, which determines the acoustic characteristics of the acoustic liners using the standing wave method. This study presents the results of: calculation of the natural frequencies of the proposed liner, calculation of the dependence between the amplitude transmission coefficient and the frequency of the exciting force, and measurement of the acoustic characteristics of the proposed acoustic liner. The scientific and practical novelty of the obtained results is as follows: to solve the problem of noise absorption in a wide frequency range, a theoretical model of the acoustic liner, which should consist of tubes of different lengths, was developed. Each tube has its own frequency of oscillation of the air inside the tube. As the path of sound travel inside the tube increases, the natural frequency of the tube decreases. When tubes of different lengths are placed on the test sample, it is possible to obtain an acoustic liner with a significant number of natural frequencies, that is, noise will be absorbed in a wide frequency range. According to the calculation results, the proposed acoustic liner, consisting of seven types of tubes of different lengths, has more than 20 natural frequencies in the frequency range from 500 Hz to 4500 Hz, that is, the frequency range of absorption is quite wide. In order to verify the theoretical calculations with the help of a 3D printer, experimental samples of the proposed acoustic liner, as well as a real acoustic liner used to reduce the noise of the D-18T engine, were made and their experimental studies were carried out. The research results show that the proposed acoustic liner reduces noise in a wide frequency range. In the frequency range from 1300 Hz to 3500 Hz, the sound absorption coefficient exceeds 0.4, and in the range from 1500 Hz to 2600 Hz, the sound absorption coefficient is above 0.5. In the specified frequency ranges, the proposed acoustic liner has significant advantages over the D-18T acoustic liner. By reducing the cross-section of the tubes, or increasing the number of tubes of the experimental sample, it is possible to significantly increase the frequency range of sound absorption.

Nonlinear laser absorption on metal surface embedded with nanoparticles in the presence of external magnetic field

A nonlinear analytical model is developed for the absorption of a p-polarized laser that is obliquely incident on a metal surface embedded with metallic nanoparticles under the influence of an external magnetic field. The model suggests that the absorption coefficient is proportional to the angle of incidence and cube of nanoparticle-radius, but inversely proportional to the square of interparticle separation. Obtained results show that the laser absorption by the nanoparticles is substantially amplified due to plasmon resonance in the presence of an external magnetic field. The absorption coefficient has a sharp peak at surface plasma resonance where is the plasma frequency and it shows explicit dependence on the amplitude transmission coefficient of the incident wave. Absorption coefficient is obtained for gold nanoparticles for different incident angles, radii and interparticle separations and this study is of direct relevance in high performance optoelectronic devices, solar cells and nanomedicines.

Effect of unloading behavior on stress wave transmission in a double-scale discontinuous rock mass

Stress wave propagation through double-scale discontinuous rock masses considering unloading behavior was investigated. The piecewise linear loading and unloading models of macrojoint were proposed, which were combined with a split three-characteristics mothed to investigate the stress wave transmission properties. The effects of the waveform, frequency, amplitude and propagation distance on the energy and amplitude transmission coefficients were discussed. The results of the present study were compared with the traditional study that considered single-scale discontinuities. The results show that the present study can effectively analyze the effect of the waveform, frequency, amplitude and propagation distance on the energy and amplitude transmission coefficients. The energy and amplitude transmission coefficients for rectangular wave are the largest, while those for triangular wave are the smallest. The energy and amplitude transmission coefficients decrease as frequency and propagation distance increase. The energy and amplitude transmission coefficients increase as the amplitude increase. The results also show that the effect of macrojoint unloading effect and microdefect on wave transmission can be considered comprehensively in the present study. The unloading effect of macrojoint causes the smaller energy transmission coefficient, while it does not affect the amplitude transmission coefficient. The microdefects cause smaller energy and amplitude transmission coefficients. Highlights The effect of unloading behavior on wave propagation in rock mass was studied. The piecewise linear loading and unloading models of macrojoint were proposed. Macrojoint and microdefect in rock mass were considered in a framework. Energy and amplitude transmission coefficients were studied in present study.

