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Pathogens are ubiquitous in ecosystems and play a key role in affecting host community structure. In grasslands, large grazing animals such as cattle and sheep have been shown to affect foliar fungal pathogens. However, theory and empirical studies have come to conflicting conclusions because grazers can directly and indirectly impact pathogens through a wide variety of mechanisms and various grazers may impact pathogens in different ways. A better understanding of the mechanisms by which grazers impact pathogens is important for a fundamental understanding of herbivore pathogen interactions and also to optimise grazing managements to reduce pathogen outbreaks.Here, we investigate multiple mechanisms by which livestock grazing impacts foliar fungal pathogens in grasslands. We integrate a large‐scale grazing experiment, with a removal experiment manipulating plant density and litter biomass, to identify direct and indirect effects of two herbivores on pathogens with different life histories (biotrophs and necrotrophs), in a temperate grassland in northeast China.We found that grazing by cattle and sheep had contrasting impacts: cattle grazing significantly reduced pathogen load, of both biotrophs and necrotrophs, whereas sheep grazing increased biotrophic pathogen load, but did not affect the necrotrophs. The grazing effects were mostly indirect and mediated by different impacts of the herbivores on plant community structure. Cattle grazing reduced pathogen load because it reduced the abundance of susceptible, fast‐growing plants, and the overall density of plants, while sheep grazing increased pathogen infection because it reduced the abundance of resistant plant species. Plant diversity also reduced pathogen infection but these effects were independent of the herbivores.Our results show that different herbivores can have contrasting impacts on pathogen infection through contrasting impacts on host community competence. This suggests the importance of considering multiple mechanisms simultaneously to evaluate the impact of herbivores on host‐pathogen interactions. Read the free Plain Language Summary for this article on the Journal blog. [ABSTRACT FROM AUTHOR]

• Developing a nondestructive approach for the critical pressure of functionally graded combined shells with hydrostatic pressure. • Equivalent model of hydrostatic pressure for functionally graded combined shells is proposed. • The validity of the developed computational model is verified by numerical examples. • The effects of power-law exponents, geometric parameters, boundary conditions on critical pressure are discussed. This paper describes a unified nondestructive semi-analytical formulation for the critical pressure of underwater functionally graded combined shells subjected to external hydrostatic pressure. The structural model of combined shells is constructed from the first-order shear deformation theory, Voigt mixing law, and virtual spring technology. The admissible displacement functions are uniformly expressed with Legendre polynomials along the generatrix direction and Fourier series along the circumferential direction. The Kirchhoff-Helmholtz boundary integral equation is discretized by using the Legendre-Gauss spectral boundary element method, and the external acoustic field model is derived by expanding the Green's function, sound pressure, and displacement of combined shells with one-dimensional Fourier transformation. The linear elastic material theory is applied to deduce the work done by the hydrostatic pressure. The key technology to predict the critical pressure is to create an accurate equivalent model of the hydrostatic pressure. Through solving the final coupled governing equation, the critical pressure is obtained from the linear relationship between the hydrostatic pressure and the square of natural frequency. The convergence and correctness are verified by comparison with the results from published papers and numerical methods. The effects of different hydrostatic pressures, power-law exponents, geometric parameters, and boundary conditions on the critical pressure are investigated in several examples. Computed results can provide security guidance for the nondestructive prediction of underwater functionally graded combined shells at the beginning of engineering application design. [ABSTRACT FROM AUTHOR]

Summary: Parasites can catalyze or inhibit interactions between their hosts and other species, but the ecosystem‐level effects of such interaction modifications are poorly understood.We conducted a large‐scale field experiment in temperate grasslands of China to understand how foliar fungal pathogens influenced top‐down effects of cattle on plant diversity and productivity.When foliar pathogens were suppressed, cattle grazing strongly reduced biomass of the dominant grass, Leymus chinensis, generating competitive release that significantly increased community‐level species richness and evenness. In the absence of grazing, pathogen attack on L. chinensis had no measurable effect on host biomass. However, pathogens disrupted top‐down effects of herbivory by inhibiting grazing effects on plant biomass and species richness. Mechanistically, fungal pathogens were linked to increased alkaloid and reduced nitrogen levels in leaf tissue, which appeared to deter cattle grazing on L. chinensis.In conclusion, foliar pathogens can suppress top‐down effects of large herbivores on grassland community composition and ecosystem function by modifying the strength of their host's interactions with dominant consumers. Parasites may act as modulators of ecosystem function when their direct effects on host abundance are overshadowed by powerful influences on host traits that modify their interactions with competitors, herbivores, or predators. [ABSTRACT FROM AUTHOR]

