Absorption Mode Research Articles

3D printing functionally graded metamaterial structure: Design, fabrication, reinforcement, optimization

The current study introduces a novel class of bio-inspired and 3D-printed metastructures called functionally graded lattice metamaterial beams (FGLBs). These lightweight lattice metastructures offer several benefits, including a high stiffness-to-weight ratio and excellent energy absorption efficiency. Therefore, their mechanical properties reinforced with AL-FRP (fiber-reinforced polymer) face sheets are aimed to examine through experimental testing and finite element simulation in the present work. An improved FGLB is also raised to expose the failure characteristics of graded metamaterial beams. The deformation mode, failure mechanism, and energy absorption of several 3D-printed graded metamaterial beam constructions were carefully explored. The results show that the bending behavior of the novel lattice beam is promoted mainly due to the reinforced structure, especially under mixing reinforcement of FRP and Al face sheets. Additionally, it is discovered that the geometrical parameters and metamaterial core graded direction have a substantial impact on the failure process and energy absorption of FGLB structures. Lastly, multiobjective optimization is used to identify the ideal FGLB design parameters. These accomplishments open the possibility of creating new classes of high-performance metamaterial structures by combining gradient design with additive manufacturing.

Effect of recycled oyster shell powder on hydration and strength development of magnesium phosphate cement

Using oyster shell powder (OSP) to prepare magnesium phosphate cement (MPC) not only reduces the pollution caused by the wasted oyster shell disposal, but also benefits the development of more environmentally friendly cement. The effect of OSP on the hydration and strength development of MPC was studied. An axial compression experiment including 45 cuboid specimens was executed to investigate the compressive strength, failure mode, stress–strain relationship, and energy absorption of MPC mixing with different mass contents (0% to 12%) of OSP over the curing times of 7, 14, and 28 days. Scanning electron microscopy, X-ray diffraction and energy dispersive spectroscopy were utilized for measuring the variation of MPC microstructure and hydration products caused by OSP. Results indicated that a new reactant CaHPO4·2H2O was formed, which optimized matrix strength. The substitution of OSP could reduce the cost of MPC by 2–9% without decreasing the strength. Compared with MPC without OSP, the compressive strength of the specimen with 3% OSP is increased by 6%. However, with the continuous increase of OSP, the compressive strength gradually decreases. Similarly, the elastic modulus of MPC increases first and then decreases with the increase of OSP.

Recommendations on Selecting the NPP Generator Transformer VA Rating

The specific features of selecting the VA rating of a nuclear power unit step-up transformer are analyzed. The analysis is based on the provisions of the international standard IEEE C57.116-2022, which is a guide for transformers connected to turbine generators, taking into account the definition of the term “transformer VA rating” according to Russian and European standards (GOST 16110-82 and GOST 30830-2002). The definition of this term in this guide differs from that adopted in Russia and the EU member states. An example of analytical calculation of the generator step-up transformer steady-state apparent power in the reactive power generation and absorption modes (turbine generator inductive and capacitive operation modes) is considered. The calculation is confirmed by the simulation results in the ETAR software package. The inexpediency of selecting the generator step-up transformer VA rating from the standardized range of rated capacities according to GOST 17544-85 and GOST 9680-77 is substantiated. An adverse effect of overestimating the transformer VA rating on the maximum three-phase short-circuit fault current in the generator voltage circuit (in the main electrical connection circuit section between the turbine generator and step-up transformer) of a nuclear power plant unit is shown.

Terahertz Metamaterial Absorber Based on Ni–Mn–Sn Ferromagnetic Shape Memory Alloy Films

