Structure Absorption Research Articles

Exploring the carbon-chain structure-activity relationship of CO2 and ketone-based absorbents

With regard to the physical absorbents for CO2 removal, the alteration of carbon-chain structure may benefit the CO2 absorption performance. However, the relationship between the carbon-chain structure of ketones absorbents and their CO2 absorption capacity has rarely been studied, and the related mechanism is unclear. In this study, theoretical calculations and thermodynamic experiments were carried out to explore the effects of the carbon-chain length and isomerism of ketones on their CO2 absorption performance. The density functional theory (DFT) simulations show that the F-∥ configuration is more stable than the others for the CO2+ketone complex in most cases. The followings are obtained according to the experimental results, which are pretty consistent with DFT calculations. The dissolution of CO2 in the ketone is a typical physical process. As the number of carbon atom increases, the CO2 absorption capacity of straight-chain ketones increases. Straight-chain ketones exhibit higher CO2 absorption capacity than branched-chain ones. The effect of increasing carbon-chain length and isomerism on CO2 absorption capacity are both stronger for the ketones with fewer carbon atoms; the influence mechanism can be attributed to different degrees of weak hydrogen-bond interaction between CO2 and ketone molecules, suggested by the DFT simulation results. The above conclusions are beneficial for the development of potential CO2 capture absorbents. In addition, the industrial application feasibility of surveyed ketone absorbents is also discussed.

Experimental study on crashworthiness and lightweight of cutting-type energy-absorbing structure of magnesium alloy for trains

Cutting-type structures, because of their desirable mechanical characteristics, high energy absorption capabilities and excellent guiding performance, has been extensively employed in high-speed trains. Its lightweight design and optimization problems are also the hotspot of research directions in present. This paper designed a new-type structure, i.e., magnesium alloy cutting-type energy-absorbing structure (CTEAS), taking into account its excellent properties of high lightweight level and ease of processing demonstrated through AZ31B magnesium alloy tensile mechanical test. Subsequently, experimental study on magnesium alloy CTEAS are conducted by trolley impact tests of train considering different cutting depths and different velocity levels. The results confirmed the outstanding advantages, including high lightweight level and higher absorbed energy properties, and lower demands of knives, compared with the structures with Q345 steel. In addition, the mechanism of knives cracking and melting phenomenon found in the experiment is explored by finite element analytical method. The results show that the temperature difference between the high-temperature surface and the interior during the cutting Q345 steel process is maybe the key influencing factor leading to knives damage. This research provides an effective tool for the design and analysis of excellent performance energy absorbing structure of high-speed trains.

Ultra wideband tunable terahertz metamaterial absorber based on single-layer graphene strip

In this paper, a terahertz absorber based on monolayer graphene is proposed. Compared with other absorber structures, the structure is very simple, which is conducive to the realization of the actual processing technology; in addition, the pattern of the absorber presents a certain combination of regularity, and certain research has been carried out, which provides a certain reference for the subsequent research related work. In particular, the pattern creatively proposes a structure based on the combination of patterns, which has a certain regularity and is more valuable for research than other absorbers. The absorber is capable of three-peak broadband absorption in the terahertz band and high absorption (absorption >0.9) over 3.39 THz in the frequency range of 1.53–4.92 THz. The feasibility of the combined modes is verified by structural delineation, and it is shown that the graphene-based designed and prepared absorber has good performance. In addition, the absorption mechanism of the absorber is illustrated by analysing individual modes and combinations. Furthermore, by tuning the Fermi energy level, the absorber exhibits absorption specificity, with the best absorption effect when = 0.7 eV. This finding suggests that the absorber may have better applications in the detection field. In addition, experimentally, we found that the absorber can maintain the stability of its absorption efficiency when the incidence angle of the electromagnetic wave changes slightly. By varying the physical parameters of the absorber, it is found that the absorber has excellent tolerance. The absorption performance remains stable when the physical parameters of the absorber are changed slightly. Finally, we investigated the effect of the physical parameters of the dielectric layer on the absorber and obtained the best overall performance at H = 18 um. Overall, the absorber shows good absorption, stability, and tolerance in the terahertz band, and this broadband absorber should have wide applications in terahertz absorption as well as in novel optical devices. Due to the good performance of this absorber, it has potential applications in smart switches, stealth fighters, etc., in addition to applications in the field of energy absorption and new optical devices.

