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In this paper, an intelligent prediction and design method of acoustic metamaterial beams based on deep learning is presented. A theoretical model of acoustic metamaterial beams is derived by using the spectral element method to calculate the band structure and transmission characteristic of beam-type acoustic metamaterial. A high-degree-of-freedom design space dataset of band structure and transmission characteristics is constructed. In addition, the vibration transmission characteristics of acoustic metamaterial beams are predicted and the on-demand inverse design of acoustic metamaterial beams is realized by constructing a fully connected deep learning neural network model. Furthermore, the forward prediction and reverse design network model is verified by using the autoencoder neural network model. Results show that the predicted value of the autoencoder neural network structure is in good agreement with the target value, which indicates the feasibility of the intelligent design method of acoustic metamaterials based on deep learning. The presented intelligent design method could be potentially utilized in the field of fast and efficient acoustic metamaterial design for low frequency vibration isolation in engineering structures. [ABSTRACT FROM AUTHOR]

We present the theoretical investigation on the flexural wave propagation and vibration attenuation characteristics in a Euler–Bernoulli beam-type metastructure with double-sides inertial amplified resonators. Based on Bloch theory, the dispersion relation and propagation characteristics of flexural waves are calculated by the spectral element method. The influences of system parameters on the flexural wave attenuation of the proposed beam-type metastructures are analyzed. Results show that broadband low-frequency flexural wave attenuation can be achieved by the proposed double-sides beam-type metastructures. The tunability of flexural wave band gap and vibration suppression performance significantly enhances. In addition, the low-frequency flexural wave band gap can be effectively modulated and optimized by changing the system parameters. [ABSTRACT FROM AUTHOR]

Sandwich structures are widely applied in modern industry such as aerospace, automobile as well as marine structures. However, the vibroacoustic properties of sandwich structures are adversely influenced by low effective mass. In this study, the flexural wave propagation characteristics and vibration mitigation performances of the periodic sandwich plate-type metastructures are investigated. The proposed sandwich plate-type metastructures are constituted of a sandwich plate with periodic thin-wall circular tube cores and periodically attached local stepped resonators. A finite element method combining Solid-Shell coupling numerical method and Bloch theory is presented to calculate the dispersion relations and the displacement fields of the eigenmodes of the infinite periodic sandwich plate-type metastructures. In addition, the acceleration frequency responses and vibration attenuation performances of finite periodic sandwich plate-type metastructures are numerically investigated and compared with the experimental measurements. Furthermore, the influences of geometric parameters on flexural wave band gaps are conducted. Results show that the sandwich plate-type metastructures can yield a low-frequency broad flexural wave band gap, in which the flexural wave propagation is conspicuously suppressed, resulting in significant flexural vibration attenuation. The flexural wave band gap and vibration attenuation performances can be effectively manipulated by designing geometric parameters of the sandwich plate-type metastructures. [ABSTRACT FROM AUTHOR]

Effective probing current-induced magnetization switching is highly required in the study of emerging spinâ€"orbit torque (SOT) effect. However, the measurement of in-plane magnetization switching typically relies on the giant/tunneling magnetoresistance measurement in a spin valve structure calling for complicated fabrication process, or the non-electric approach of Kerr imaging technique. Here, we present a reliable and convenient method to electrically probe the SOT-induced in-plane magnetization switching in a simple Hall bar device through analyzing the MR signal modified by a magnetic field. In this case, the symmetry of MR is broken, resulting in a resistance difference for opposite magnetization orientations. Moreover, the feasibility of our method is widely evidenced in heavy metal/ferromagnet (Pt/Ni20Fe80 and W/Co20Fe60B20) and the topological insulator/ferromagnet (Bi2Se3/Ni20Fe80). Our work simplifies the characterization process of the in-plane magnetization switching, which can promote the development of SOT-based devices. [ABSTRACT FROM AUTHOR]