Terahertz absorbers have been extensively investigated by researchers due to their applications in thermophotovoltaic energy conversion and sensors, but a key factor limiting their development is the lack of vital and versatile materials. Ferromagnetic shape memory alloys (FSMAs) offer a novel remedy for tunable metamaterials due to their brilliant recovery of deformation, remote control, and transient response. In this study, we propose a tunable absorber based on magnetic field tuning, consisting of Ni–Mn–Sn ferro-magnetic shape memory alloy films in fractal geometry and optically excited Si plates. Numerical analysis shows that the proposed absorber has an absorbance bandwidth of 1.129 THz above 90% between 1.950 THz and 3.079 THz. The absorber geometry can be regulated by an external magnetic field, allowing dynamic switching between broadband and narrowband absorption modes, the latter showing an ultra-narrow bandwidth and a high-quality factor Q of ~25.8. The proposed terahertz absorber has several advantages over current state-of-the-art bifunctional absorbers, including its ultra-thin structure of 10.39 μm and an additional switching function. The absorption can be continuously tuned from 90% to 5% when the light-excited silicon plate is transferred from the insulator state to the metal state. This study presents a promising alternative strategy for developing actively regulated and versatile terahertz-integrated devices.

Adjustable Trifunctional Mid-Infrared Metamaterial Absorber Based on Phase Transition Material VO2.

In this paper, we demonstrate an adjustable trifunctional absorber that can achieve the conversion of broadband, narrowband and superimposed absorption based on the phase transition material vanadium dioxide (VO2) in the mid-infrared domain. The absorber can achieve the switching of multiple absorption modes by modulating the temperature to regulate the conductivity of VO2. When the VO2 film is adjusted to the metallic state, the absorber serves as a bidirectional perfect absorber with switching capability of wideband and narrowband absorption. The superposed absorptance can be generated while the VO2 layer is converted to the insulating state. Then, we introduced the impedance matching principle to explain the inner mechanism of the absorber. Our designed metamaterial system with a phase transition material is promising for sensing, radiation thermometer and switching devices.

Terahertz Selective Active Electromagnetic Absorption Film Based on Single-layer Graphene

In this paper, a terahertz selective active electromagnetic frequency absorption film based on single-layer graphene is proposed. The film can achieve electromagnetic wave absorption rate higher than 0.9 at 2.4-4 THz and 7-8.6 THz in the THz band. And, through parameter inversion analysis of the relative impedance, it is found that the relative impedance of the film in the strong absorption part matches the free space impedance, which is consistent with the classical theory. The absorption mechanism of the high absorption of the film is also studied by analyzing the electric field distribution and the pattern changed simulation of graphene. The film has good stability at different incident angles and shows strong polarization incoherence. The characteristics of the film can be tuned by tuning the physical parameters, graphene Fermi energy and relaxation time. Interestingly, under some parameters, the film will change the original absorption mode. This paper introduces five absorption modes: double bandwidth absorption mode, two different single bandwidth absorption mode and two different double peak and bandwidth absorption mode. To sum up, the film has strong application value in aerospace, military, medical and other fields.

Control of the Deformation Mode of Aluminum Foam-Filled Tubes as a Function of Foam Porosity

This paper focuses on the computational modeling of the crashworthiness performance of designed foam-filled thin-walled tubular structures under quasi-static compression loading. The studied foam sample is designed in SolidWorks using the ‘sphere subtraction method’ and implemented as a filler material in the thin-walled tube. The quasi-static compression was simulated by Abaqus software. The foam porosity is manipulated to enhance the crashworthiness performance of empty tubes. The deformation mode and energy absorption capability of the analyzed structures are introduced in detail. The numerical results showed that foam-filler material could change the deformation mode and improve stability during the compression process of thin-walled tubular structures. The number of lobes significantly increases when introducing the foam filler to the tube. These folds are affected by the foam porosity. Results also indicate that the total crushing load of the foam-filled tube is also a function of foam porosity, the mechanical response of the foam-filled tubes tended towards the response of the empty tube for a high porosity (P >85%), while for low porosity (P<85%) the mechanical response of the foam-filled tubes exhibits the three universal deformation characteristics of foams, namely, initial linear stage, extended plateau stage, and final densification stage. The main mechanical properties: collapse stress, plateau stress, and densification strain were obtained via the energy-efficient method for different configurations. The calculated mechanical properties exhibited a strong dependence on foam porosity. To give a quantitative description of the obtained quasi-static compressive properties, these properties are expressed as a function of foam porosity. The proposed formulas can easily recover the quasi-static compressive properties of the empty tube in the case of the absence of foam. The control of the compressive performance of foam-filled tubes as a function of porosity allows for finding an optimum geometry with a predefined foam porosity value adjusted for a given application.