Impact responses of the steel-PU foam-concrete-tube multilayer energy absorbing panel: Numerical and analytical studies

The enhancement of structural protection can be achieved by using energy absorbing structures as sacrificial layers. In this study, a new steel-PU foam-concrete-tube multilayer energy absorbing panel (SFCTMEAP) is developed to improve the impact resistance of buildings and infrastructures, and its behaviour under impact loading is numerically and analytically studied. A Finite Element (FE) model is established using LS-DYNA to further study the behaviours of SFCTMEAP, and its results (including the failure mode, displacement–time and impact force–time curves) agree well with the test data. The SFCTMEAP presents a deformation mode of local indentation of the front energy absorbing layer, flexure of the steel-concrete-steel panel and collapse of PU foam-filled steel tubes (PUFSTs). The energy dissipations of variant components of the SFCTMEAP are obtained through the FE model and the PUFSTs is the main energy absorbing component. In addition, parametric studies are performed to obtain the influences of the impact location, initial momentum of impactor and thickness of PU foam panel on the response of SFCTMEAP. The results indicates that the specimen with larger impact eccentric distance dissipates less impact energy, and raising the initial momentum of the impactor is benefit to the energy dissipation by the PUFSTs. Moreover, an analytical model is developed to calculate the displacement history of SFCTMEAP under the impact loading. The displacement responses predicted by the analytical model are found to be in good agreement with the test results.

Constructing 3D heterogeneous flower-like spherical MoS2/CNTs composites with worm-like surface as a superior electromagnetic wave absorber

Three-dimensional (3D) heterogeneous flower-like spherical MoS2/CNTs composites with worm-like interfaces were successfully fabricated by a simplified solvothermal reaction to achieve superb electromagnetic wave absorption (EWA) properties. The microstructure characteristics, morphology features, EWA performance and associated mechanism of as-prepared specimen were systematically analyzed. The incorporation of MoS2 resulted in the establishment of a 3D conductive network and a substantial augmentation of the heterogeneous interfaces between MoS2 and carbon nanotubes (CNTs), thereby inducing an amplified conductance loss and polarization loss, respectively. Moreover, the fabrication of 3D architecture not only enhances the structural robustness of the composites, but also broadens the avenue for electromagnetic wave (EW) reflection and scattering, thus augmenting the absorption of EW energy. As a result of the synergistic effect of augmented attenuation capability as well as optimized impedance matching, the EWA performance of materials was outstanding, with a minimum reflection loss (RLmin) of −52.1 dB and an effective absorption bandwidth (EAB) of 1.93 GHz achieved at a thin thickness of 2.46 mm in the X band. This research will serve as a meaningful point of reference for exploring 3D flower-like spherical structure of EW absorber.

Vanadium dioxide-based ultra-broadband metamaterial absorber for terahertz waves

An ultra-broadband, polarization-insensitive terahertz metamaterial absorber based on vanadium dioxide resonance structure is proposed in this paper. The device boasts advantages such as a straightforward design, broad absorption bandwidth, and substantial fractional bandwidth. Numerical simulations show that vanadium dioxide enables the absorber to achieve near-perfect absorption (with a rate greater than 95%) in its metallic state. It demonstrates an average absorption rate exceeding 96.5% across an ultra-broadband range (4.02 THz to 11.95 THz). The absorption bandwidth reaches 7.93 THz, with a relative bandwidth of 99.3%, representing a notable improvement over comparable absorbers. Furthermore, due to its highly symmetric pattern design, the device exhibits excellent polarization insensitivity and maintains stability even within a wide incident angle range. The operational mechanism of the absorber is elucidated through the application of impedance matching theory and near-field distribution analysis. The designed absorber structure makes vanadium dioxide materials more widely applicable in terahertz and ultra-broadband absorber devices, holding promising application prospects in fields such as security imaging, energy harvesting, and so on.

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

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%.

