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Triply periodic minimal surfaces (TPMSs) are found in many natural objects including butterfly wings, sea urchins, and biological membranes. They simultaneously have zero mean curvature at every point and a crystallographic group symmetry. A metamaterial can be created from such periodic surfaces or used as a reinforcement of a composite material. While a TPMS as a mathematical object has been known since 1865, only novel additive manufacturing (AM) technology made it possible to fabricate cellular materials with complex TPMS shapes. Cellular TPMS-based metamaterials have remarkable properties related to wetting/liquid penetration, shock absorption, and the absence of stress concentrators. Recent studies showed that TPMSs are also found in natural crystals when electron surfaces are considered. Artificial crystal-inspired metamaterials mimic such crystals including zeolites and schwarzites. These metamaterials are used for shock, acoustic waves, and vibration absorption, and as structural materials, heat exchangers, and for other applications. The choice of the crystalline cell of a material, as well as its microstructure, plays a decisive role in its properties. The new area of crystal-inspired materials has many common features with traditional biomimetics with models being borrowed from nature and adjusted for engineering applications. [ABSTRACT FROM AUTHOR]

Novel (La 0.2 Eu 0.2 Nd 0.2 Sm 0.2 Pr 0.2)(Al 0.6 Co 0.4)O 3-δ (HE-1) and (La 0.2 Eu 0.2 Nd 0.2 Sm 0.2 Ca 0.2)(Al 0.6 Co 0.4)O 3-δ (HE-2) high-entropy ceramics were synthesized via solid-phase reaction technology. These two ceramics simultaneously own excellent infrared radiation performance and low degradation. The mechanism of emissivity enhancement was investigated, and emissivity decay of ceramics heated at 1500 °C for various holding time was studied. The results verify that the synthesized ceramics have perovskite crystal structure. The emissivity values of HE-1 and HE-2 are 0.78/0.66 and 0.82/0.83 in the near/mid-infrared band, respectively. These IR emissivity values are much higher than that of pure LaAlO 3 , which is attributed to enhanced impurity absorption, free carrier absorption and lattice vibration absorption. Moreover, after heating at 1500 °C for 10 h, HE-1 and HE-2 ceramics appear extremely slower emissivity decay rate (1.2–4.5 %), in comparison with fast decay rate (25.5–36.8 %) of pure LaAlO 3. This phenomenon can be attributed to the hysteresis diffusion effect of high-entropy ceramics, which can inhibit grain growth and emissivity decay. The novel ceramics have important application prospect in long-term energy-saving for high-temperature industry. [ABSTRACT FROM AUTHOR]

In order to effectively reduce the vibration of the product in the process of transportation, the cushioning pad is applied in the packaging of the computer case, which can not only greatly reduce the cost of the cushioning packaging design, but also promote the sales of the product. The vibration response of the key components in the computer case was tested and analyzed under the conditions of force hammer experiment and random vibration experiment, and the direct transmission rate of the buffer liner system to the key components was obtained. The excitation of three vibration levels of the standard truck vibration spectrum was used to simulate the excitation of different intensities in actual transportation, and the excitation acceleration power spectrum was obtained. The direct transmission rate quantified the vibration transmission characteristics of each buffer pad to the key components, and the size of the direct transmission rate reflected the degree of vibration energy absorption of each buffer pad to the key components. The critical buffer pad was optimized to absorb more vibration energy by increasing the buffer area of the critical buffer pad, reducing its vibration transmission capacity in the main resonance area. [ABSTRACT FROM AUTHOR]

AbstractThis paper introduces a method for attenuating longitudinal elastic waves in metamaterial bars through the utilization of Dual-Action (DA) vibration absorbers equipped with multifrequency resonators (MFRs). The metamaterial bar (Metabar) is composed of a linear arrangement of evenly distributed and enclosed DA vibration absorbers connected to an isotropic bar. The DA vibration absorber is constructed with multiple spring-mass resonators interconnected with each segment of the isotropic bar at two points. An analytical methodology is formulated employing Finite Element Modeling (FEM) and Bloch’s theorem to demonstrate the existence of multiple stopbands, leading to the generation of broad and configurable frequency stopbands. The article illustrates the design and modeling of the metabar’s DA vibration absorber, showcasing analytically that the vibration suppression and, consequently, wave attenuation within the metamaterial bar are grounded in the fundamental principles of basic mechanical vibration absorption. The DA absorber effectively prevents longitudinal wave propagation through the metabar by generating two internal forces to counteract any incoming wave within the stopband frequencies. Furthermore, these internal forces can be adjusted by optimizing the effective properties of the DA vibration absorber. A comprehensive parametric investigation is then conducted to analyze how the properties of the enclosed MFRs of the DA absorber, such as mass densities and stiffness coefficients, influence the locations and sizes of the frequency stopbands. The results from FEM simulations show a substantial alignment with dispersion curves across various prescribed configurations, offering strong validation for the proposed metamaterial design that integrates the DA vibration absorber with MFRs. The introduced mechanism for vibration absorption and suppression is of significance in applications involving the control and manipulation of wave propagation. [ABSTRACT FROM AUTHOR]

Large-diameter polyvinyl alcohol (PVA) fiber has a broad application prospect in the field of reinforcing geomorphic building materials owing to its large diameter and excellent mechanical properties. In this work, PVA2499 polymer was used as the raw material, DMSO/H2O as the hybrid solvent, and the staged heating approach was adopted to obtain high solid content of spinning solutions, and then a series of large-diameter medium-strength PVA fibers with different solid contents of spinning solutions (SCS) were prepared by dry-wet spinning, and the Fourier transform infrared spectroscopy (FTIR), scan electron microscope (SEM), differential scanning calorimetry (DSC), thermal analysis (TGA), X-ray diffractometer (XRD) and electronic universal testing machine were performed to explore the effect of the SCS on the structure and performance of PVA fiber. The results displayed that with the increase of the SCS, the -OH stretching vibration absorption peak of PVA fiber moved from 3276 cm−1 to 3262 cm−1; The tensile strength, initial modulus, the crystallization and orientation of PVA fibers all increased first and then decreased. Especially, when the SCS was 23.5wt%, the diameter of the PVA fiber was 110.6 ± 6.0 μm (124.8 ± 6.2 dtex), the tensile strength was 7.0 ± 0.3 cN/dtex, the initial modulus was 106.2 ± 10.3 cN/dtex, the crystallization and the orientation were 49.6% and 96.8%, respectively. [ABSTRACT FROM AUTHOR]