Анализ методов измерения диэлектрических свойств материалов в СВЧ диапазоне длин волн.

One of the modern trends in the development of communication systems, information and telecommunication systems, air traffic control systems, etc. is the transition and development of higher-frequency wavelength ranges. In this regard more and more stringent requirements (in terms of spectrum, out-of-band and spurious radio emission, and in the shape of the output signal) are imposed on radio engineering devices that transmit and receive microwave radio signals. As a result, the requirements for the design and functional features of microwave electronic devices are increasing. One of these requirements is to assess the degree of compliance with the required values of dielectric properties of materials used in the design of microwave electronic devices. This requirement is justified by the fact that the electrical parameters of such microwave devices as: strip filters, power dividers, printed antennas and others, directly depend on the dielectric properties of the materials used in their substrate designs. In this regard, three main methods have now emerged for assessing the dielectric properties of materials: the resonant method, the non-resonant method, and the free space method. Aim. The aim of this article is to carry out a comparative analysis of the known methods for measuring the dielectric properties of materials in the microwave range of wavelengths and devices for their implementation. Materials and methods. The authors of the article reviewed the scientific literature of domestic and foreign publications. Results. For each of the methods for measuring the dielectric properties of materials, their main idea, practical implementation, a mathematical model for processing experimental data and areas of application are given. The advantages and disadvantages for each of the methods for measuring the dielectric properties of materials are given too. Conclusion. The applicability of each of the considered methods depends on such factors as: the shape of the investigated dielectric material, its state of aggregation, the possibility of measuring amplitude or complex transmission and reflection coefficients, the presence of an anechoic chamber, etc.

Dissipative optomechanical coupling with a membrane outside of an optical cavity

We theoretically study an optomechanical system, which consists of a two-sided cavity and a mechanical membrane that is placed outside of it. The membrane is positioned close to one of its mirrors, and the cavity is coupled to the external light field through the other mirror. Our study is focused on the regime where the dispersive optomechanical coupling in the system vanishes. Such a regime is found to be possible if the membrane is less reflecting than the adjacent mirror, yielding a potentially very strong dissipative optomechanical coupling. Specifically, if the absolute values of amplitude transmission coefficients of the membrane and the mirror, $t$ and $t_m$ respectively, obey the condition $ t_m^2< t\ll t_m\ll 1$, the dissipative coupling constant of the setup exceeds the dispersive coupling constant for an optomechanical cavity of the same length. The dissipative coupling constant and the corresponding optomechanical cooperativity of the proposed system are also compared with those of the Michelson-Sagnac interferometer and the so-called "membrane-at-the-edge" system, which are known for a strong optomechanical dissipative interaction. It is shown that under the above condition, the system proposed here is advantageous in both aspects. It also enables an efficient realization of the two-port configuration, which was recently proposed as a promising optomechanical system, providing, among other benefits, a possibility of quantum limited optomechanical measurements in a system, which does not suffer from any optomechanical instability.

Features of transmission of electromagnetic waves through composite nanoresonators including epsilon-near-zero metamaterials

Transmission of electromagnetic waves through nanometric multilayers (nanoresonators) including a main composite layer made of two alternating strips of low-absorbing dielectrics that is sandwiched between epsilon-near-zero (ENZ) or metallic spacer layers has been modeled. Analytical models are based on exact solutions of electromagnetic boundary problems. The spacers with the definite properties lead to extreme dependences of amplitude transmission coefficients on the system parameters and drastic increase in phase difference of the transmitted waves. These effects are most pronounced for subwavelength multilayer thicknesses due to multibeam interference features in the nanoresonator, and they can be amplified when the main layer and (or) the whole system thicknesses decrease. The investigated transmission features take place under variations of the system parameters such as anisotropy of the main layer materials, non-ideal realization of ENZ materials, oblique incidence of the exciting radiation (for small incidence angles). The obtained results can have applications in development of ultra-thin nanophotonics devices using phase transformation of transmitted waves.