Modulation recognition is the indispensable part of signal interception analysis, which has always been the research hotspot in the field of radio communication. With the increasing complexity of the electromagnetic spectrum environment, interference in signal propagation becomes more and more serious. This paper proposes a modulation recognition scheme based on multimodal feature fusion, which attempts to improve the performance of modulation recognition under different channels. Firstly, different time- and frequency-domain features are extracted as the network input in the signal preprocessing stage. The residual shrinkage building unit with channel-wise thresholds (RSBU-CW) was used to construct deep convolutional neural networks to extract spatial features, which interact with time features extracted by LSTM in pairs to increase the diversity of the features. Finally, the PNN model was adapted to make the features extracted from the network cross-fused to enhance the complementarity between features. The simulation results indicated that the proposed scheme has better recognition performance than the existing feature fusion schemes, and it can also achieve good recognition performance in multipath fading channels. The test results of the public dataset, RadioML2018.01A, showed that recognition accuracy exceeds 95% when the signal-to-noise ratio (SNR) reaches 8dB. [ABSTRACT FROM AUTHOR]

This study presents nonlinear vibration isolators with nonlinear elements created by the geometric nonlinearity of a linkage mechanism with embedded linear springs and investigates their dynamic behaviour and performance. Applications of the proposed isolator to single degree-of-freedom (DOF) systems subjected to force and base-motion excitations and to a two-DOF system with a flexible foundation are considered. The steady-state responses of systems with such isolators are obtained using the harmonic balance (HB) method and a numerical time-marching method. Force and displacement transmissibilities as well as time-averaged energy flow of the nonlinear isolator are employed as indices for performance evaluations. It is shown that the use of the proposed nonlinear element can enlarge the frequency range of effective isolation. Substantial reductions can be found in the peak values of frequency response, displacement transmissibility and kinetic energy of the SDOF nonlinear isolation systems. The peaks in the curves of energy transmission and force transmission are shifted to low frequencies with reduced peak values, beneficial to the suppression of vibration transmission to the flexible base. [ABSTRACT FROM AUTHOR]

Based on the principle of energy variation, an improved Fourier series is introduced as an allowable displacement function. This paper constructs a calculation model that can study the in-plane and out-of-plane free and forced vibrations of curved beam structures under different boundary conditions. Firstly, based on the generalized shell theory, considering the shear and inertial effects of curved beam structures, as well as the coupling effects of displacement components, the kinetic energy and strain potential energy of the curved beam are obtained. Subsequently, an artificial spring system is introduced to satisfy the constraint condition of the displacement at the boundary of the curved beam, obtain its elastic potential energy, and add it to the system energy functional. Any concentrated mass point or concentrated external load can also be added to the energy function of the entire system with a corresponding energy term. In various situations including classical boundary conditions, the accuracy and efficiency of the method in this paper are proved by comparing with the calculation results of FEM. Besides, by accurately calculating the vibration characteristics of common engineering structures like slow curvature (whirl line), the wide application prospects of this method are shown. [ABSTRACT FROM AUTHOR]

Acoustic black hole (ABH) with the power-law profile has the advantages of strong designability and vibration suppression. This study provides a novel virtual spring energy method (VEM) to solve the vibration characteristics of a plate embedded or attached with acoustic black hole. Firstly, the virtual springs in this study can deal with boundary conditions, continuity conditions, and periodic conditions. After solving the kinetic and potential energy of a plate cell embedded with acoustic black hole, the periodic structure's kinetic and potential energy need not be calculated repeatedly. The method is verified by the finite element method. Secondly, to overcome the stiffness reduction owing to the varying thickness of ABH in the primary bearing structure, a composite ABH structure called "Plate–ABH" is proposed, in which a damping layer is designed with an ABH profile and attached to the primary plate structure. The two layers connect each other through the virtual springs. The vibration characteristics of the composite ABH plate are given by employing the VEM. The composite ABH structure shows strong damping ability and lighter weight compared with a plate attached with the uniform thickness damping layer. Plate–ABH can be effectively used in the engineering of vibration reduction. [ABSTRACT FROM AUTHOR]

