Design Of Absorber Research Articles

Crashworthiness of Additively Manufactured Auxetic Lattices: Repeated Impacts and Penetration Resistance.

Auxetic materials have recently attracted interest in the field of crashworthiness thanks to their peculiar negative Poisson ratio, leading to densification under compression and potentially being the basis of superior behavior upon impact with respect to conventional cellular cores or standard solutions. However, the empirical demonstration of the applicability of auxeticity under impact is limited for most known geometries. As such, the present work strives to advance the investigation of the impact behavior of auxetic meta-materials: first by selecting and testing representative specimens, then by proceeding with an experimental and numerical study of repeated impact behavior and penetration resistance, and finally by proposing a new design of a metallic auxetic absorber optimized for additive manufacturing and targeted at high-performance crash applications.

Conformal and transparent broadband absorber comprising patterned resistivity film

Broadband absorber can achieve zero transmission, small reflection and high absorption in a certain frequency band. However, the design of high-performance broadband absorbers remains a challenge. Taking advantage of the broadband superposition property of a simple structure, we propose a conformal and transparent broadband microwave absorber, which consists of multi-layer polyethylene terephthalate (PET) dielectric layers, indium tin oxide (ITO) patches and loops. The absorber has an absorptivity of over 90 % in the range of 12.78–69.16 GHz, along with polarization stability and ±50° angle of incidence insensitivity. Experimental results indicate that the numerical simulation and actual performance show good agreement. In addition, the properties of flexibility and optical transparency are expected to be applied in scenarios such as curved surfaces and portholes.

Identification of Control Parameters Using Taguchi Method for Hybrid Real-Binary Differential Evolution Algorithm and Its Applications in Electromagnetic Optimization

The hybrid real-binary differential evolution (HDE) algorithm has been proficient in addressing electromagnetic optimization problems (EOPs) involving both real and binary variables. However, its optimization performance on different control parameter (CP) settings is not further studied, and the method to determine the values of CPs is more likely to use the trial-and-error method, which lacks universality on both unimodal and multimodal benchmarks. To completely account for the effect of CPs in HDE, the Taguchi method is utilized to identify the values of each CP. The orthogonal experiment result is the average rank of the mean values of 23 benchmark functions obtained by HDE and other classic optimization algorithms. Based on the analysis of variance results, three CPs that have a major effect on the performance of HDE are selected, and each of them is changed from level 1 to level 5 to further obtain the best combination of CPs, which is indicated as HDEN1. To further enhance the local search ability of HDEN1 for the global best, a modified algorithm (HDEN2) is proposed based on a novel mutation strategy selection method, and the simulation results demonstrate that the minimum values obtained by HDEN2 are smaller than those obtained by HDEN1. Two EOPs, including planar microwave absorber and Yagi-Uda antenna designs, are solved to validate the performance of HDEN1 and HDEN2. The results reveal that the HDEN1 and HDEN2 outperform HDE, demonstrating the efficacy of the proposed method for identifying the CPs of HDE. In the end, a low profile and wideband RCS reduction pixelated checkboard metasurface is optimized utilizing the HDEN2, proving that the proposed algorithm can be a good candidate for hybrid real-binary electromagnetic problems.

Design and Fabrication of Flexible Woodpile Structured Nanocomposite for Microwave Absorption Using Material Extrusion Additive Technique