Study on the absorption technology of distribution network with high-proportion distributed power supply

Abstract In order to reduce energy dissipation and alleviate the energy crisis, this paper proposes an absorption mode of distribution network with distributed power supply. First of all, the starting power coefficient and cutting off power coefficient are set to reflect the efficiency of the inverter and obtain the active output power of the photovoltaic system. Then, the Gaussian iterative algorithm is used to calculate the power flow of the distribution network, which forms a model along with the branch switch to complete the variables optimization under the conditions that all power conversion elements are removed from the system and the security constraint is satisfied. Afterwards, through the apparent power of the distribution network node, the single feeder is transformed into two feeders to ensure the fixed voltage at the front end of the line and make the node voltage rise and exceed the limit. Meanwhile, the active power and reactive power are provided for distribution network to reduce the feeders voltage loss, the reasonable regulation measures are used to stabilize the voltage, and the constant power factor and voltage amplitude of the network connection point are added to address voltage over limit and lighten the influence of increasing distributed power on voltage rising. Finally, the size of voltage amplitude is referred to determine the reactive power, so as to realize reasonable absorption of distribution network. The analysis results show that the voltage regulation measures proposed significantly improve the overall absorption capacity of the power supply, with the capacity increased by 0.54MW and 0.2MW respectively.

Energy absorption and deformation modes of several thin-walled tubes under dynamic compression

Thin-walled tubes have shown extraordinary advantages in terms of light weight and energy absorbing impact scenarios. Based on hexagonal, re-entrant and square honeycombs, several new honeycomb thin-walled tubes were designed by reducing the wall thickness and increasing the number of webs with consistent quality. Low-velocity compression experiment and high-velocity impact finite element simulation were conducted on the honeycomb thin-walled tubes to study the effect of porous type on energy absorption and deformation behavior. Finite element model was established, and the finite element simulation results were verified with the experimental results. By comparing the thin-walled tubes with different porous types, the results show that the H0 has better energy absorption. The energy absorption of the re-entrant thin-walled tube is enhanced by adding web, and the RC has 38% higher energy absorption than the R0. The deformation modes of each structure were discussed and it was found that the thin-walled tubes of PLA material generally cracked at the fiber layer.

Parametric Study of PEKK Based Fiber Metal Laminates Used in Aerospace Applications

Numerical analyses offer a cost-effective and efficient alternative to experimental investigations, and Finite Element (FE) models have become a popular tool to simulate the behavior of Fiber metal laminates (FMLs) under impact loads. This study verified the reliability of the proposed FE models to predict the perforation response of ‎the FMLs investigated under low-velocity impact loadings. The validation of ‎the FE models was assessed through comparison with the corresponding results of the ‎experimental work. The results showed that the proposed simulations are capable of predicting the dynamic response of the laminates investigated with a high degree of success. The parametric studies were conducted on 2/1 titanium FMLs based on 2-ply composite cores and 2/1 aluminum FMLs based on 4-ply composite cores under impact with a variety of loading conditions. The developed FE models were then used to explore the structural behavior of the fiber metal laminates investigated with an extended variation of parameters, i.e., projectile striking angle, impact locations, the geometry of the projectile, and velocity. The results of the FE models are presented in terms of load-displacement traces, energy absorption, and failure modes. The findings of this study contribute to the understanding of the structural behavior of FMLs under impact loads and can inform the design and optimization of FMLs for various engineering applications. The use of FE models provides a cost-effective and efficient means of exploring the structural behavior of FMLs under different impact conditions, which can reduce the need for costly and time-consuming experimental investigations.