Cellulose and its derivatives have been widely used in various applications. Cellulose can be isolated from sugarcane bagasse waste. This research aims to isolate and modify the sugarcane bagasse cellulose to improve its characteristics and usability. Cellulose was isolated using the alkalization and bleaching method, wherein the alkalization processes the biomass was immersed in a sodium hydroxide solution and bleached using hydrogen peroxide. Cellulose modification was performed using alkali treatment and etherification stages with monochloroacetic acid in an isopropanol solvent. The β‐(1,4)‐glycosidic vibration absorption on both the bleaching products at 896 cm−1 confirmed pure cellulose, while a carbonyl group at 1610 cm−1 in the modified cellulose product confirmed the pure CMC product. The CMC obtained had lower thermal stability in the interval 241.35–299.87 compared to cellulose as its source, indicating an increase in the amorphous region. According to experimental findings from the MB adsorption investigation, citric acid‐crosslinked sugarcane bagasse derivatives of carboxymethyl cellulose (CMC) were more effective adsorbents for removing MB than commercial CMC with the same formulation (2 : 1). The study's findings also indicated that an increase in the percentage of MB degradation was correlated with an effect of adsorbent dose and contact time. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile (PAN) fiber modification can promote the stabilization efficiency and mechanical properties of the subsequent carbon fibers; however, it could cause damage to the fibers to some extent. In this article, the effects of NaIO4 treatment on the chemical and physical properties of PAN fibers were investigated. After NaIO4 modification, the cyclization reaction has partially occurred, owing to the FTIR revealed that the C≡N peak was weakened, but the C=N stretching vibration peak, the –N = C=O stretching vibration peak, the C=O stretching vibration absorption peak, and the short sequence conjugate C=N characteristic peak were enhanced simultaneously, indicating a successful cyclization and dehydrogenation reaction. Moreover, owing to more oxygen-containing functional groups successfully attached to the PAN fibers and the cyclization reaction taking place, the initial temperature, peak temperature, and heat release of cyclization decreased, which means a more efficient and safer stabilization process. X-ray diffraction (XRD) showed that the (100) crystal plane microcrystal size was the smallest at 40 °C of the modification temperature, whereas the (002) crystal plane microcrystal size was the largest at 60 °C. The modified stabilized PAN fibers presented lower crystallinity and a more aromatic structure compared with untreated fibers. Raman spectra revealed a significant increase in the intensity of the G peak after NaIO4 modification; the R-value decreased from 1.65 to 1.43, demonstrating a transformation of the sp3 hybrid carbon structure into a more graphite-like sp2 hybrid C=C structure. Meanwhile, scanning electron microscopy (SEM) images disclosed additional grooves and cracks on the fiber surface after modification. [ABSTRACT FROM AUTHOR]

To better suppress low-frequency vibrations of flexible manipulators induced by the rotation of motors and eccentricity, a novel type of tuned particle damper (TPD) is designed by combining the advantages of classical dynamic vibration absorber (DVA) and particle dampers (PD). Compared to traditional DVAs, this TPD can reduce additional mass and effectively broaden the frequency band of the DVA. Firstly, an equivalent theoretical model is established to describe the frequency tuning principle of the designed TPD. Based on the theory of a single particle damper, the equivalent damping and stiffness of the particles are calculated through an approximate approach. Then, a three-degree-of-freedom vibration model of the manipulator system with the TPD is built, and the dynamical characteristic of the primary resonance for the coupled system are analyzed by the perturbation method. Finally, the experimental platform is set up to verify the theoretical results. A manipulator is applied to test the low-frequency vibration absorption of the designed TPD, and the vibration suppression effect is discussed both in theoretical analysis and experiments. [ABSTRACT FROM AUTHOR]

This study focuses on addressing the issue of unwanted vibrations commonly encountered in various fields by designing an Active Vibration Cancellation (AVC) structure using a flexible piezoelectric composite material macro fiber composite (MFC). A comparative performance analysis was conducted between the AVC and a traditional passive gel that continuously absorbs vibrations. The results showed that AVC was more effective in mitigating vibrations, making it a promising solution for vibration control. The results of this study from extensive vibration–sensing experiments and comparisons revealed that AVC effectively cancels the vibrations and vibration absorption performance of the passive gel. These findings underline the potential of AVC as an efficient method for eliminating and managing undesired vibrations in practical applications. Specifically, AVC demonstrated a high vibration cancellation ratio of approximately 0.96 at frequencies above 10 Hz. In contrast, passive gel exhibited a relatively consistent vibration absorption ratio, approximately 0.70 to 0.75 at all tested frequencies. These quantitative findings emphasize the superior performance of AVC in reducing vibrations to levels below a certain threshold, demonstrating its efficacy for vibration control in real-world scenarios. [ABSTRACT FROM AUTHOR]

Infrared radiation (IR) ceramics are generally recognized as energy-saving materials for thermal equipment. In this work, as novel infrared radiation ceramics, Co2+-doped LaAlO 3 ceramics were synthesized via a solid-phase reaction method, and the influence of the Co2+ doping concentration on the infrared emissivity of ceramics was systematically investigated. The original Al element position was replaced by Co in Co2+-doped LaAlO 3 , leading to lattice distortion, oxygen vacancy generation and the "Co2+→Co3+" transformation. The increase in doped Co content leads to enhanced impurity absorption, free carrier absorption and lattice vibration absorption, which significantly improve infrared emissivity. The average emissivity values in the 0.76–2.5 μm and 2.5–14 μm bands of the LaAl 0.6 Co 0.4 O 3-δ specimen (40 mol% Co) are 0.89 and 0.86 respectively, which are 324% and 28% higher than those of pure LaAlO 3. This novel Co2+-doped LaAlO 3 ceramic with high infrared emissivity has significant application prospects for energy-saving applications of thermal equipment. [ABSTRACT FROM AUTHOR]

This paper presents an approach to model the impact behaviour of a dual-acting magnetorheological elastomer (MRE) damper using 4th-order polynomial functions optimized with a gravitational search algorithm. MRE is a type of smart material that can change its mechanical properties in response to an injected current, making it well-suited for a wide range of applications such as vibration absorption, noise cancellation, and shock mitigation. The proposed model uses a combination of polynomial functions designed to predict the nonlinearity of MRE during compression and extension stages. The model is tuned and validated using experimental data from impact tests conducted on the MRE damper under various currents. The results indicate that the developed model can accurately track the impact behaviour of MRE with minimum error. Additionally, an interpolation model is proposed to estimate the appropriate forces for median currents. The interpolation model predicts the force between the upper and lower currents, demonstrating the model's ability to predict MRE behaviour accurately. The main contribution of this study is proposing a non-parametric model of MRE that is able to identify the hysteretic behaviour of the MRE based on specific current applied. In addition, an interpolation model is introduced in this study to cover not only the input current starting from 0 A to 2 A but also the intermediate current such as 0.3 A, 0.7 A, 1.3 A and 1.7 A. [ABSTRACT FROM AUTHOR]

The finite element method (FEM) using Ansys program (APDL) was used in this study to evaluate the idea of tuned vibration absorbers applied to a beam construction for the undamped system. The ideal location for the Dynamic Vibration Absorbers (DVAs) and their numbers to be installed on the fixed-fixed beam in order to lessen beam vibration was also investigated. The DVA was coupled to the fixed-fixed beam vibration node for three vibration modes. The natural frequency and frequency response of the beam were calculated in this study using modal and harmonic analysis, respectively. The vibrational characteristics of the F-F beam with and without DVAs were presented. The simulation results demonstrated that the vibration amplitude decreases in the presence of the DVAs and its reduction depends on the locations of the DVAs and its number. In addition, the attached DVAs affect the structural beam vibration. Depending on the modes of vibration, the vibrational peak is the optimal place to attach DVA. [ABSTRACT FROM AUTHOR]