Numerical analysis of the Brewster-electrical duo-effect for multi-resonance tuning in THz absorber

The excitation and tuning of multiple resonances with narrow spectral width based on Brewster's effect is possible in an ultrathin dual-band terahertz absorber. The angular variation establishes a monotonic relation with the frequency of some generated resonances offering tunability. Moreover, burying a graphene ring resonator beneath the metallic ring splits the resonance for providing the triple narrow absorption windows. The electrical modulation offers the feature of independent tunability in the generated third absorption band. Thus, the frequency ratio of the upper to lower spectral absorption peak can be modulated by the electrically tunable Fermi energy of graphene. Engraving the graphene resonator also enhances the incident angle based tunability by affecting a greater number of Brewster generated resonance peaks. The narrow line shape of the triple band absorption can enable refractive index sensing and the detection of extraneous elements in localized analyte samples. The detection of imidacloprid pesticide in wheat flour is performed by the implemented sensor. The numerical analysis is done for the design and analysis of the absorber structures to report the above facts.

Fabrication of multi-layer radar absorbing structures based on continuous fiber 3D printing and thickness correction method

Three-dimensional (3D) printing technology has revolutionized the fabrication of complex geometries, including electromagnetic wave absorbers. In this study, the multilayer radar absorbing structure (RAS) was designed and fabricated using a continuous fiber 3D printing process based on material extrusion (ME). However, a large thickness error occurred during the 3D printing process. The thickness error in the multilayer RAS, which is a resonant electromagnetic wave absorber, causes a large error in the electromagnetic wave absorption performance. To address this issue, the thickness correction method based on unit thickness was proposed. The unit thickness, which is the basic thickness of the multilayer RAS, was calculated to account for the thickness increase during printing. The redesigned RAS based on the calculated unit thickness effectively corrected the thickness error. The total thickness and thickness of each layer of the corrected RAS were measured and found to be similar to the design value. The measured electromagnetic wave absorption performance closely matched the analyzed value, confirming the effectiveness of the unit thickness-based correction method in improving the ME-based 3D printing process for fabricating RAS.

A fast hemostatic and enhanced photodynamic 2-dimensional metal-organic framework loaded aerogel patch for wound management

Achieving rapid hemostasis and highly effective antibacterial holds significant importance in the early-stage treatment of wounds. In this study, a hybrid aerogel patch comprising carbon quantum dots (CQDs) modified 2-dimensional (2D) porphyrinic metal–organic framework (MOF) nanosheets was designed by incorporating gelatin methacrylate (GelMA) and polyacrylamide (PAM) based matrix. On one hand, CQDs were stably doped onto the surface of the 2D MOF nanosheets, thereby enhancing the photodynamic activity through fluorescence resonance energy transfer (FRET) process. After the preparation of hybrid aerogel patch, the patch loaded with CQDs-doped 2D MOF exhibited excellent photodynamic bactericidal activity against Gram-positive Staphylococcus aureus (>99.99 %) and Gram-negative Escherichia coli (>99.99 %). On the other hand, the hybrid patch with highly porous and absorbent structure can rapidly absorb blood to aggregate clotting components and form a hydration barrier covering the wound to enhance hemostasis. Besides, the hemolysis and cytotoxicity assays demonstrated a good biocompatibility of this designed patch. In summary, this 2D MOF-loaded aerogel patch holds a potential to achieve rapid hemostasis and effective anti-infection in the early-stage treatment of traumatic wounds.

Global rigorous coupled wave analysis for design of multilayer metasurface absorbers.

In this work, a novel Global NV-ETM RCWA method is proposed to accelerate the optimization of the periodic stepped radar absorbing structure. This method is based on the rigorous coupled-wave analysis (RCWA) utilizing the normal vector field (NV) and enhanced transmittance matrix (ETM) approach. The NV field dramatically improves the convergence rate for both dielectric and magnetic metasurfaces. The Global NV-ETM RCWA algorithm is developed to further accelerate the complete search calculations. Using the proposed method, the periodic stepped radar absorbing structures are efficiently optimized to realize the entire band absorption in 2-18 GHz. The optimization results demonstrate the Global NV-ETM RCWA method significantly increase the computational efficiency, with a 38-fold improvement over direct NV-ETM RCWA calculations when the truncation order N=3. This method provides a powerful tool for designing metasurface absorbers with various desired functionalities.