Hierarchical Codebook-Based Beam Training for RIS-Assisted mmWave Communication Systems

Reconfigurable intelligent surface (RIS) has emerged as a competitive solution to the blocking problem in millimeter wave (mmWave) communications. However, due to the passive nature of the RIS, obtaining channel state information (CSI) for RIS-assisted mmWave communication systems is rather difficult. Considering that the currently available RIS hardware cannot arbitrarily switch between the active (reflection with configurable phase response) and deactivate (absorption) modes, we suggest a new beam training method for RIS-assisted mmWave communication systems in this study. First, a predefined hierarchical codebook is created using the pattern synthesis method. Then, we provide a novel hierarchical beam training method using two multi-mainlobe codewords in each layer of the hierarchical codebook for beam sweeping. Combining the results of the beam identification in all the layers will yield the ultimate ideal beam direction. Theoretical analyses demonstrate that the suggested approach can effectively reduce training overhead while ensuring successful beam alignment. Simulation results show that the practical codebook can be created successfully, and the suggested method can achieve accurate beam alignment with reduced training overhead.

Crashworthiness of Additively Manufactured Lattice Reinforced Thin-Walled Tube Hybrid Structures

In this paper, a new hybrid structure of body-centered cubic lattice-filled thin-walled tube is designed, and the hybrid structure specimens of one-piece printing and split-printing are prepared by laser melting technique. The deformation mode and energy absorption characteristics of the new hybrid structure are investigated by experiments and numerical simulations. Under axial compression, the one-piece printed hybrid structure forms more wrinkles with smaller wavelengths, and the specific energy absorption increases by 12.14% compared with the split-printed structure; under transverse compression, the one-piece printed structure does not show the separation of the thin-walled tube from the lattice, and the specific energy absorption increases by 134.83% compared with the split-printed structure. It is worth noting that the designed hybrid structure has a 112.60% (580.15%) increase in specific energy absorption under axial compression (under transverse compression) compared to the empty tube. The effects of wall thickness, lattice density, and loading rate on the crashworthiness of the hybrid structure were investigated using a validated finite element model. This paper provides a new idea for the preparation of lightweight and high-strength energy-absorbing structures.

Electromagnetically induced transparency via localized surface plasmon mode-assisted hybrid cavity QED

In recent years, most studies have focused on the perfect absorption and high-efficiency quantum memory of the one-sided system, ignoring the characteristics of its optical switching contrast. Thus, the performance of all-optical switching and optical transistors is limited. Herein, we propose a localized surface plasmon (LSP) mode-assisted cavity QED system which consists of a Λ-shaped three-level quantum emitter (QE), a metal nanoparticle and a one-sided optical cavity with a fully reflected mirror. In this system, the QE coherently couples to the cavity and LSP mode respectively, which is manipulated by the control field. As a result, considerably high and stable switch contrast of 90% can be achievable due to the strong confined field of the LSP mode and perfect absorption of the optical medium. In addition, we obtain a power dependent effect between the control field and the transmitted frequency as a result of the converted dark state. We employ the Heisenberg–Langevin equation and numerical master equation formalisms to explain high switching, controllable output light and the dark state. Our system introduces an effective method to improve the performance of optical switches based on the one-sided system in quantum information storage and quantum communication.

The Influence of Reactive Power Control on the Turbine Generator Operational Reliability

The need to operate turbine generators in the reactive power absorption mode is stemming from a shortage of compensation devices in the grid. The operation of a conventional turbine generator as a reactive power compensator sometimes entails undesirable consequences for it. Recent years have seen a growing number of generator failures related to their prolonged operation at low excitation levels, which is the necessary condition for the generator to absorb reactive power. The article briefly describes the main factors that determine the relevance of the problem of reactive power control in the Moscow Region power system and the need to shift turbine generators for operation in the reactive power absorption mode. The article also provides information on the influence of operating modes in terms of reactive power control on the technical condition of the power plant main electrical equipment. The study is aimed at assessing the influence of reactive power control on the reliability of turbine generators. Based on a retrospective analysis of information on the technical condition of turbine generators and information about their damageability, recommendations on the possibility of using turbine generators for operation in reactive power absorption modes are drawn up. The operation of turbine generators in under-excitation modes eventually entails, regardless of their type and capacity, deterioration of the technical condition of the teeth of stator core end packages. In the absence of proper monitoring, fragments of crumbled sheets of active steel can cut through the stator winding case insulation, and the risk of its breakdown during operation or testing will increase. Under these circumstances, it is not possible to guarantee their reliable long-term operation.