Most natural materials have rotational and hierarchical properties, so they can show excellent mechanical properties such as shear resistance and impact resistance. In order to further improve the energy absorption characteristics of vibration absorbing structures, a new type of honeycomb structure with integral rotation and group rotation is designed and characterized. The effects of the geometrical parameters of rotation Angle on the impact deformation mode, stress response curve and energy absorption characteristics of the honeycomb structure are studied through numerical simulation and experimental design. The results show that the overall honeycomb performance of 15° is better than that of 0°, the specific energy absorption is the results show that the overall honeycomb performance of 15° is better than that of 0°, the specific energy absorption is increased by 6%, the bearing capacity is increased by 320 N, and the crushing force efficiency is increased by 2%. Compared with the whole cell and the group cell, the specific absorption energy increased by 35%, 73% and 71%. The results of this paper provide a new insight into the impact performance of monolithic and grouped rotating honeycomb structures, which is helpful for the results of this paper provide a new insight into the impact performance of monolithic and grouped rotating honeycomb structures, which is helpful for the optimization of crashworthiness structural design. [ABSTRACT FROM AUTHOR]

Wind turbine drivetrains play a fundamental role in converting wind power into electrical energy. The gearbox is one of the most important and expensive components in a wind turbine drivetrain. Since flexible suspensions mounted on the gearbox are mainly designed for isolating vibration transfer to other turbine components, the gearbox itself still suffers from complicated whole-body vibration. In view of this, a vibration absorption method based on modal interaction is put forward to alleviate the whole-body vibration of the wind turbine gearbox with flexible suspensions. A vibration absorber with adjustable control parameters is utilized to establish modal coupling with the wind turbine gearbox. Internal resonance is analyzed and used to construct a modal interaction mechanism between the vibration absorber mode and the controlled gearbox mode. With the help of modal interaction, the vibration energy of the controlled gearbox mode is successfully absorbed by the vibration absorber mode and effectively dissipated by the damping of the vibration absorber mode. Through numerical simulations and virtual prototyping simulations, its vibration alleviation performance is verified. Since the proposed method is designed in terms of the controlled mode of the wind turbine gearbox rather than external excitations, it is suitable for applications in a complicated working environment. Besides, the proposed method aims to transfer and dissipate vibration energy through nonlinear modal interaction rather than suppress vibration via external energy, and thus can effectively deal with strong vibration problems. More importantly, it can easily work together with the existing vibration isolation method and further alleviate the whole-body vibration of the gearbox. This research will contribute to improving the reliability and service life of wind turbine gearboxes. [ABSTRACT FROM AUTHOR]

Along with the living environment, organisms have evolved structures that adapt to specific environments and have better mechanical properties. Bioinspired materials learn from nature and improve their mechanical properties by imitating the structure of living organisms. Based on the 4D printed shape memory polymer and the bioinspired design method, this research proposes a soft and hard phase hybrid bioinspired metamaterial with shape memory effect and programmable mechanical properties. Compared with traditional nacre-like materials, bioinspired materials have adjustable characteristics of mechanical properties, impact resistance, and low-frequency vibration isolation. First, based on the constitutive relation of SMP (Shape memory polymer) material and its numerical simulation, an intelligent bioinspired metamaterial is designed. Subsequently, the mechanical properties and vibration isolation behavior and adjustability performance of multi-scale bioinspired metamaterials are explained by experiments. Finally, the adjustable functional mechanism of the deformation and vibration isolation of the bioinspired metamaterial is described. The research of these bioinspired metamaterials has broad application prospects in the fields of impact protection and low-frequency vibration absorption. [ABSTRACT FROM AUTHOR]

La 2 (Zr 1- x Sn x) 3 (MoO 4) 9 (0.02 ≤ x ≤ 0.10) (LZMS) materials were successfully synthesized to scientifically investigate the effects of Sn4+ addition on phase composition, microstructures, lattice vibration, and dielectric response at microwave frequency. XRD patterns indicate that all samples belong to the trigonal crystal (S.G. R-3c). The crystallite size and lattice strain were analyzed using the Willimson-Hall equation. According to the apparent density and SEM, the LZMS ceramics achieved a dense and homogeneous microstructure when sintered at 700 °C. Analysis of the microwave dielectric properties revealed that the ceramics with x = 0.06 sintered at 700 °C achieved excellent performances (Qf = 75,508 GHz, ε r = 10.18, τ f = −22.21 ppm/°C). The far-infrared reflectance spectrum shows that the theoretical permittivity of the ceramic was mainly from the absorption of phonon vibrations below 400 cm-1. Consequently, the La 2 (Zr 0.94 Sn 0.06) 3 (MoO 4) 9 ceramic has excellent microwave dielectric properties and can be used as a material for 5G communication devices. [ABSTRACT FROM AUTHOR]

The effectiveness of two ways to reduce the vibration and sound emission of a high-pressure laminate plate has been investigated. It has been found that the inclusion of viscoelastic polymer polyvinyl acetate film in the laminate structure or constrained damping layer treatment based on polyvinyl acetate film and aluminum foil or plastic leads to a significant improvement in its vibroacoustic characteristics. The greatest reduction in vibration and sound emission was achieved by applying a coating with aluminum foil whose thickness was six times less than that of the damped laminate plate. [ABSTRACT FROM AUTHOR]

This study is the first to investigate the effect of chaotic vibration on the sound absorption of a curved perforated panel. Previous studies on the effect of nonlinear vibration on the sound absorption of a panel absorber have focused on periodic responses only. In this study, a sound absorption formula was derived by considering the panel impedance and perforation impedance. The numerical integration method was adopted to generate various chaotic vibrational responses, which were used to compute the corresponding sound absorptions. Several interesting findings that have never been observed in any previous studies on acoustic absorption were derived. First, in the chaotic and highly nonlinear cases, as the excitation frequency increased, the corresponding response frequencies decreased. This was opposite to the typical trend in linear cases, in which higher excitation frequencies corresponded to higher response frequencies. Second, in chaotic cases, absorption mainly occurred due to panel vibration effects. This is also in stark contrast to the findings of studies on perforated vibrating panels, in which the absorption effect mainly originates from perforations. Additionally, the absorption bandwidths are much wider and can shift to higher frequencies; however, the peak absorption coefficients were approximately 20% lower than in the case of the perforation effect only. Third, in the quasi-chaotic case, the absorption curve in the case of the perforation effect plus the vibration effect was between the absorption curves of the perforation effect only and the perforation effect plus the vibration effect. [ABSTRACT FROM AUTHOR]

Dual-clutch transmissions (DCTs) are very sensitive to torsional vibration and easily produce rattle noise if a single-mass flywheel (SMF) with a conventional torsional damper or a dual-mass flywheel (DMFW) is used in the vehicle. Only a DMFW combined with a centrifugal pendulum vibration absorber (CPVA) can eliminate rattle problem; however, this solution is expensive. Alternatively, a SMF with a CPVA is proposed to eliminate the DCT rattle issue, which could be a feasible and cost-effective solution free of side effects introduced by DMFWs. The vibration absorption principle of different types of pendulums and the rotor dynamic model are investigated to study the feasibility of a SMF with CPVA in a DCT vehicle. A seven-degree-of-freedom nonlinear lumped torsional vibration model is proposed to evaluate the torsional vibration attenuation performance of different configurations of torsional dampers and CPVAs. As per the model calculation results, the bifilar pendulum features the best attenuation performance compared with the circular and cycloid pendulums. The effect of pendulum parameters on attenuation is studied, and the optimized values are obtained. The SMF and optimized bifilar CPVA combination can satisfy the no-rattle requirements in vehicle relative to the DCT in-vehicle no-rattle threshold. A vehicle assessment on roads using physical pendulum prototypes indicates that the SMF with CPVA can be used as an alternative, cost-effective solution for DCTs, instead of the expensive DMFW with CPVA solution. [ABSTRACT FROM AUTHOR]