The explosive growth of electronics and the widespread use of transient power sources have given rise to an undesirable and uncontrolled consequence of electromagnetic interference (EMI). It is crucial to address and mitigate the issues caused by EMI by developing effective shielding techniques. The material extrusion additive technique provides a solution through its versatile 3D printing of polymeric ink, offering advantages such as design flexibility, structural complexity, and environmental sustainability. The primary objective of this study is to investigate the rheological properties, electromagnetic properties, and thermal stability of nanocomposites consisting of Polydimethylsiloxane (PDMS) and Multi-Walled Carbon Nanotubes (CNTs). The aim is to utilize these findings for the design and 3D printing of a microwave absorber with high efficiency. Composite inks containing 50 vol% (C50) and 60 vol% (C60) of CNTs exhibit favorable shear-thinning behavior and shape retention. On the other hand, lower CNT percentages result in inconsistent viscosity, rendering the inks non-printable. Thermogravimetry analysis reveals that an increase in CNT vol% leads to a decrease in the thermal stability of 3D-printed PDMS-CNT nanocomposites. Higher CNT proportion enhances electric polarization, and attenuation capacity, as evidenced by measurements of complex permittivity and dielectric loss tangent. X-Ray Diffraction analysis was employed to examine the effect of CNT inclusion in the composites. A woodpile-structured metamaterial microwave absorber based on gradient index (GWMMA) was designed by manipulating geometric parameters and CNT vol%. Fifteen unit cell configurations were generated and subsequently chosen based on their exceptional attenuation capabilities, low impedance, and narrower filament width for simulations. The GWMMA demonstrates exceptional absorption performance, surpassing reflection loss values of −10dB. Incorporating a third filament stacking into the woodpile structure augments its efficacy, yet further additions of stackings result in diminishing returns. Experimental validation of a selected 3D-printed GWMMA structure of C60 with a width of 0.75 mm confirms its absorption capabilities, closely aligning with the simulated results. The GWMMA exhibits promising performance for microwave absorption, with absorption values exceeding 90%. Simulations indicate the adjustability of the GWMMA's bandwidth and absorption capabilities through alterations in array periodicity and cell size. Its spatial scale aligns with sub-wavelength structures, establishing it as a representative Metamaterial Absorber (MMA).

High performance selective light absorber based on nickel nanopillar array for photothermal conversion

Efficient absorption of solar radiation holds the key to photothermal utilization; however, realizing solar absorber designs with high absorption efficiency remains challenging. Herein, a nickel-based metamaterial selective solar absorber with a nanopillar array structure was proposed to realize nearly perfect optical absorption over a broad spectrum. The average absorbance is up to 96% in the 300–2033 nm wavelength range. Notably, a reasonably detailed analysis of the physical mechanism of the proposed absorber was performed in this paper, attributing the exceptional broadband absorption to the concurrent interaction with surface plasmon resonance, quarter-wavelength resonance, and electric dipole resonance. The absorption efficiency declines significantly when λ > 2.5 μm, with only 20% absorptivity at λ = 6 μm in the radiation-absorbing transition region. This decline is desirable, as it contributes to reducing the emissivity in the mid-infrared range and, therefore, prevents self-radiation. The results demonstrate that the selective absorber possesses the potential to capture solar energy within a broadband, while avoiding undesirable self-radiation, thereby enhancing the integral efficiency of the solar energy conversion system. Moreover, the absorption spectrum shows insensitivity to polarization and angle of incidence. The selective solar absorber proposed here offers excellent performance with a simple structure, showing great promise in the field of photothermal conversion.

The use of a piece sound absorber to reduce the impact of noise on workers in the dairy industry on the example of industrial enterprises of the Republic of Mordovia

The paper analyzes the working conditions of workers in the dairy industry, which showed that the prevailing harmful production factor is the increased noise level. It has been proven that noise has a negative impact not only on the hearing organs, but also on the whole organism as a whole as a general biological irritant, therefore, reducing noise expansion due to engineering solutions is an urgent task of our time. The article assesses the noise impact on operators of the dairy industry as part of a special assessment of working conditions. The analysis showed that the excess noise level is observed at all workplaces. To protect workers from an increased noise level, a design of a sound-suppressing piece sound absorber is proposed, which is distinguished by high sanitary and hygienic properties. The use of sound-suppressing piece sound absorbers will improve working conditions from a harmful class to an acceptable one.