A novel energy-absorbing composite structure with layers of basalt fiber fabric constraining waste brick particles and foam concrete

To seek a new way of recycling the waste brick, a novel energy-absorbing composite structure, consisting of the top layer of basalt fiber fabric constrained waste brick particles (BFCBP) and the bottom layer of foam concrete, is proposed to realize the purpose of the multi-level protection. First of all, the quasi-static compressive test is conducted on the BFCBP specimens with three different height-to-diameter ratios and the foam concrete specimens with four different densities and three height-to-diameter ratios, and their energy absorption performance is evaluated by the test data. The results show that the height-to-diameter ratio of the BFCBP specimen as well as the density and height-to-diameter ratio of the foam concrete specimen have a significant influence on their failure mode and energy absorption. Then after a reasonable combination of the two layers of BFCBP with a height-to-diameter ratio of 1.0 and foam concrete with a density of 700 kg/m3 and a height-to-diameter ratio of 0.5, the quasi-static and dynamic compressive tests are conducted on the energy-absorbing composite structure, and its deformation process, energy absorption, and load transfer under different compressive velocities are experimentally investigated. The test results show that the composite structure subjected to quasi-static and dynamic compressive loading demonstrates layered compression deformation and two-phase energy absorption characteristics, which implies that the proposed composite structure could provide multi-level protection by its staged energy absorption.

Detection of Carbon Monoxide’s 4.6 Micron Fundamental Band Structure in WASP-39b’s Atmosphere with JWST NIRSpec G395H

Carbon monoxide (CO) is predicted to be the dominant carbon-bearing molecule in giant planet atmospheres and, along with water, is important for discerning the oxygen and therefore carbon-to-oxygen ratio of these planets. The fundamental absorption mode of CO has a broad, double-branched structure composed of many individual absorption lines from 4.3 to 5.1 μm, which can now be spectroscopically measured with JWST. Here we present a technique for detecting the rotational sub-band structure of CO at medium resolution with the NIRSpec G395H instrument. We use a single transit observation of the hot Jupiter WASP-39b from the JWST Transiting Exoplanet Community Early Release Science (JTEC ERS) program at the native resolution of the instrument (R ∼ 2700) to resolve the CO absorption structure. We robustly detect absorption by CO, with an increase in transit depth of 264 ± 68 ppm, in agreement with the predicted CO contribution from the best-fit model at low resolution. This detection confirms our theoretical expectations that CO is the dominant carbon-bearing molecule in WASP-39b’s atmosphere and further supports the conclusions of low C/O and supersolar metallicities presented in the JTEC ERS papers for WASP-39b.

Oblique compression of square tubes with walls of different thicknesses

In this paper, thin-walled aluminum square tubes with three different types of wall thickness configurations were experimentally compressed at loading angles of 0°, 10° and 15°, i.e., four walls with uniform thickness (St1t1), opposite walls with the same thickness (St1t2O and St2t1O), and opposite walls with different thicknesses (St1t2A and St2t1A). Numerical analysis was further conducted to explore the effects of wall thickness, thickness configuration and loading angle on the deformation mode and energy absorption of tubes. The results show that tubes with opposite walls of different thicknesses (St2t1A) present better energy absorption performance than tubes with uniform thickness under oblique loading. In addition, tubes with opposite walls of the same thickness (St1t2O) absorb the most amount of energy under oblique compression at larger angles (20° and 30°).