High mechanical property poly (vinyl alcohol) (PVA) fibers have attracted tremendous attentions because of their excellent mechanical properties and has a potential application in the field of building enhancement. In this article, PVA polymer with high polymerization degree (Pn) and high Syndiotacticity-diad content (S-diad) were synthesized using vinyl acetate (VAc) and vinyl pivalate (VPi) as monomers via emulsion polymerization with water as solvent, the GPC and 1H NMR were used to characterized the Pn and S-diad of PVA polymer. Then the lanthanum chloride (LaCl3) was chosen as cross-linking and the synthesized PVA polymer as raw material for dry-wet spinning, a series of PVA fibers with high strength and high modulus have been prepared. The final PVA-La fibers were characterized through a series of experiments including of FTIR, SEM, DSC, TGA, XRD and fiber tensile tester. It turned out that the Pn and S-diad of synthesized PVA polymer were 4817 ± 76 and 56.3 ± 0.7%. With the increasing of LaCl3 content, the -OH vibration absorption peak of PVA-La composite fiber gradually increased from 3462 cm-1 to 3484 cm-1; the strength, modulus, crystallinity and orientation all increased first and then decreased. Especially, the properties of PVA-La fiber exhibited an optimal LaCl3 content of 0.8 wt%, the denier was 5.4 ± 0.5 dtex, the tensile strength and highest elastic modulus of 15.19 ± 0.5 cN/dtex and 369.21 ± 9.1cN/dtex, the elongation at break was 3.72 ± 0.4%, the crystallinity was 53.9 ± 0.6%, the orientation was 95.6 ± 0.6%. [ABSTRACT FROM AUTHOR]

In this study, a coupling model of fluid-conveying pipes made of functionally graded materials (FGMs) with NiTiNOL-steel (NiTi-ST) for vibration absorption is investigated. The vibration responses of the FGM fluid-conveying pipe with NiTi-ST are studied by the Galerkin truncation method (GTM) and harmonic balance method (HBM). The harmonic balance solutions and the numerical results are consistent. Also, the linearized stability of the structure is determined. The effects of the structure parameters on the absorption performance are also studied. The results show that the NiTi-ST is an effective means of vibration absorption. Furthermore, in studying the effect of the NiTi-ST, a closed detached response (CDR) is first observed. It is noteworthy that the CDR may dramatically change the vibration amplitude and that the parameters of the NiTi-ST may determine the emergence or disappearance of the CDR. This vibration absorption device can be extended to offer more general vibration control in engineering applications. [ABSTRACT FROM AUTHOR]

In this study, an optimized dynamic vibration absorber (DVA) was applied to improve the sound absorption performance and simultaneously attenuate vibrations and structure-borne noise at multiple frequencies. As the size parameters and eigenfrequencies of a DVA demonstrate a nonlinear relationship, tuning the eigenfrequencies by heuristically modifying the geometric parameters of the DVA is difficult. To avoid this intricate process, geometric parameters were optimized using a gradient method solver to tune the eigenvalues of the DVA to the target frequencies. Post-processing was performed for the sake of manufacturing. To confirm the validity of the performance of the sound absorption and vibration/noise attenuation, impedance tube experiments and impact experiments were conducted using the manufactured DVA. The impedance tube experiment verified that the values of the sound absorption coefficient increased with the application of the DVA. From the impact experiments, it was verified that the values of the frequency response function and sound pressure level decreased with the application of the DVA. The present study validates the notion that optimized DVAs improve the sound absorption performance of structures and simultaneously reduce vibrations and sound pressures at multiple desired frequencies. [ABSTRACT FROM AUTHOR]

The motivation of this study stems from a retaining wall made of waste tires. The wall did not suffer any earthquake or tsunami-induced damage during the 2011 Off the Pacific Coast of Tohoku Earthquake, Japan. This paper deals with a case study on this tire retaining wall. Results from a series of field and laboratory investigations are first described. A numerical simulation is also described in which whole tires were used as protective layers in an embankment. The results show that confining effect of each tire, friction between the tires, ductility, and damping inherent in tires contribute towards the excellent performance of the retaining wall during the earthquake loading. The case study also reveals that it is the isolation mechanism due to the vibration absorption capability of rubber particles in tires, which could protect tire retaining structure during the earthquake. [ABSTRACT FROM AUTHOR]

Additive Manufacturing (AM) method enables to produce products easily, cheaply and quickly with more complex geometry compared to traditional production methods. In this context; Fused Deposition Modeling (FDM) is a widely used for AM method that requires a large number of process parameters. In this study, it is aimed to experimentally investigate the damping capabilities of the metal/polymer composite sleeve bearings printed using FDM. A total of 54 pieces (27 pairs) were printed from composite filaments such as nine pairs for each of PLA, PLA + 20% Bronze, and PLA + 20% Copper metal/polymer with different filling structures (Octogram spiral, Archimedian chords, and 3D Honey comb) and different occupancy rates (10, 30, and 50%), respectively. The experiments were carried out using the shaft-bearing system under the same operating conditions at a rotational speed of 900 revolution per minute (rpm), and vibration data was collected from the rotating shaft with proxy probes. Rotating shaft position is very important to determine journal position in bearing for understanding deterioration in the bearing. Bode and Orbit plots are used to detect the level of deterioration in the bearing. The value of bearing to shaft clearence can vary widely depending on application. Since the bearings were heavily loaded, they were compressed by radial load caused large clearence. The results showed that compressed bearing had significant influence on the stability of rotating shaft system and significant differences in damping capabilities of composite sleeve bearings with different filling structures and occupancy rate. Increasing occupancy rate decreases the vibration amplitude values in copper-reinforced sleeve bearing but increases in bronze-reinforced sleeve bearing. From the microstructure analysis, it has been observed that the vibration absorbation capability is better due to the more homogeneous distribution of the copper reinforced bearings than the bronze reinforced bearings. Also, vibration absorption capability of sleeve bearings with 3D Honeycomb filling structure is increased significantly proportion to the occupancy rate. [ABSTRACT FROM AUTHOR]

A double tuned mass damper (DTMD) for suppressing oscillations of civil structures is proposed in this study. DTMD is a combination of an undamped TMD and a smaller TMD. The impact of parameters on the essential characteristics, as well as the vibration absorption capacity of DTMD, is investigated. Using genetic algorithms (GA), the optimum parameters of DTMD are determined by minimizing the peak dynamic magnification factor of structural responses for a wide range of excitation frequencies. The effectiveness and robustness of DTMD are also compared with those of the optimized TMD having a similar weight as the DTMD. Furthermore, multi-objective optimization designs of DTMD (for both two-objective and three-objective) are also developed here. This study indicates that the DTMD is more effective than a single TMD. If keeping a similar efficiency to that of an optimized TMD, the optimum DTMD has a broader domain for choosing the frequency and damping ratio. In this sense, a DTMD is much more robust than a single TMD. [ABSTRACT FROM AUTHOR]