Ultra-thin metal-free terahertz absorber for electromagnetic shielding

An ultrathin broadband absorber covering the frequency range of 0.1 to 10 terahertz (THz) and to THz with more than 80% and 90% absorption, respectively is designed and numerically analysed. The absorber structure utilizes a partial reflecting surface and reflector of graphene separated by a thin dielectric spacer providing the metal-free structure. Multiple resonances are generated in the absorber structure whose spectrum can be separated or merged to find the narrow or broad absorption spectrum. The proposed absorber operates with the combine effect of the electromagnetic (EM) resonances occurring in the graphene resonator and the destructive interference taking place in the dielectric spacer. The absorber operation is validated through the theory of electromagnetic coupled mode resonances and with the theory of multiple reflections. The narrow absorption peaks can allow the proposed absorber to be utilized as refractive index sensor and the broad absorption spectrum can allow it to be utilized in the EM shielding and packaging applications.

Design, construction and commissioning of a technological prototype of a highly granular SiPM-on-tile scintillator-steel hadronic calorimeter

The CALICE collaboration is developing highly granular electromagnetic and hadronic calorimeters for detectors at future energy frontier electron-positron colliders. After successful tests of a physics prototype, a technological prototype of the Analog Hadron Calorimeter has been built, based on a design and construction techniques scalable to a collider detector. The prototype consists of a steel absorber structure and active layers of small scintillator tiles that are individually read out by directly coupled SiPMs. Each layer has an active area of 72 × 72 cm^2 and a tile size of 3 × 3 cm^2. With 38 active layers, the prototype has nearly 22,000 readout channels, and its total thickness amounts to 4.4 nuclear interaction lengths. The dedicated readout electronics provide time stamping of each hit with an expected resolution of about 1 ns. The prototype was constructed in 2017 and commissioned in beam tests at DESY. It recorded muons, hadron showers and electron showers at different energies in test beams at CERN in 2018. In this paper, the design of the prototype, its construction and commissioning are described. The methods used to calibrate the detector are detailed, and the performance achieved in terms of uniformity and stability is presented.

Performance enhancing solar energy absorber with structure optimization and absorption prediction with KNN regressor model

We used the honeycomb resonator structure and explored its absorptance response in the visible, ultraviolet, to mid-infrared regions. In this solar spectrum range, the average absorption is greater than 90%. In addition, the spectral absorption is 97.69%, 96.35%, 94.45%, and 96.11% in the respective solar spectrum regions, respectively. In this work, we observed the highest absorption response of the solar spectrum. Further, the KNN regressor model is employed for behavior prediction of the proposed absorber structure and results indicate this model highly predicts the absorption values for lower K values. This proposed model due to its ideal characteristics can be employed for a vast range of applications including performance improvement of solar cells, thermophotovoltaics, and many more.

Simulated and Experimental Research on Highly Efficient Sound Absorption of Low‐Frequency Broadband Acoustic Metamaterial Based on Coiled‐Up Space

Acoustic metamaterials are broadly employed in vibration and noise reduction fields for large defense industrial equipment such as engines and compressors thanks to their excellent subwavelength characteristics and extraordinary acoustic performance. However, the low‐frequency broadband sound absorption remains a thorny challenge in the scientific and engineering communities. This paper focuses on the low‐frequency broadband acoustic metamaterial composed of eight spiral absorbers coupled in two rows, researching its thermoviscous dissipation and sound absorption mechanism, and further analyzing its sound absorption characteristics. In the frequency range of 510–990 Hz, the average sound absorption coefficient of acoustic metamaterial with sound absorption area ratio of 2.72% reaches 0.80, and the cross‐sectional height is only 34 mm, which achieves the tradeoffs between structural thickness, frequency bandwidth and sound absorption performance. Furthermore, continuous and highly efficient broadband sound absorption within the target frequency band in practical applications can be achieved by optimizing adjustable parameters. In addition, finite element simulations are verified by experiments, which presents good agreement. Compared with traditional sound absorbing structure, the low‐frequency broadband acoustic metamaterial proposed in this paper owns the characteristics of small size and easy processing, which has broad application prospects in the field of low‐frequency noise control engineering.