Generalized statistical dynamical theory of x-ray diffraction by imperfect multilayer crystal structures with defects

The generalized statistical dynamical theory of x-ray scattering by imperfect single crystals with randomly distributed Coulomb-type defects has been extended to characterize structure imperfections in the real multilayers of arbitrary thickness in Bragg diffraction geometry. The recurrence relations for the coherent amplitude reflection and transmission coefficients of such multilayers, which consist of any number of layers with constant strain and randomly distributed defects in each one, have been derived within the concept of the dynamical wave field, i.e., the so-called Ewald-Bethe-Laue approach, with rigorous accounting for boundary conditions at layer interfaces. The analytical expression for the differential dynamical diffuse component of the reflection coefficient of an imperfect multilayer system has been obtained as well. This expression establishes direct connection between the distribution of the diffuse scattering intensity in a momentum space and statistical characteristics of defects in each layer. In addition, the integrals from differential diffuse scattering intensity over the Ewald sphere and over vertical divergence have been found, which correspond to diffuse components in measurements of rocking curves and reciprocal space maps, respectively. The developed theory provides the dynamical description for the one- and two-dimensional angular distributions of the mutually consistent coherent and diffuse components of x-ray scattering intensities, which are measured by the high-resolution double- and triple-crystal diffractometers, respectively, from imperfect films, multilayer structures, superlattices, etc. Examples of simulated rocking curves for the imperfect superlattice with defects of several types and reciprocal space map for the ion-implanted sample of yttrium iron garnet film with defects are given and discussed.

Effect of interfacial adhesion on the ultrasonic interaction with adhesive joints: A theoretical study using spring-type interfaces.

The effect of interfacial properties on the reflection and transmission characteristics of ultrasonic waves at adhesively bonded joints is theoretically investigated. An adhesive joint is modeled as a double-interface model, namely, a homogeneous layer coupled to adherends by two spring-type interfaces with different interfacial stiffnesses. For the normal incidence of a one-dimensional longitudinal wave, theoretical results are obtained and validated by finite element simulation. When the thickness of the adhesive layer is sufficiently small compared to the wavelength, the amplitude reflection and transmission coefficients show monotonic dependence on frequency, which can be explained by the theoretical relation of the double-interface model to a single spring-type interface model. The reflection and transmission behavior is invariant if the values of the two interfacial stiffnesses are interchanged. For a relatively thick adhesive layer, on the other hand, the reflection coefficient shows local minima at multiple frequencies. As one interfacial stiffness decreases, the local minimum frequencies decrease and the local minima increase. If the values of the two interfacial stiffnesses are interchanged, the reflection coefficient remains invariant but the reflection waveform shows different features. The obtained reflection and transmission characteristics are discussed in light of the characterization of the interfacial adhesion.

A novel pressure sensor based on series-coupled double microring resonators with a simple beam

ABSTRACTWe propose and analyse a novel optical pressure sensor based on series-coupled double microring resonators (SDMRRs) on a simple beam. The pressure applied on the sensor is measured through the change of the optical transmission spectrum at the output port. The optical transmission performances of the SDMRRs have been analysed and compared with the single and paralleled-coupled structures by the method of finite element analysis and numerical simulation. The simulation results showed that the stress sensitivity is 0.0225 kPa–1 and linear measurement range of the sensor is 30 kPa. Furthermore, the influence of the amplitude transmission coefficient, half round phase shift and microring radius on the sensitivity have been investigated to optimize the sensor performance. This proposed sensor can be used for the smaller pressure detection in automotive, aerospace, oil/logging equipment and other harsh environmental application.