We report on the development of a non-galvanic transition from a silicon micromachined to metallic rectangular waveguide for use in integrated waveguide systems at D-band (110–170 GHz). This transition overcomes the limitations of current solutions that require proper ohmic (galvanic) contact between both waveguides, and thus relaxes tolerance requirements in assembly and manufacturing. The transition uses an in-plane design which enables low-loss integration of micromachined waveguide components, as it eliminates the need for waveguide bends and complex multi-layer structures. We describe the RF design, analyze the EM simulation results, and explain the operating principle of the transition. To verify the concept, dedicated silicon micromachined and metallic waveguides are designed and fabricated. Characterization of the assembled samples shows good agreement with simulation. The transition achieves a typical insertion loss of 0.3 dB and return loss above 20 dB over most of the D-band. Measurement of multiple samples and repeated assemblies results in a variation of S21 of less than ±0.1 dB over the whole band, demonstrating good robustness and repeatability. By removing the need for galvanic connection, automated tools can then be used during system assembly, which enables industrial scale applications such as wireless communications. [ABSTRACT FROM AUTHOR]

This paper presents a novel micromachining process to fabricate a 140 GHz planar antenna based on gap waveguide technology to be used in the next-generation backhauling links. The 140 GHz planar array antenna consists of three layers, all of which have been fabricated using polymer-based microfabrication and injection molding. The 140 GHz antenna has the potential to be used as an element in a bigger 3D array in a line-of-sight (LOS) multiple input multiple output (MIMO) configuration to boost the network capacity. In this work, we focus on the fabrication of a single antenna array element based on gap waveguide technology. Depending on the complexity of each antenna layer's design, three different micromachining techniques, SU8 fabrication, polydimethylsiloxane (PDMS) molding, and injection molding of the polymer (OSTEMER), together with gold (Au) coating, have been utilized to fabricate a single 140 GHz planar array antenna. The input reflection coefficient was measured to be below − 11 dB over a 14% bandwidth from 132 to 152 GHz, and the antenna gain was measured to be 31 dBi at 140 GHz, both of which are in good agreement with the simulations. [ABSTRACT FROM AUTHOR]

Sandwich structures are widely used in the fields of aerospace, automobile as well as ship and offshore structures because of their excellent mechanical performances such as lightweight, high specific strength and high specific stiffness. In this study, the flexural wave band gaps and vibration isolation characteristics of sandwich plate-type elastic metamaterials are numerically and experimentally investigated. The proposed sandwich plate-type elastic metamaterials are constituted of local resonant stubs periodically deposited on a sandwich plate with periodic thin-wall aluminium tube cores. An efficient finite element method combined with a solid-shell coupling method and Bloch periodic boundary conditions is presented and validated by experimental measurements to calculate the dispersion relations and the acceleration frequency responses of sandwich plate-type elastic metamaterials. The influences of geometric parameters on the flexural wave band gaps are performed and discussed. Results show that the proposed sandwich plate-type elastic metamaterials can yield flexural wave band gaps in the low-frequency range and show significant performance on the flexural vibration isolation. Moreover, the flexural wave band gaps can be effectively modulated by the geometric parameters. [ABSTRACT FROM AUTHOR]

In this paper, a new structure of two-dimensional phononic crystals consisting of one or more rows of parallel rectangular rods placed periodically in a homogenous slab, in which the rods are not connected directly but linked through neck structures with the slab, is proposed, and the Lamb wave propagation in this structure is investigated with numerical analysis. The dispersion relations and the power transmission spectra are studied using the finite-element method. In contrast to the phononic crystals where the rods and the slab are completely in contact, the proposed structure with necks are proved to display band gaps at much lower frequencies. The displacement fields of the eigenmodes of the band edges are computed and analyzed to clarify the mechanism for the generation of the low-frequency band gaps. It is found that the low-frequency band gaps are attributed to the interaction between the local resonance of the rod inclusion connected with the neck and the Lamb modes of the four plates which are formed by the introduction of the neck. Furthermore, the influences of the geometry parameters of the neck on the band gaps are discussed. Numerical results show that band gaps are significantly dependent upon the width and the position of the necks while insensitive to the neck length. These properties of Lamb waves can potentially be applied to optimize band gaps, generate filters, and design acoustic devices. [ABSTRACT FROM AUTHOR]