3D-printed stepped structure based on graphene-FeSiAl composites for broadband and wide-angle electromagnetic wave absorption

The design and preparation of absorbers with ultra-wide bandwidth and wide-angle absorption characteristics are crucial technologies for addressing electromagnetic (EM) pollution. In this paper, a stepped structure absorber was fabricated of graphene (GR)-FeSiAl/polylactic acid (PLA) composite by 3D printing technology. The absorber contains four layers, the bottom layer being a slab with periodic square holes, and the upper layer is a periodic distribution of three cubes with equal thickness and gradient changes in side length. It is shown that the stepped structure achieves a minimum reflection loss (RLmin) of −36.01 dB, with an effective absorption bandwidth (EAB, corresponding to the bandwidth of RL < −10 dB) of 12.75 GHz. These results were obtained when the unit cell had a side length of 22.5 mm, the slab thickness was 1.5 mm, and the cube had a thickness and edge length difference of 2.5 mm and 4.0 mm, respectively. Furthermore, the value of EAB is greater than 10 GHz for both transverse electric (TE) polarization and transverse magnetic (TM) polarization when the incident angle changes from 0° to 50°. The broadband and efficient EM wave (EMW) absorption characteristics of this absorber can be attributed to integration of excellent impedance matching and the multi-scale loss mechanisms.

A parallel piezoelectric micro-perforated panel absorber with flexible acoustic characteristics

In this paper, the sound absorption characteristics of a parallel micro-perforated panel absorber (MPPA) fabricated from polyvinylidene fluoride (PVDF) piezoelectric film are studied under an alternating voltage excitation. The simulation and experimental results show that when a certain frequency of AC voltage is applied to the parallel micro-perforated panel, the sound absorption characteristics of the MPPA at the excitation frequency can be improved due to the electrically induced vibration. With an increase in the alternating voltage amplitude, the improvement in sound absorption characteristics is more obvious. Therefore, the sound absorption coefficient of parallel PVDF-MPPA in the target frequency band can be improved by adjusting the parameters of excitation voltage reasonably. Based on the convenience of voltage regulation, this method is very suitable for suppressing the noise of the main frequency fluctuation without changing the structural parameters of the absorber. More importantly, the parallel PVDF-MPPA can apply voltage excitations of different parameters simultaneously, which is beneficial to improve the sound absorption effect in a wider frequency band. This study may provide a reference for the design of intelligent absorbers, especially for noise reduction structures in narrow spaces.

Synchronous manipulation of heterointerfaces and atomic hybrids in bimetallic MAX phase composites for advanced electromagnetic wave absorption

Rational constructing multi-phase interfaces and hetero-substituted sites structures holds extraordinary potential for harnessing tailorable electromagnetic (EM) responses and fascinating EM wave absorption. Herein, a series of new bimetallic MAX phase hybrid composites (Ti1-xVx)2AlCf with diverse dielectric behaviors integration are synthesized via a simple thermally driven gradient sintering strategy, using carbon fiber as the initial carbon source. Their chemical compositions, physical structures and EM properties are studied in detail, focusing on the resultant temperature and M-site vanadium atom substitutional engineering. Specifically, benefiting from the co-boosted interfacial/dipole polarization capabilities caused by the simultaneous manipulation of heterogeneous boundary states and intrinsic dipoles distribution at 1350 °C, the TiVAlCf composite exhibits an ultrahigh minimum reflection loss of −59.13 dB and an effective absorption bandwidth of 4.93 GHz, with a matching thickness of only 1.53 mm. Furthermore, multilayer gradient metamaterial model and a high-temperature tail nozzle model are constructed to further highlight the advanced EM functional application capacity of these MAX-based materials. This work is expected to provide an innovative platform for understanding cooperative multi-dielectric coupling mechanisms in the controllable design of high-efficient hybrid composite absorbers.

Design of graphene-based terahertz absorber and machine learning prediction model

In today's revolution of artificial intelligence, machine learning (ML) has come up with providing most rapid, accurate solution towards many complicated design problems. In this paper, a regression-based machine learning model has been developed, trained, and tested to forecast the performance of the Terahertz absorber. Different parameter variations of the dual circular ring Graphene FSS absorber viz., periodicity, thicknesses and radius of circular rings have been performed to attain maximum absorption of 99.9 % at center frequency 10.5 THz and bandwidth 1 THz (10.0 THz – 11.0 THz). The efficiency of nine different regression models (Keras regressor, Histogram gradient regressor, adaboost regressor, gradient boosting regressor, random forest regressor, decision tree regressor, k neighbours regressor, ridge regression, and linear regression) were tested against accurately predicting the absorption values and their performances were compared using R2 score and RSME. The study yielded very good R2 scores (near to 1.0) in case of random forest regression, thereby, demonstrating its effectiveness for future absorptivity prediction. The developed model considerably reduces time and effort in accurate prediction of the design parameters for THz absorber for any given absorptivity.