Thermal conversion of solar radiation for possible applications in industrial heat convertors

The proposed solar thermal absorber consists of sandwich structure-inspired Ti–SiO2–Ti (Titanium–Silicon Dioxide -Titanium) Metal-insulator-Metal (MIM) material. Here proposed thermal absorber has materials, Ti as ground, SiO2 as substrate and Ti as resonator. The design of solar thermal absorber is well-versed with the modern theory of absorption and made up on a nanometre basis with each parameter being less than 500 nm. An average absorption of 96.34 % has been achieved throughout the wavelength range of 0.2–3 μm including various regions including UV, Visible, NIR, and MIR with an average absorptance 92.72 %, 93.81 %, 96.58 %, 98.55 % respectively. The proposed nanoscale solar absorber also has 1920 nm of wavelength range above 95 % with an average absorptance of 97.985 % and 2730 nm of wavelength range above 90%with an average absorptance of 96.6 %, although transverse electric (TE) and magnetic (TM) modes achieved an average absorptance of 96.34 % and 94.1 % respectively. We also have noticed characteristics like large angular and polarization-independent in the proposed solar energy absorber structure which eventually benefitted the applications of optoelectronics.

Deep reinforcement learning for optimal sound absorbing structures design

Deep learning algorithms have demonstrated a tremendous success in designing structures that surpass human capabilities. Based on the recent achievements of deep reinforcement learning in surpassing human capabilities, this paper focuses on implementing these algorithms to design optimal configurations of solid and porous materials that achieve a broadband absorption within the frequency range of 300 Hz to 3000 Hz. We employ model-free approaches, specifically deep Q-learning, double deep Q-learning, and dueling deep Q-learning algorithms, to predict material configurations that optimize absorption without requiring expertise knowledge. From a 230×30 different material combinations, the deep reinforcement algorithms learn to predict configurations that yield optimal absorption in few hundred steps. We discuss further the superior performance of a dueling deep learning algorithm compared to the other two deep learning approaches and a heuristic approach, such as genetic algorithm. The proposed model-free algorithms enable the prediction of absorption performance for any material configurations without the need for expertise.

Dynamic tunable narrow-band perfect absorber for fiber -optic communication band based on liquid crystal

At present, most of the reported metasurface structure absorbers show that its working band cannot be regulated actively. In this study, a dynamic tunable narrow-band perfect absorption structure for fiber-optic communication band based on liquid crystal (LC) is proposed and studied. The structure is mainly composed of two effective tiers. The top tier gold array and the bottom tier reflective gold film, which are separated by a SiO2-LC dielectric medium interlayer to form a metal–dielectric–metal structure. Due to the unique optical properties of LCs, its index of refraction can be changed by adjusting the bias voltage and temperature, so as to adjust the resonance wavelength actively. The designed structure is analyzed by finite element method and the coupled mode theory is used to verify the analysis results. The designed structure has a 99.92% absorption effect in the most commonly used band of fiber-optic communication. Due to the symmetry of the absorber structure, the device is not sensitive to the polarization state of the excitation source. Moreover, the absorber exhibits an unusual dependence on the incident angle, which can be attributed to the anisotropy of the LC. Based on the dependence of incident angle, a plasma optical switch with large ON/OFF ratio (η) of 27.395 dB and nearly flawless modulation depth of 99.818% can be realized. It is believed that this structure can provide a method for the dynamic control of near infrared electromagnetic waves, and to be applied in electromagnetic energy absorption, filtering and plasma optical switch system.

A Wideband DNG Metamaterial Absorber with WS-Shaped Split Ring Resonator for X- and Ku- Frequency Band Applications

A novel compact microwave metamaterial absorber structure with a wide bandwidth is proposed. The absorber structure is designed on an FR4 substrate with a 2.4 mm thickness. The metamaterial absorber unit cell design consists of a combination of W and S-shaped structures in which splits are incorporated to have the effect of a split ring resonator. The proposed unit cell structure is designed to have a wide absorption band, which includes the X and Ku frequency bands. The optimized dimension of the unit cell is 0.071 λ 0 × 0.71 λ 0 where λ 0 is the wavelength of the center frequency of the absorption band. The WS-shaped structures are oriented to absorb TE and TM waves for a wide range of polarization angles. The simulation results of the unit cell have shown absorption above 95% from 10.48 to 13.28 GHz. In addition, the absorber has an efficiency above 92% for incidence angles from 0° to 60° for fixed polarization. The unit cell structure and array are fabricated, and measurements are performed. The simulation and measured results have shown good agreement. The proposed metamaterial can be used in defense and radar surveillance applications.