In practical applications, communication emitters are often carried by low orbit satellites aircraft, ships, and other moving carriers. Doppler phenomenon usually exists due to the relative motion between the emitter and the receiver, which seriously affects the identification performance. Given this situation, a method based on the signal vector decomposition and the multi‐feature fusion is proposed. By normalizing and demodulating the target signal, the signal vector diagram is decomposed into four parts. We present a multi‐feature fusion model with varying features extracted from each diagram by a deep learning network. Experimental results show that the proposed method is effective in the presence of Doppler effect. [ABSTRACT FROM AUTHOR]

Herein, the microporous structure and gas transport property of a new family of polyimides (PIs) containing bulky tetra- o -isopropyl and naphthalene groups prepared via a microwave-assisted polymerization process are reported. The polyimides were prepared from a naphthalene and isopropyl containing diamine, i.e., 4,4'-(naphthalen-1-ylmethylene)bis(2,6-diisopropylaniline)) (i.e., BAN-3) obtained via a one-step electrophilic substitution reaction, reacting with three commercial dianhydrides. Analysis of fractional free volume (FFV) in conjunction with positron annihilation lifetime spectroscopy (PALS) showed that the resultant BAN-3 based PIs had high FFV values of over 0.19 featuring a bimodal size distribution of microcavities with average diameters in the range of 8.0–9.0 Å and 5.6–6.3 Å, respectively. Wide angle X-ray diffraction (WXRD) further confirmed that the introduction of naphthalene and tetra- o -isopropyl groups effectively enhanced polymeric backbone rigidity and disrupted chain packing, leading to high gas permeabilities in all three PI films. For example, the PI-3F film had high H 2 and CO 2 permeability values of 722 and 849 barrer, respectively while maintaining comparable selectivities for H 2 /CH 4 and CO 2 /CH 4 gas pairs with other reported PIs of the same dianhydride. In addition, the PI-3B film displayed excellent gas separation performance for O 2 /N 2 gas pair approaching the 2008 Robeson upper bound. Image 1 • Robust and highly soluble polyimides containing isopropyl and naphthalene units were readily prepared. • The polyimides had high FFV values featuring a bimodal size distribution of microcavities. • The polyimides showed excellent gas selectivity for O2/N2, approaching the 2008 Robeson upper bound. [ABSTRACT FROM AUTHOR]

BACKGROUND: The use of emulsion gels to protect and deliver probiotics has become an important topic in the food industry. This study used transglutaminase (TGase) to regulate ovalbumin (OVA) to prepare a novel emulsion gel. The effects of OVA concentration and the addition of TGase on the microstructure, rheological properties, water‐holding capacity, and stability of the emulsion gels were investigated. RESULTS: With the addition of TGase and the increasing OVA, the particle size of the emulsion gels decreased significantly (P < 0.05). The gels with TGase exhibited greater water holding, hardness, and chewiness to some extent by forming a more uniform and stable system. After simulated digestion, the survival rate of Bifidobacterium lactis embedded in OVA emulsion gels improved significantly in comparison with the oil–water mixture as a result of the protective effect of the emulsion gel encapsulation. CONCLUSION: By increasing the OVA content and adding TGase, the rheological characteristics, stability, and encapsulation capability of the OVA emulsion gel could be enhanced, providing a theoretical basis for the use of emulsion gels to construct probiotic delivery systems. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Glioblastoma (GBM) is the most common malignant tumor of the central nervous system. Vasculogenic mimicry (VM) is a hematological system composed of tumor cells that exert blood perfusion without relying on vascular endothelial cells. The current poor results of anti-vascular therapy for clinical GBM are associated with the presence of VM; therefore, it is important to investigate VM formation in GBM. Our results demonstrate that STK24P1 encodes P1-121aa with a kinase structural domain, and in vitro kinase assays demonstrated that P1-121aa mediates modification of ELF2 phosphorylation. ChIP and dual luciferase reporter gene assays demonstrated that the transcription factor ELF2 binds to VE-cadherin and the VEGFR2 promoter region, thereby promoting VM formation in glioma cells. P1-121aa, encoded by the pseudogene STK24P1, phosphorylates ELF2 at S107, increasing the stability of the ELF2 protein. ELF2 promotes VEGFR2 and VE-cadherin expression at the transcriptional level, which in turn promotes VM in GBM. This study demonstrates the important roles of STK24P1, P1-121aa, and ELF2 in regulating VM in GBM, which could provide potential targets for GBM treatment. [Display omitted] • STK24P1, P1-121aa, and ELF2 were highly expressed in glioma tissues and cells. • Knockdown of STK24P1, P1-121aa, and ELF2 significantly inhibited the VM of GBM. • P1-121aa, encoded by the pseudogene STK24P1. • P1-121aa phosphorylated ELF2 at S107, thereby increasing ELF2 stability. • ELF2 promotes the expression of VEGFR2 and VE-cadherin at the transcriptional level. [ABSTRACT FROM AUTHOR]