Design of an electromagnetic metallic metamaterial absorber for terahertz applications

Metamaterial absorbers have diverse applications in the terahertz range. In this paper, a metallic metamaterial absorber is designed to work as a narrowband, wideband, or ultrawideband according to application. A systematic method with minimal computational requirements for the design is developed. The method is efficient since the only information required is the operating frequency and required bandwidth. A condition for zero reflection which ensures matching with free space is derived. The proposed design method is used for the design of narrowband, wideband, and ultrawideband absorbers. For each case the design parameters are different. The narrow bandwidth is less than 5%, while the wide band lies between 5 and 20%, and the ultrawideband is larger than 20%. The dimensions of the designed structure and material properties (εr″) are different for each case. The designed absorber is wide-angle and polarization-independent. The sensitivity of the designed material due to changes of physical dimensions and permittivity is studied. To validate results, reflectivity and absorptivity are calculated using CST package. The dimensions obtained from the developed method are a bit modified using trial and error. The results from the developed method and CST are in excellent agreement.

Genetic algorithm-aided design of broadband near-perfect absorber with MoS2 film in the visible region

Broadband absorption plays a crucial role in the applications of optoelectronic devices. In this paper, we employ a genetic algorithm (GA) approach to enhance the absorption characteristics of an absorber comprising a MoS2 film enclosed within an antireflective coating and a one-dimensional Au grating supported by a gold mirror. An average absorptivity of 97.1 % is achieved for the optimized structure in the visible range (corresponding to wavelengths ranging from 400 nm to 800 nm). Finite element methods (FEM) and electromagnetic field analysis indicate that cavity resonances (CRs) and localized surface plasmon (LSP) resonances lead to absorption throughout a broad wavelength band. In addition, we verify the improved photoelectric response characteristics of the proposed absorber, which are significantly higher than the reference structures. Our approach is of importance for designing high-performance optoelectronic devices in the fields of photodetectors, modulators, solar energy and so on.

Investigation and Analysis of Graphene-Based Surface Plasmon Resonance Solar Absorber Design Using Au-GaAs-Cr Structure for UV and Visible Region

Investigation and Analysis of Graphene-Based Surface Plasmon Resonance Solar Absorber Design Using Au-GaAs-Cr Structure for UV and Visible Region

Design and analysis of a compact ultrathin penta-band metamaterial absorber

Design and analysis of a compact ultrathin penta-band metamaterial absorber

ANALYSIS OF CONSTRUCTIONS OF RECEIVED AMORTIZATION SYSTEMS

The theoretical research is devoted to the improvement of the existing structures of shock absorbers, which ensure the recovery of mechanical energy into electrical energy with further useful use. First of all, an analysis of the use of different shock absorbers by drive type was performed. The advantages and disadvantages of each of them are established according to the criterion parameters of reliability, manufacturability and operation. A refined classification of shock absorbers by type of kinematic connection and structural design is proposed. According to the proposed classification, the rational type of drive for creating new models of recuperative shock absorbers is determined to be hydraulic. According to the developed recommendations for choosing the shock absorber drive type, you can choose the drive type depending on the desired prevailing technical indicator. The paper presents the results of a theoretical study of existing designs of recuperative damping systems. It has been established that, in addition to energy recovery, such damping systems provide improved damping and damping performance and allow the user to choose the desired mode of operation of the suspension. Analysis of existing designs of regenerative shock absorbers indicates better efficiency of systems with feedback. This type of communication is provided in most cases by using electronic measuring systems with a control unit, which greatly complicates and increases the cost of the design. Based on the results of the theoretical analysis of the existing designs of recuperative shock absorbers of world manufacturers and developers, technical and technological requirements for new designs of recuperative shock absorbers were formed, which, in our opinion, are aimed at rationalization and optimization of the latter. According to the developed technical and technological requirements, a basic design scheme of a recuperative damping system with hydrovalves for improving quality parameters was developed. The principle of operation of the quality valve with a profiled spool window is described

Design and fabrication of a microcoil metamaterial absorber for the sub-terahertz region.