The strong and complex vibration from a manipulator for anchor drilling will damage the key components of the manipulator and produce noise at the same time. According to its vibration characteristics, a fluid–spring vibration absorption approach with five degrees of freedom (DOFs) is proposed, which has perfect symmetry, and a vibration absorber was designed with a symmetrical structure. Employing the generalization formula of the Bernoulli equation and dynamic equation, a fluid–spring coupling damping coefficient equation was constructed. Vibration transmissibility was used as the evaluation index of vibration absorption performance. The elastic coefficients of the tension spring and torsion spring, the area ratio of circular through-holes to the vibration-absorbing plate, and the radius of circular through-holes were the main independent factors influencing the damping coefficients. An orthogonal experiment with four factors and four levels was designed. Using FLUENT and SIMULATION to implement joint simulations, the distribution law of the flow fields and the damping coefficients of each approach were obtained, and then the best combination of factors was selected. Taking a manipulator used for anchor drilling in Huainan of China as a case study, using the designed fluid–spring vibration absorber, the vibration displacements in the five DOFs were reduced by 68.32%, 49.82%, 52.17%, 49.01%, and 57.09% respectively, indicating a good vibration absorption performance with symmetry about the z → -axis. [ABSTRACT FROM AUTHOR]

Models of hand--arm systems (HAS) are purely mechanical. These models do not include the biological active behaviour of the system, even though it has been known since 1997 that there is a tonic vibration reflex. Since then, several authors have investigated this reflex and related it to grip force, posture and some others features of mechanical vibration power absorption. Other scholars proposed models of HAS that do not include the tonic vibration reflex and its consequences. These models, even partial models, are nonetheless effective in describing many aspects of vibration exposure. This is probably due to the complexity of the HAS, so that the confounding factors overwhelm measurements. [ABSTRACT FROM AUTHOR]

• An energy harvesting dynamic vibration absorber (EHDVA) is proposed for both vibration mitigation and energy harvesting. • The EHDVA with quasi-zero stiffness (QZS) is able to fulfill anti-resonance at an ultra-low frequency. • The QZS EHDVA notably outperforms the linear DVA for vibration attenuation in the ultra-low frequency region. • The peak power of the QZS EHDVA can be increased by 279.17% through design optimization. The dynamic vibration absorber (DVA) can effectively suppress undesirable vibration of a host structure, and the energy harvester is also proven to be a feasible way to collect vibration energy from the host structure. However, it is almost impossible to achieve high-efficiency vibration attenuation and energy harvesting at ultra-low frequency by conventional methods. In this paper, a dual-function quasi-zero-stiffness (QZS) energy harvesting dynamic vibration absorber (EHDVA) is proposed to mitigate vibration and harvest energy simultaneously. The proposed device mainly composed of a QZS absorber and an electromagnetic transducer. The quasi-zero stiffness is realized using a vertical spring connecting with two oblique springs in parallel. The electromagnetic transducer consists of permanent magnets and coils, and any relative motion between the permanent magnets and coils brings flux linkage variation and generate induced voltage. Firstly, the theoretical model of the QZS EHDVA is established and the statics analysis of QZS absorber is carried out. Then, the Harmonic Balance Method (HBM) along with numerical path continuation is applied to solve the electromechanical coupled equations of the QZS EHDVA. Moreover, both numerical and analytical methods are used to evaluate the influence of mechanical and electrical parameters on performances of vibration absorption and energy harvesting. Finally, the H ∞ optimization on system parameters of the QZS EHDVA are conducted with the aid of perturbation method. It indicates that the optimized QZS EHDVA can considerably reduce resonance peaks of the host oscillator at ultra-low frequency and effectively enhance energy harvesting at the same time. [ABSTRACT FROM AUTHOR]

Abstract The Acoustic Black Hole (ABH) is an effective structure for harvesting and dissipating energy from flexural waves. It works by reducing the thickness of the ABH wedge in a power law relationship with m ≥ 2, which rapidly decreases the local phase velocity of flexural waves and leads to an energy convergence effect. However, the vibration performance may differ if the tapered wedge does not meet the requirements of a typical ABH. This article introduces and discusses two types of “pseudo-ABH” wedges: linear-degenerate ABH and step-degenerate ABH. These wedges do not follow the power-law and continuity conditions of typical ABH, respectively. To establish the dynamic models of pseudo-ABH wedges, the lumped-mass transfer matrix method (LTMM) and traveling wave analysis are introduced and validated using analytic solutions of the non-uniform one-dimensional Euler-Bernoulli beam and finite element method. Meanwhile, a good match between the results of the Timoshenko and Euler-Bernoulli beam theory also indicates the correctness of our model. The energy ratio and reflection coefficient are defined to characterize the energy accumulation effect and vibration absorption performance of the pseudo-ABH wedges. The vibration performance of the linear-degenerate ABH is closer to the typical ABH than the step-degenerate ABH. The step-degenerate ABH has more effective energy accumulation and reduction performance for individual frequencies. However, as the number of segments in the step-degenerate ABH increases, its dynamic performance becomes closer to that of the typical ABH. The novelty of this article is to study vibration energy accumulation and absorption characteristics of pseudo acoustic black hole wedges using LTMM model, disclose the differences of linear and step degenerate ABH for their performance, and recommend the step degenerate ABH in place of the typical ABH of a power law thickness relationship. [ABSTRACT FROM AUTHOR]

To improve the reliability and service life of thrust cylindrical roller bearings (TCRBs), the effects of single/compound pit texture on tribological properties and on friction-induced vibration and noise were studied. Laser marking equipment was used to create compound pit texture on a shaft washer. A universal friction and wear test rig was used to measure the friction force, vibration acceleration, and noise signals of TCRBs. The differences between the single/composite pit-textured and non-textured surfaces were studied in terms of the friction, wear, and vibration noise properties. The results revealed that the friction force and wear loss of the single/composite pit-textured surface were markedly lower than those of the non-textured surface. Compared to non-textured surface bearings, the friction force and wear loss for textured surface bearings were reduced by 39.6 % and 59.6 %, respectively, when the diameter, depth, and area density of the pit were 300 µm, 10 µm, and 10 %, respectively. The single/composite pit-textured surface exhibited good potential for vibration absorption and noise suppression. It could effectively interfere with the self-excited vibration of the TCRBs friction pair system, thereby reducing the degree of vibration noise of the TCRBs. [ABSTRACT FROM AUTHOR]

H2O and OH are readily detected in hydrated minerals in CM chondrites via reflectance spectroscopy due to their characteristic vibration absorptions at infrared wavelengths. Previous spectroscopic work on bulk powdered CM chondrites has shown that spectral parameters, like the wavelength position of the "3 μm absorption feature," vary systematically with the extent to which the samples have been aqueously altered. However, it is yet unclear how these spectral features may vary across an intact meteorite chip when measured at spatial scales smaller than that of the individual components of the meteorite. Here, we explore the spatial variability of this spectral feature and others on intact CM2 chips which, unlike powders, retain their petrologic and textural characteristics. We also model the modal mineralogy of the bulk meteorite powders and correlate this with key spectral features, demonstrating that microscope Fourier transform infrared spectroscopic mapping provides a powerful, rapid, and non‐destructive technique for assessing compositional diversity and variations in water–rock interactions in chondritic planetary materials. In all CM2 chondrites studied here, we find that variations in the position, shape, and strength of the 3 μm absorption feature reveal a single chondrite can exhibit as much spectral variation as the entire suite of CM2 chondrites. The observed variations in the position and shape of the 3 μm feature within individual CM2 chondrite chips suggest a range of alteration products (e.g., Mg‐rich to Fe‐rich phyllosilicates) are present and record sub‐mm scale variations in the amount and/or chemistry of the altering fluids. The samples having experienced the most progressive aqueous alteration show the least amount of variability in features like the 3 μm absorption band minimum position, whereas the least altered samples exhibit the most variability. We also find that the bulk spectral signatures in the least altered samples appear to be biased toward the spectral signatures of clasts versus matrix. By extension, asteroid reflectance spectra exhibiting 3 μm absorption features consistent with those measured here may be interpreted in a similar framework in which the spectrum of what may appear to be the least altered asteroids represents an average that belies the true diversity of mineralogy and chemistry of the body. [ABSTRACT FROM AUTHOR]