Theoretical Investigation on Coupled Plasmon Waveguide Resonance in Real and Complex Domain for High Precision Nanoplasmonic Sensing

Numerical investigations on modified multilayer coupled plasmonic structure, termed as coupled plasmon waveguide resonance (CPWR) structure, have been presented in real as well as complex plane domain. Coupling of waveguide resonance and plasmonic resonance results in dual resonance. Reflectance, field enhancement, and phase-dependent resonant behavior have been analyzed in angular interrogation for three different metal layers in order to optimize the structure with proper choice of metal layers. The resonance parameters have also been theoretically investigated in differential angular regime for better comparison of the shape of different resonance curves. Complex amplitude reflection and transmission co-efficients are analyzed with circular graphical plots in the complex plane. Simultaneous observations of the real and imaginary parts as well as amplitude and phase of the reflection and transmission co-efficients have been demonstrated. Different conventional optical polymers have been considered as waveguide layer materials and their respective real and complex plane analyses demonstrate the comparison for the proper choice of the waveguide layer. Moreover, the resonance parameters and the differential plots in real as well as complex plane for coarse and precise measurement have also been investigated for nanoplasmonic sensing applications to provide improved resolution.

Enhanced magnetochiral effects at microwave frequencies by a single metamolecule

We have experimentally and numerically studied the directional birefringence of $X$-band microwaves by magnetochiral (MCh) effects of a single metamolecule under dc magnetic fields at room temperature. Phase and amplitude transmission coefficients from top and bottom, i.e., $S$ parameters of ${S}_{21}$ and ${S}_{12}$, are measured for the single metamolecule consisting of a copper chiral structure and ferrite cylinder in a waveguide. By applying a dc magnetic field, we observe a difference between ${S}_{21}$ and ${S}_{12}$, which is an emergence of the MCh effects with simultaneous space-inversion and time-reversal symmetry breaking. Numerical calculation based on a finite element method reproduces well the experimental results of the MCh effects. The MCh effect can be enhanced by using the magnetic resonance of the ferrite cylinder. Notably, numerical calculation predicts that the MCh effect is extremely enhanced by interacting magnetic resonance with a specific resonant structural optical activity, leading to a giant MCh effect. The giant MCh effect observed in the present study originates from the one-way transparency caused by the Fano resonance in the metamolecule.

To the analyticity of the effective refractive index

The possibility to describe the plane-wave propagation in a periodic layered medium in terms of effective parameters is considered. It is shown that, for a finite system, the effective refractive index can be determined with the help of the amplitude transmission coefficient. The analyticity of the effective refractive index as a function of frequency is studied. It is shown that the effective refractive index is an analytic function of frequency, and the Kramers–Kronig relations, which connect the real and imaginary parts, are found.

Beam control algorithm for an active phased array antenna with dome lens

An algorithm for control of the phases of an active phased array antenna (APAA) with dome lens that takes into account distorting influence of the lens and combines tabular and computational methods for control of the antenna element phases is proposed. An algorithm for control of the amplitude transmission coefficients of receiving channels of the APAA modules for formation of a difference pattern with deep direction- finding null is also proposed.

Transmission of ultrasonic waves at oblique incidence to composite laminates with spring-type interlayer interfaces.

The transmission characteristics of ultrasonic waves at oblique incidence to composite laminates are analyzed theoretically by the stiffness matrix method. The analysis takes into account the presence of thin resin-rich regions between adjacent plies as spring-type interfaces with normal and shear stiffnesses. The amplitude transmission coefficient of longitudinal wave through a unidirectional laminate immersed in water is shown to be significantly influenced by the frequency, the interlayer interfacial stiffnesses, and the incident angle. Using Floquet's theorem, the dispersion relation of the infinitely extended laminate structure is calculated and compared to the transmission coefficient of laminates of finite thickness. This reveals that the ranges of frequency and interfacial stiffnesses where the Floquet waves lie in the band-gaps agree well with those where the transmission coefficient of the finite layered structure is relatively small, indicating that the band-gaps appear even in the laminate with a finite number of plies. The amplitude transmission coefficient for an 11-ply carbon-epoxy unidirectional composite laminate is experimentally obtained for various frequencies and incident angles. The low-transmission zones observed in the experimental results, which are due to the critical angle of the quasi-longitudinal wave and the Bragg reflection, are shown to be favorably compared with the theory.