잔향가변장치 적용에 따른 다목적 음악연습실에서 음환경 변화특성 평가

This study investigated the practical effects of the reverberation variable device on controlling reverberation time of the sound fields in a multi-purpose music practice room. The surface of the reverberation variable device can be changed to absorb or reflect the incident sounds by the integrated electronic control system. The developed devices was installed on the surfaces of a music practice room having a length and width of 13.5 m and 3.5 m, respectively, for practical verification. The reverberation variable devices in a total of 96 units were employed in the room with a surface area of 78 m2. Especially, 50 units and 46 units of device were installed on the walls and the ceiling, respectively. As a result, the maximum changed reverberation time by frequency bands was measured as 0.15 s at 125 Hz, 0.63 s at 250 Hz, 0.59 s at 500 Hz, 0.37 s at 1000 Hz, and 0.3 s at 2000 Hz. The reflection mode with all the reverberation variable devices in closed state showed the highest reverberation time of 1.29 s at 500 Hz. The sound absorption mode with all the reverberation variable devices in opened state showed the lowest reverberation time of 0.7 s at 500 Hz. According to the partial control, the reverberation time at 500 Hz was 0.89 s when half of the wall units were opened, and 0.81 s when the half of the ceiling units were opened. Additionally, the design application of the developed devices was examined in accordance with ISO 23591.

Mechanical Properties and Energy Absorption Abilities of Diamond TPMS Cylindrical Structures Fabricated by Selective Laser Melting with 316L Stainless Steel.

Triply periodic minimal surfaces (TPMS) are structures inspired by nature with unique properties. Numerous studies confirm the possibility of using TPMS structures for heat dissipation, mass transport, and biomedical and energy absorption applications. In this study, the compressive behavior, overall deformation mode, mechanical properties, and energy absorption ability of Diamond TPMS cylindrical structures produced by selective laser melting of 316L stainless steel powder were investigated. Based on the experimental studies, it was found that tested structures exhibited different cell strut deformation mechanisms (bending-dominated and stretch-dominated) and overall deformation modes (uniform and "layer-by-layer") depending on structural parameters. Consequently, the structural parameters had an impact on the mechanical properties and the energy absorption ability. The evaluation of basic absorption parameters shows the advantage of bending-dominated Diamond TPMS cylindrical structures in comparison with stretch-dominated Diamond TPMS cylindrical structures. However, their elastic modulus and yield strength were lower. Comparative analysis with the author's previous work showed a slight advantage for bending-dominated Diamond TPMS cylindrical structures in comparison with Gyroid TPMS cylindrical structures. The results of this research can be used to design and manufacture more efficient, lightweight components for energy absorption applications in the fields of healthcare, transportation, and aerospace.

Evaluation of quasi static strength of Kevlar/Basalt-Epoxy and Kevlar/Glass-Epoxy Intra-woven composite laminate

The competency in combining the best qualities of materials and high-performance characteristics of the composites results in its wide range of applications. This paper describes the estimation of quasi-static impact properties on Kevlar/Basalt (KB) and Kevlar/Glass fibre (KG) intra-woven 1 × 1, 3 × 3, and 5 × 5 composite laminates based on ASTM D6264 standards. The novelty of this work is the weaving methods used in the fabrication of composites as well as the pattern in which it is intertwined. The Kevlar and basalt are intra-woven by placing one fibre of Kevlar and one fibre of basalt, one over the other to form ‘1 × 1′ configuration (KB1x1). Similar approaches are followed to form the ‘3 × 3′ configuration (KB3x3) and ‘5 × 5′ configuration (KB5x5). The same pattern is followed for Kevlar/Glass fibre. The Kevlar/Basalt and Kevlar/Glass fibre are woven using the manual handloom weaving hybridization method. Quasi-static and impact tests on composites gives an idea on the energy absorption capability and modes of collapse as energy-absorbing capacity is the main requirements for aerospace and ballistic applications. Square-shaped specimens of size 100 mm by 100 mm are cut out from the original composite plates using vertical band saw machine. Specimens are tested using Universal Testing Machine and the values of load at peak in kN and flexural stress in N/mm2 are noted. The damage area of each specimen is observed and calculated. On comparing the data of various intra-woven Kevlar/Basalt (1 × 1, 3 × 3 and 5 × 5) composite laminates with intra-woven Kevlar/Glass fibre (1 × 1, 3 × 3 and 5 × 5) composite laminates, it is observed that Kevlar/Basalt composite laminate, namely KB3 × 3 and KB5 × 5 have higher impact strength. This is due to its superior load-carrying capacity than other laminates. Finally, based on the quasi-static impact property, Kevlar/Basalt KB3 × 3 intra-woven composite laminate reports a greater impact strength thereby offering itself as an alternate material for varied aerospace and ballistic operations.