One of the most effective approaches for seismic protection of structural systems is isolation. The majority of existing seismic protection systems are related to horizontal ground motion and only few focus on vertical seismic components, as this would require vertical flexibility, a feature conflicting with the need for sufficient support of the isolated structure. In order to overcome this difficulty, a novel vertical Stiff dynamic absorber (SDA) is proposed that combines a Quasi-Zero Stiffness design including negative stiffness elements, an enhanced Tuned Mass Damper, and Inerter elements. The present work deals with the optimization problem for the determination of the various design parameters of the proposed configuration, aiming at minimizing the vertical accelerations induced on the structure while keeping the displacement within reasonable limits. The values of the optimized design parameters depend only on the characteristics of the isolated structure irrespectively of the excitation input. This feature differentiates the proposed SDA from similar versions found in the literature and renders the design applicable for use across a wide range of vertical vibration control applications. The proposed configuration is designed to achieve great acceleration isolation without compromising the weight-bearing capacity of the structure. This is realized through the appropriate determination of the static and dynamic stiffnesses via a novel calculation approach that is based on the initial static equilibrium point. The role of various design factors is investigated based on time-history responses of a reference structure to artificial accelerograms matching EC8 criteria, and the effect of the optimized SDA is evaluated on real earthquake records, confirming its capacity to greatly reduce the response to structure accelerations. The selection of the design parameters is based on engineering criteria and an indicative implementation of the design elements is included, demonstrating the feasibility of the proposed configuration. [ABSTRACT FROM AUTHOR]

We theoretically, numerically, and experimentally study a lightweight metastructure that can simultaneously reduce vibration and noise in a broad low-frequency range. We introduce spiral slits and micro-perforations in the panel and core plate of a face-centered cubic sandwich structure, respectively. A bottom-up acoustic impedance theory is developed to describe the impedance of a single unit cell. Broadband low-frequency sound absorption is achieved for a 3 × 3 supercell via reinforcement learning optimization. The resonant coupling of the upper spiral panel and the lower panel of the unit can form a wide hybridized bandgap for flexural waves, which is further validated for vibration isolation with a one-dimensional supercell. The proposed multifunctional metastructure provides a new route to design lightweight load-bearing structures with noise and vibration reduction performance for potential applications such as aerospace engineering and transportation vehicles, among others. [ABSTRACT FROM AUTHOR]

Nowadays, the inerter device has become one of most popular mechanical devices in the vibration absorption field for both stationary and non-stationary mechanical structures. One of the problems commonly reported in the literature is the force transmission control in the foundations that support the machines, which is generally addressed by using either isolators or classic dynamic vibration absorbers (DVAs). However, the mechanical energy dissipation capability of these two solutions is still limited. This work focuses on improving the control performance for the conventional absorber using the inerter's inertial mass amplification and negative stiffness effects. In order to fairly evaluate the control performance of the DVA based on grounded inerter, the ℋ∞ and ℋ2 optimization criteria are proposed. When the dimensionless frequency response function (FRF) of the transmissibility is minimized at the resonant peaks, the ℋ∞ criterion reveals an improvement of 29.74% in mitigating harmonic vibration. Finally, the total vibration energy transmitted to the foundation is minimized via ℋ2 criterion that provides an improvement of 33.03%. [ABSTRACT FROM AUTHOR]

The nonlinear energy sink (NES) is an effective method to weaken or eliminate the line spectra feature of ship machinery equipment. However, due to the strong nonlinearity of the NES, there are multistable attractors in the NES vibration absorption system. Moreover, when the excitation characteristics or working conditions of the mechanical equipment change, the NES may migrate from the small-amplitude motion state to the large-amplitude motion state, resulting in a high-amplitude solitary branch response and thereby lowering its vibration absorption efficiency. In this study, the small-amplitude control of the NES nonlinear vibration absorption system has been studied by using the open-loop-plus-nonlinear-closed-loop (OLPNCL) method. First, the dynamic equation of the NES nonlinear vibration-absorbing system was formulated, and its global behavior was analyzed. The regulations of global features and coexisting attractors were found out. Second, the migration between different attractors was carried out under the OLPNCL control, which can ensure that the system always works at the lowest line spectrum intensity and the best overall vibration absorption performance. Finally, the simulation results verify the feasibility and effectiveness of the OLPNCL method and achieve effective vibration absorption in the low-frequency range and line spectrum control under variable operating conditions. [ABSTRACT FROM AUTHOR]

Power equipment shows obvious low frequency line spectrum noise characteristics due to the power frequency. The effective noise control of the power equipment can be achieved by installing dynamic vibration absorbers (DVAs) on the structure surface of electrical equipment. However, if DVAs are not installed properly, considering the cases that they are installed at the vibration mode node position, the low radiation vibration mode and the redistribution of the integrate vibration power, the vibration and noise absorbing performances of DVAs may degrade. In order to achieve efficient vibration absorption and noise reduction on the power equipment, this paper proposes a low-frequency noise reduction technology for power equipment based on DVAs. The position optimization of the DAVs using in the power equipment is studied for the first time. Aimed at the single frequency radiated sound power of equipment, the integrate radiated sound power of the equipment is minimized through adjusting the position parameters of DVAs. A numerical case is studied to verify the effectiveness of the proposed DVAs position optimization. The results show that the noise control effect of the power equipment with the optimized DVAs is significantly improved. The method proposed in this paper solves the noise problem of the power equipment, which provides reference for power noise control. [ABSTRACT FROM AUTHOR]

In this work, an elastic metamaterial (EMM) structure with multiple resonant modes that can generate bandgaps is proposed. Through proper geometrical adjustments, the resonant frequency and sequence of the resonant modes can be tuned to form continuous bandgaps. This is in contrast to commonly used elastic metamaterial configurations with only one primary local resonance mode for bandgap opening, resulting in relatively narrow bandgap widths. The effect of geometrical parameters on the bandgap property is investigated via numerical simulation. Numerical results verify the accuracy of dispersion relation prediction on the bandgap location and width. A bandgap with maximum width of 100.2 Hz in the low frequency range (< 300 Hz) is found numerically. Prototype samples of the proposed EMM are fabricated, and experimental tests have been conducted. Testing results for all prototypes validate the formation of an even larger bandgap than numerically predicted. The largest bandgap measured is about 256 Hz. The damping allows the bandgaps to merge and form a broad continuous one. The utilization of asymmetric structure design is proposed in this present work to enlarge the bandgap width through enhancing the interaction between the relevant resonant modes and the incident wave. With a proper geometrical parameter selection, the bandgap associated with the torsional resonant mode can be enlarged by about 64.4%. This work confirms that the breaking of self-balance condition in the symmetric EMM structure can enhance the torsional mode-related bandgap performance. It thus provides a new design pathway for the bandgap enlargement for elastic metamaterials for applications in structural vibration control. [ABSTRACT FROM AUTHOR]