In this paper, we present theoretical investigation on the wave propagation and acoustic bandgap characteristics in hybrid radial plate-type elastic metamaterials constituted of periodic double-sides composite stubs deposited on one-dimensional binary radial phononic crystal plate. The dispersion relations and the displacement fields of the eigenmodes are calculated by using the finite element method on the basis of two-dimensional axial symmetry models. Numerical results show that the proposed hybrid radial plate-type elastic metamaterial can generate lowering and widening acoustic bandgaps and yield a significant expansion of the relative bandwidth by a factor of 5 compared to the traditional radial plate-type elastic metamaterial with double-sided composite stubs. The displacement fields of the eigenmodes are applied to reveal the formation mechanism of lowering and widening acoustic bandgaps. In addition, the influences of the physical and geometrical parameters on the bandgaps are further performed. These low-frequency broadband acoustic bandgap properties in the radial plate-type elastic metamaterials can probably be applied to vibration and noise reduction in the rotary machines and structures. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the nonlinear dynamic characteristics of a gear pair system with dynamic backlash subjected to internal and external periodic excitations. The dynamic model of a viscously damped single degree of freedom gear pair model with periodic time-varying stiffness, dynamic backlash, static transmission error and external periodic excitation is established. The incremental harmonic balance method (IHBM) is applied to analyze the frequency response characteristics as well as the effects of dynamic backlash, time-varying stiffness, excitation force amplitude and damping ratio on the dynamic characteristics of the gear pair system. The analysis results are compared with the numerical integration results to show accuracy and authority of the IHBM. The difference between the constant backlash and the dynamic backlash models is also discussed. The results show that the nonlinear dynamic characteristics such as parametric resonance, multi-valued properties and jump phenomena are strongly attributed to the interaction between time-varying stiffness and backlash. Significantly, under combined internal and external periodic excitations, the multi-valued properties and jump phenomena occur not only in primary resonance frequency but also in super harmonic frequency. The increase of the dynamic backlash and damping ratio could effectively control the nonlinear vibration of gear system; whereas the excitation force amplitude has less influence on the nonlinear dynamic characteristics and the increase of the excitation force amplitude could no longer control the nonlinear vibration of gear system, which is different from the dynamic characteristics under internal periodic excitations. [ABSTRACT FROM AUTHOR]

Integration of a 140-GHz packaged low-temperature cofired ceramic (LTCC) antenna with a power detector is demonstrated under the concept of antenna-in-package. The detector is designed on an indium phosphide (InP) process. A grid array antenna in LTCC is designed to provide package for the detector. Coplanar ground–signal–ground (GSG) bond wires are used to connect the detector and the antenna. Parallel plate mode is observed in the InP substrate and absorbed by the LTCC substrate. The comparison between the measured responsivity of the power detector with and without the antenna indicates the acceptable insertion loss of the coplanar GSG bond wires transition. It shows a feasible solution for the D-band front-end integration and packaging. [ABSTRACT FROM PUBLISHER]

This paper presents an implementation solution for a digital baseband receiver, which consists mainly of an analog symbol timing recovery (STR) block and a digital carrier recovery block. The STR is realized based on “one-sample-per-symbol” sampling, resulting in relaxed requirement on the A/D converter’s sampling speed. In this sense, the proposed implementation solution is hardware efficient. To functionally verify the solution, a proof-of-concept E-band link system is implemented and tested in the laboratory, which supports 5-Gbit/s data traffic using 16 quadrature amplitude modulation. The test results demonstrate that the proposed solution works for high-capacity millimeter-wave radios for point-to-point links, one of the targeted applications. [ABSTRACT FROM AUTHOR]