The development of electromagnetic wave absorbers operating in the sub-terahertz (sub-THz) region is necessary in 6G communications. We designed and fabricated a sub-THz metamaterial absorber based on metal microcoils embedded and periodically arranged in a dielectric substrate. The microcoil parameters were optimized by calculating the electromagnetic response of the metamaterial using finite element analysis. An actual metamaterial was then fabricated based on the optimized parameters and characterized using THz time-domain spectroscopy. Our microcoil absorber exhibits an absorptance of >80% and a high shielding performance at about 250 GHz. The resonance frequency can be precisely adjusted by modifying the microcoil array dimensions.

Thermally active programmable metamaterials with holey tilted struts

Bistable transition is often applied in the design of microstructures in metamaterials. In this study, we introduce a series of strategically placed holes in the tilted struts, and observe, through numerical and experimental analysis, an effect of the perforation on the snap-through buckling behavior of the structure. By infilling the holes with thermal-sensitive polymer bars, we realize actively tuning the local stiffness of the holey struts, thereby enabling a means to switch the metamaterial between bistable and monostable states. Furthermore, we propose a multi-stable metamaterial by stacking bistable units with different arrange of infilled and empty holes. The designed metamaterial demonstrates a progressive restoration from the deformed shape to its original shape as the environment temperature reaches up to certain values. These findings highlight the potential of holey-type bistable metamaterials in the design of actuators, deployable structures, and reusable energy absorbers.

Optimization design and analysis of the broadband acoustic absorber of the microperforated panel with an interpolated straight tube

The microperforated panel (MPP) structure is widely used in the field of noise reduction. The traditional MPP structure has a fixed absorption peak, and the optimized MPP structure has an improved absorption band, but the frequency range of the absorption is not ideal. For the design of broadband absorption in MPP structures, this paper presents a MPP acoustic absorber structure (N-MH) with an interpolated straight tube (IST) designed for superior broadband acoustic performance. The N-MH structure combines the advantages of the MPP and the embedded necked Helmholtz resonator, as well as having a sub-wavelength thickness of only 60 mm, which is only 1/14th of the wavelength at the first resonant frequency. The N-MH structure is optimized based on the particle swarm optimization (PSO) algorithm. In comparison to traditional microperforated panel structures, the N-MH structure exhibits a significantly broader sound absorption frequency band. Additionally, we thoroughly investigate the factors influencing the mid-low-frequency sound absorption performance of the N-MH structure. Through theoretical prediction, simulation analysis, and experimental testing, it is verified that the N-MH structure has excellent broadband sound absorption characteristics in the frequency interval of 0–2000 Hz, and the percentage of sound absorption bands with absorption coefficients exceeding 0.9 can reach 78.2%.

ANALYSIS OF CONSTRUCTIONS OF TORSION SHOCK ABSORBERS DRILLINGCOLUMN OSCILLATION

Designs of shock absorbers of torsional vibrations of the drilling columnare considered. According to the material of the node that perceives vibrations, the following are distinguished: devices with rubber (or other elastic) elements and devices with metal and rubber-metal elements. The design features of nine devices which allowthe vibrationlevel reduction of the rock-destructive tool, were analyzed.

Optimal design for a perforated panel absorber combined with Helmholtz-resonance and plate vibration

This study proposes a perforated panel sound absorber combined with Helmholtz-resonance and plate vibration and its optimal design method to broaden the sound absorption characteristics. The proposed perforated absorber has a simple structure consisting of a flexible panel with a hole and an air cavity. The conventional optimal design theory of the dynamic vibration absorber is applied to the perforated absorber. The proposed absorber is designed so that the acoustic impedance density will be equalized and almost minimized at two points independently of the damping of the panel. Optimal parameters are related to the Helmholtz-resonance frequency, the natural frequency of the panel, and the loss factor of the panel. The absorber with the optimal parameters was fabricated, and the sound absorption coefficient was measured using an acoustic impedance tube. The experimental results shows that the proposed method can effectively design the perforated panel absorber with the broadband sound absorption characteristics.