In the field of dynamics and control, some typical vibration devices, including grounded stiffness, inerter and amplifying mechanism, have good vibration isolation and reduction effects, especially in dynamic vibration absorber (DVA). However, most of the current research studies only focus on the performance of a single device on the system, and those DVAs are gradually becoming difficult to meet the growth of performance demand for vibration control. On the basis of Voigt dynamic vibration absorber, a novel dynamic vibration absorber model based on the combined structure of grounded stiffness, inerter, and amplifying mechanism is presented, and the analytical solution of the optimal design formula is derived. First, the motion differential equation of the system is established, and the normalized amplitude amplification factor of the displacement is calculated. It is found that the system has three fixed points unrelated to the damping ratio. The optimal frequency ratio is obtained based on the fixed-point theory. In order to ensure the stability of the system, it is found that inappropriate inerter coefficient will cause the system instable when screening optimal grounded stiffness ratio. Accordingly, the best working range of inerter is determined. Finally, optimal grounded stiffness ratio and approximate optimal damping ratio are also obtained. The influence of inerter coefficient and magnification ratio on the response of the primary system is analyzed. The correctness of the derived analytical solution is verified by numerical simulation. Compared with other dynamic vibration absorbers, it is verified that presented model has superior vibration absorption performance and provides a theoretical basis for the design of a new type of dynamic vibration absorbers. [ABSTRACT FROM AUTHOR]

The belt-drive control enables the mechanical system to gain the advantages of lightweight, vibration absorption, and high torque, while it brings strong nonlinear disturbances due to friction, backlash, and flexibility. Therefore an improved disturbance observer (DOB) control method based on the dual-rate loop structure is proposed in this article to suppress these disturbances. Only a linear low-frequency device model is required, which indicates that this method avoids the dependence on accurate identification of the nonlinear uncertain systems. The rate information on the motor-side is replaced with the input signal of inner loop due to the high bandwidth of inner motor loop, which greatly simplifies the design of the control system. In the case of insufficient system bandwidth, the proposed method integrates the favorable information of the load-side and the motor-side under the DOB framework. And the speed-commutation spikes and chatters resulting from disturbances on the flexible transmission chain can be more effectively suppressed by the proposed control structure compared with the conventional methods. [ABSTRACT FROM AUTHOR]

• The synchronization conditions and stability criterion of the dynamic vibration absorption system are derived. • To obtain large excitation force, a new elastic coupling three-exciter vibration system is proposed. • The influence of structural parameters on the dynamic characteristics is discussed by numerical analysis. • The simulation and experiment can verify the correctness of theoretical analysis. • Vibration absorption effect and double-frequency synchronization ability are ideal. Vibrating screen is the pivotal equipment to separate drilling fluid and cuttings during oil exploitation. However, some inherent defects such as low screening efficiency, vibration fatigue and structural failure are observed in the most of conventional vibrating screens with single screen box and same-frequency actuation. For the above-mentioned problems, a newly dynamic vibration absorption device driven by multiple-rotor and double-frequency is designed. To explore the dynamic characteristics of the vibrating device, the vibration isolation performance and the synchronization mechanism are studied in this paper. Firstly, the dynamic equations of the system are established by Lagrangian method. Subsequently, on the basis of averaging method, the synchronization condition and the stability criterion are theoretically deduced. Then, the influence of structure parameters on synchronization and vibration isolation are numerically discussed. Later, the correctness of the theoretical research results is verified by simulation and experiment. Finally, the research results indicate that the synchronization of the vibrating system is mostly determined by mass ratio of the eccentric rotors and mounting position of the motors. Meanwhile, the research results will provide theoretical direction for the design of new vibrating screen. [ABSTRACT FROM AUTHOR]

The paper aims to identify the situations in which a complex elastic system, which is subject to mechanical vibrations, can act as a dynamic absorber of vibrations for certain frequencies. The conditions that the system must fulfill in order to achieve this goal are determined and then a calculation example is presented. The method is interesting because it allows to avoid attaching an absorber specially built for this, a situation that complicates the project and increases manufacturing costs. [ABSTRACT FROM AUTHOR]

An adaptive dynamic vibration absorber (ADVA) is designed for low-frequency vibration suppression. The leaf springs are applied as the tuning stiffness elements. The principle of variable stiffness is analyzed to obtain the effective range of the first natural frequency variation. A classic simply supported manipulator is selected as the controlled system. The coupled dynamic model of the manipulator-ADVA system is built to obtain the maximum damping efficiency and the vibration absorption capacity of the designed ADVA. An experimental platform is set up to verify the theoretical results. It is revealed that the ADVA can adjust the first natural frequency on a large scale by changing the curvature of the leaf springs. The amplitude of the manipulator is reduced obviously with the installation of the designed ADVA. Finally, based on the short-time Fourier transformation (STFT), a stepwise optimization algorithm is proposed to achieve a quick tuning of the natural frequency of the ADVA so that it can always coincide with the frequency of the prime structure. Through the above steps, the intelligent frequency tuning of the ADVA is realized with high vibration absorption performance in a wide frequency range. [ABSTRACT FROM AUTHOR]

Low glycemic index (GI) food can be very necessary to alleviate the ever-increasing prevalence of diabetes, particularly for the high-quality living standards and health care services. Among them, the starch-lipid complexes can serve as a new type of resistant starch for excellent anti-digestive properties in recent years. High amylose corn starch (HACS) is considered an ideal raw material for the preparation of starch-lipid complexes, due mainly to the high amylose content. Meantime, the twin-screw extrusion has been successfully applied to fabricate the starch-lipid complexes. It is a high demand to enhance the preparation efficiency of starch-lipid complexes for scale production in anti-digestive food. The purpose of this study was to optimize the extrusion process for better structure and physicochemical properties of HACS-lipid complexes using single-factor and orthogonal experiments. Among them, the complex index (CI) was selected as the indicator. The high-amylose corn starch and flax oil were used as the material to prepare the complexes using twin-screw extrusion. The process parameters were adjusted separately, including the mass ratio, feed moisture, barrel temperature, and screw speed. The extruded complex was dried at 40 ℃ in an oven for 10 h, and then ground and passed through an 80-mesh sieve. The highest CI reached 85.63%, when the optimal parameters were 0.24 of flax oil-to-starch ratio, 40% of feed moisture, 125 °C of barrel temperature, and 150 r/min of screw speed. Fourier transform infrared spectroscopy (FTIR) pattern found the new peaks at 2 850 and 1 743 cm-1 in the extruded starch-lipid complex, corresponding to the C-H and C=O vibration absorption peak of lipid molecules in the complex. Moreover, the C=O vibration absorption peak of the extruded complex was shifted to the lower wavenumber, compared with the control. It infers that the lipid molecules combined with the starch were at the actions of shearing, friction force, and heat moisture during extrusion. Specifically, the extrusion first broke the hydrogen bonds of starch molecules to expose the hydrophobic helical cavity, where the lipid molecules were entered under hydrophobic interaction. The morphologies showed that the complexation induced the stacking and aggregation of starch granules. The V-type crystalline X-ray diffraction (XRD) pattern was found in the extruded complex, indicating the feasible preparation of the complexes after twin-screw extrusion. Compared with the control and HACS, there was a higher gelatinization enthalpy in the extruded complex, indicating that more energy was required to gelatinize the complex. By contrast, the extruded complex demonstrated a lower apparent viscosity, storage modulus, and loss modulus, compared with the control. Additionally, there was the highest total amount of slowly digestible starch (SDS) and resistant starch (RS) in the extruded complex among all samples, indicating the better anti-digestible properties of the complex. It can be concluded that the extrusion can promote the effective complexation between the starch and fax oil, thus altering the structure and physicochemical properties of corn starch. Therefore, the starch-lipid complex prepared by twin-screw extrusion can be expected to serve as a potential material for low GI food production. [ABSTRACT FROM AUTHOR]