In this paper, we theoretically investigate the band structures of Lamb wave in one-dimensional radial phononic crystal (PC) slabs composed of a series of alternating strips of epoxy and aluminum. The dispersion relations, the power transmission spectra and the displacement fields of the eigenmodes are calculated by using the finite element method based on two-dimensional axial symmetry models in cylindrical coordinates. The axial symmetry model is validated by three-dimensional finite element model in Cartesian coordinates. Numerical results show that the proposed radial PC slabs can yield several complete band gaps with a variable bandwidth exist for elastic waves. Furthermore, the effects of the filling fraction and the slab thickness on the band gaps are further explored numerically. It is worth observing that, with the increase of the filling fraction, both the lower and upper edges of the band gaps are simultaneously shifted to higher frequency, which results from the enhancement interaction between the rigid resonance of the scatterer and the matrix. The slab thickness is the key parameter for the existence and the width of complete band gaps in the radial PC slabs. These properties of Lamb waves in the radial PC plates can potentially be applied to optimize band gaps, generate filters and design acoustic devices in the rotary machines and structures. [ABSTRACT FROM AUTHOR]

Impact noise characterized by high peak value and short duration is very common source of noise in the industries and in many cases can be summed up in the noise radiated by collision of two cylinders. In order to precisely predict the impact noise radiated by collision of two cylinders, a modified theoretical prediction model was established based on the Palmgren's cylinder contact empirical model and acoustics theory. Then a numerical simulation method combining the finite element method (FEM) and the transient boundary element method (TBEM) had been presented to verify the modified theoretical model and further discuss the mechanism of impact noise. Both the contact force and impact noise of collision cylinders by the modified theoretical model were compared with the numerical results as well as the prediction results by the original theoretical model. It indicated that the results by modified theoretical prediction model are in good agreement with the numerical results, indicating better prediction superior to the original model. The impact noise radiated by collision cylinders is attributed to the rigid body acceleration. Furthermore, the experimental validations were conducted to verify the modified theoretical prediction model and numerical simulation results. [ABSTRACT FROM AUTHOR]

The temperature and humidity of the shelterbelt micro-climate on both horizontal and vertical scales in the extremely drought area were measured with multiple HOBO temperature and humidity automatic observation equipments in the hinterland of the Taklimakan Desert. The results show that the shelterbelt ecosystem of the desert highway plays typical micro-climate adjustment rolesin stabilizing surface air temperature and increasing air humidity, and so on. Solar radiation significantly affects both temperature and humidity of surface layers, and it has a positive correlation with the temperature but a negative correlation with the air humidity. When it is cloudy, the weather has a great impact on keeping temperature and humidity in the shelterbelt. The shelterbelt also significantly influences the environment, and the micro-climate in the belt has an obvious characteristic of cooling and humidification: compared with the original sand area, the temperature in the shelterbelt is always lower and the humidity is always higher. Moreover, the temperature range at the shelterbelt edge is greater than that in the sand area, but the humidity is always higher. Our conclusion is that the vertical-effect range of temperature of the shelterbelts is 4 -10 m, and the humidity range is 6 to 8 m; the horizontal-effect range of temperature is 16 m and the humidity range is about 24 m. [ABSTRACT FROM AUTHOR]

A proof of concept on-/off- keying (OOK) modulator is designed and implemented in a commercial heterojunction bipolar transistors IC process. The modulator circuit consists of an amplifier/latch structure, which is used as an OOK modulator for the first time. One of its advantages is that the topology may be implemented in both field effect transistor and bipolar technology. The measurement results correspond well with simulation and show that the modulator is capable of handling carrier frequencies up to 28 GHz, and data rates up to 14 Gbps. The isolation of the modulator in the off-state is better than 27 dB over the whole frequency range. [ABSTRACT FROM PUBLISHER]