OS1525-422 CFRP積層板の層間特性評価に向けた斜角入射超音波伝搬挙動の理論的検討

The ultrasonic wave transmission behavior through a unidirectional CFRP laminate with spring-type interlayer interfaces immersed in water is investigated using the stiffness-matrix approach. The amplitude transmission coefficient is shown to be influenced by the frequency, angle of incidence, and interlayer interfacial stiffnesses. Using Floquet's theorem, the band structure of Floquet wave propagating in the infinitely laminated structure is computed and compared to the transmission coefficient of the immersed laminate with finite number of plies. This reveals that the band-gaps of Floquet waves are in good agreement with the region where the transmission coefficient falls to a low level, indicating that the band-gaps do appear even in the laminate of finite thickness.

OS0411-386 平板接触部におけるラム波高調波発生に関する数値解析

In this study, the nonlinear behavior of Lamb waves at contacting edges of linear elastic plates is investigated by the perturbation analysis using the hybrid finite element method. The contacting surfaces are modeled as a nonlinear spring interface, which takes into account quadratic nonlinearity. For the incidence of the lowest-order symmetric (SO) Lamb mode, the amplitude reflection and transmission coefficients of the SO mode, which are obtained by linear analysis, vary monotonically with the incident frequency. Due to the nonlinear interaction of the incident SO mode with the contacting interface, the double-frequency SO mode is generated. The amplitude of the generated second-harmonic SO mode has a sharp peak at the half of the resonance frequency of the contacting interface.

Effects of Interlayer Interfacial Stiffness on Ultrasonic Wave Propagation in Composite Laminates at Oblique Incidence

The transmission characteristics of ultrasonic wave impinging obliquely on composite laminates are analyzed. Incorporating the influence of thin resin-rich regions between adjacent plies by spring-type interfaces, the amplitude transmission coefficient of a unidirectional composite laminate immersed in water is calculated by the stiffness-matrix method. Using Floquet's theorem, the dispersion relation for the infinitely laminated structure is also calculated. Comparison between two results reveals that the frequency band-gaps in the dispersion relation agree well with the low-transmission frequency ranges of the finite laminated case. Comparing with the experimental transmission coefficients for an 11-ply carbon-epoxy composite laminate, the theoretical results are verified.

Object image correction using an X-ray dynamical diffraction Fraunhofer hologram

Taking into account background correction and using Fourier analysis, a numerical method of an object image correction using an X-ray dynamical diffraction Fraunhofer hologram is presented. An example of the image correction of a cylindrical beryllium wire is considered. A background correction of second-order iteration leads to an almost precise reconstruction of the real part of the amplitude transmission coefficient and improves the imaginary part compared with that without a background correction. Using Fourier analysis of the reconstructed transmission coefficient, non-physical oscillations can be avoided. This method can be applied for the determination of the complex amplitude transmission coefficient of amplitude as well as phase objects, and can be used in X-ray microscopy.

Two-photon quantum interference in plasmonics: theory and applications

We report perfect two-photon quantum interference with near-unity visibility in a resonant tunneling plasmonic structure in folded Kretschmann geometry. This is despite absorption-induced loss of unitarity in plasmonic systems. The effect is traced to perfect destructive interference between the squares of amplitude reflection and transmission coefficients. We further highlight yet another remarkable potential of coincidence measurements as a probe with better resolution as compared to standard spectroscopic techniques. The finer features show up in both angle resolved and frequency resolved studies.

Study of reflection and transmission of plane waves at thermoelastic-diffusive solid/liquid interface

The paper concentrates on the study of reflection and transmission characteristics of waves at the interface of a thermoelastic-diffusive solid half-space underlying an inviscid liquid. The analytic expressions for amplitude ratios, reflection and transmission coefficients, in terms of incident angles and material parameters have been obtained for quasi-longitudinal (qP) and quasi-transverse (qSV) wave incidence. The normal and grazing incidence cases have also been derived and discussed. The total reflection phenomenon has also been discussed. The energy law has been shown to be obeyed by the incidence, reflected and transmitted waves by deriving energy equation and its simulation. The numerical computations of reflection and transmission coefficients have been carried out for copper material half-space in contact with water at the interface by using MATLAB software. The computer simulated results have been presented graphically in order to bring out clear comparison of various situations.