A self-powered electromagnetic vibration suppression and absorption system integrated with a magnetorheological damper and a linear motor is designed to attenuate the negative effect of vertical vibration caused by the increased unsprung mass for in-wheel motor electric vehicles in this article. The magnetorheological damper is used as a suspension damper to suppress body vibration, and linear motor is used as a dynamic vibration absorber, namely, linear electromagnetic dynamic vibration absorber, to absorb tire vibration, and regenerates the vibration power to drive the magnetorheological damper, realizing self-power. Based on power flow theory, the power transfer mechanism of the vertical vibration for in-wheel motor electric vehicles and the regeneration potential are analyzed. The negative effect on the dynamic performance of in-wheel motor electric vehicles is analyzed through the root mean square of dynamic responses. Moreover, the specific structure scheme of the self-powered electromagnetic vibration suppression and absorption system is provided. The influence of system mass, stiffness, and damping of the linear electromagnetic dynamic vibration absorber on the dynamic performance is analyzed, and these parameters are optimized by particle swarm optimization. Simulation results show that in comparison with a passive damper, the self-powered electromagnetic vibration suppression and absorption system can reduce the body acceleration by 17.05%, which is better than the magnetorheological damper (10.08%). The self-powered electromagnetic vibration suppression and absorption system increases the tire dynamic load by 5.62%, but it is 8.68% less than the magnetorheological damper. Additionally, the regenerated power can offset the consumed power adequately to realize self-power. Finally, a bench test is conducted to verify the effectiveness and feasibility of the self-powered electromagnetic vibration suppression and absorption system. [ABSTRACT FROM AUTHOR]

Tests for measuring the vibration characteristics of a typical fuselage panel of a regional aircraft, as well as the board, flap, and wing structures of a real aircraft with various vibration damping sets, have been carried out in reverberation chambers and on a full-scale testbench. Under the conditions of acoustic excitation for a model panel and real aircraft structures, the efficiency has been determined for the following vibration reducing means: the change of the boundary conditions and stiffness of frames, the lining of a structure with single-sided vibration-damping sandwiches and sheet vibration-absorbing materials VTP-1V and SKLG-6020M, and the use of stringer and frame simulators, including their combinations with dual-sided vibration damping sandwiches. It is shown that a significant decrease in structural vibrations can be attained within a broad range of frequencies by using a combination of different methods. At low frequencies, an effective tool is the conversion of long-wave frame vibration forms into shorter-wave ones. In the region of medium frequencies, structural vibrations can be efficiently reduced by single-sided sandwiches, as well as stringer simulators together with dual-sided sandwiches. In the region of high frequencies, the most effective means is the lining of a structure with sheet vibration-absorbing coatings. [ABSTRACT FROM AUTHOR]

Shock and vibration generated during transport can lead to overload failure and fatigue fracture in museum objects. Damage can be prevented using transport packing providing both adequate shock absorption and vibration isolation. This research demonstrated that standardized packing with enhanced vibration mitigation is achievable for three-dimensional objects in a busy museum environment. Based on state-of-the art predictive modelling, extensive engineering and collection care expertise, a calculator tool was developed that allows users to create packing with improved vibration isolation by using the overall dimensions and weight of an object. This research highlighted that effective vibration mitigation can only be designed in a concerted cross-disciplinary effort by engineers and collection care professionals. [ABSTRACT FROM AUTHOR]

In this paper, the gradient anechoic coating whose density changes exponentially along direction of thickness is investigated. A numerical model is established by finite element method (FEM) to analyze the underwater sound absorption performance under different density distribution. The calculation results show that the exponential anechoic coating has better sound absorption performance compared with the homogeneous medium and linear anechoic coating. In addition, a discrete layered method is proposed to achieve gradient characteristics. In order to change the equivalent density of each layer, periodically distributed semi-cylindrical steel scatterers with different diameters are embedded in each layer. Therefore, the density function of the whole coating changes in exponential gradient with stepped function. Based on the sound absorption mechanism of multiple scattering and waveform conversion, the sound absorption is improved in low-frequency band from 0 Hz to 1000 Hz. The exponential gradient anechoic coating has potential applications in underwater sound absorption and vibration control. [ABSTRACT FROM AUTHOR]

The new staggered story isolated structure is a new type of seismic isolated structure developed from base isolated structure and inter-story isolated structure. In order to explore the seismic response of the new staggered story isolated structure considering the soil-structure interaction (SSI), the model of a new staggered story isolated structure considering SSI effect is established to analyze the nonlinear dynamic time-history response under rare earthquakes, and the comparison between hard soil and soft soil was carried out. Results show that the stiffness of the new staggered story isolated structure reduced, the modal period extended and the seismic response reduced by considering the SSI effect, the softer the site soil, the more obvious those changes are. Meanwhile, the shear force and the damage of the core tube decreases, while the shear force and the damage of the frame increases, the shear force transfers from the core tube to the frame. Additionally, the energy absorption of the seismic isolated bearings at the frame reduced, the energy absorption of the seismic isolated bearings at the core tube increased, the softer the site soil, the more obvious the trend is. [ABSTRACT FROM AUTHOR]

Radiant heat dissipation has emerged as a critical technique for effective thermal management, offering energy efficiency, cost-effectiveness, and adaptability to various shapes while promoting environmental sustainability. However, the intricate relationship between material structures and emissivity remains inadequately understood. This study primarily utilizes a straightforward and economical solvothermal method to regulate the synthesis of Fe 3 O 4 ferrite, exploring its structural relationship with infrared radiation performance. By adjusting the solvent ratio of ethylene glycol and diethylene glycol in the solvothermal system, we successfully synthesized uniformly dispersed Fe 3 O 4 nanospheres ranging from 10 to 800 nm. Notably, our research revealed a positive correlation between infrared emissivity and the particle size. Submicron hollow spheres with a size of 800 nm exhibit an exceptionally high emissivity of 0.992 within the 8–13 μm wavelength range. Morphological and size variations induced alterations in lattice strain, oxygen vacancies, and phonon lifetimes, which consequently influencing the lattice vibration absorption and infrared emissivity. Moreover, the device surface with a composite coating formed by combining 15 wt% Fe 3 O 4 particles with organic matter, achieves a temperature difference of 17.6 °C under a 4 W input power condition compared to blank device. This finding contributes to further revealing the process of material radiative heat dissipation, driving the application of high-emissivity materials for heat dissipation in high-power electronic devices. • Modifying spherical Fe 3 O 4 size and microstructure can regulate infrared emissivity. • Lattice distortion and oxygen vacancy defects boost infrared emissivity. • Enhanced optical phonon scattering correlates with higher infrared emissivity. • A 15 wt% Fe 3 O 4 @PDMS coating maintained a steady-state temperature of 17.6 °C. [ABSTRACT FROM AUTHOR]