Highlights • Liquid temperature and vapor concentration of sprays were studied using LIEF. • Effects of injection parameters on spray evaporation and heat transfer were studied. • The superheated region of flash-boiling spray was a quasi-steady state. • Evaporation of flash-boiling spray was enhanced significantly by decreasing P a /P s. • Heat transfer scheme was studied based on experimental observations. Abstract In order to improve engine thermal efficiency with reduced emissions, substantial studies have been carried out to improve the atomization and evaporation of fuel sprays, as well as fuel-air mixing in the engine cylinder. It has been found that flash-boiling spray is an effective way to achieve these goals. To further understand the evaporation characteristics and hear transfer phenomena between flash-boiling sprays and ambient gas, liquid temperature and vapor concentration of flash-boiling spray were measured quantitatively using laser induced exciplex fluorescence (LIEF) technique. The effects of fuel temperature, ambient pressure and superheated index (P a /P s) on the evaporation characteristics and heat transfer of fuel spray were investigated. The experimental results demonstrate that compared with non-flash-boiling spray, the rapid evaporation of flash-boiling spray leads to a higher vapor concentration along the center line. Meanwhile, the remarkable amount of energy absorbed from liquid phase of flash-boiling spray results in a faster liquid temperature decrease along the center line. When hot fuel is injected into cold environment, increasing fuel temperature leads to an increase of heat transfer from fuel spray to ambient gas because of the higher temperature difference between them. On the other hand, increasing ambient pressure decreases the evaporation rate of fuel spray due to the higher P a /P s. As such, the energy absorbed for fuel evaporation from liquid phase of spray is decreased, the heat transfer from fuel spray to ambient gas is increased. [ABSTRACT FROM AUTHOR]

Here, we develope a kind of biobased transparent polyimides (PIs) with excellent solubility and mechanical properties by using myo-inositol derived diamines. Two biobased diamines M1 and M2 were synthesized through a protection reaction of –OH units of myo-inositol followed by the substitution and subsequent reduction reactions. Myo-inositol based PIs were prepared via the microwave-assisted polymerization of biobased diamines and commercial dianhydrides. These PIs were soluble in various common solvents even in CH 2 Cl 2 and acetone at room temperature. The biobased PIs also showed good optical transparency with T 450nm values of over 82%. Moreover, all the PI films possessed outstanding mechanical properties with tensile modulus of over 3.5 GPa, which was higher than that of most of petroleum-based PIs. In addition, the PI films containing –OH units were obtained via a simple deprotection reaction of myo-inositol based PIs. [ABSTRACT FROM AUTHOR]

The sound-structure coupling problem of a cylindrical shell submerged in a quarter water domain is studied. A semi-analytical method based on the double wave reflection method and the Graf's addition theorem is proposed to solve the vibration and acoustic radiation of an infinite cylindrical shell excited by an axially uniform harmonic line force, in which the acoustic boundary conditions consist of a free surface and a vertical rigid surface. The influences of the complex acoustic boundary conditions on the vibration and acoustic radiation of the cylindrical shell are discussed. It is found that the complex acoustic boundary has crucial influence on the vibration of the cylindrical shell when the cylindrical shell approaches the boundary, and the influence tends to vanish when the distances between the cylindrical shell and the boundaries exceed certain values. However, the influence of the complex acoustic boundary on the far-field sound pressure of the cylindrical shell cannot be ignored. The far-field acoustic directivity of the cylindrical shell varies with the distances between the cylindrical shell and the boundaries, besides the driving frequency. The work provides more understanding on the vibration and acoustic radiation behaviors of cylindrical shells with complex acoustic boundary conditions. [ABSTRACT FROM AUTHOR]

The free flexural vibration of a cylindrical shell horizontally immersed in shallow water is analyzed in low frequency range using the wave propagation approach. The effects of both the upper and lower fluid boundaries, i.e. , free surface and seabed, are considered with the image method, and the scattering effect of cylindrical shell is neglected. Motions of cylindrical shell and fluid are modeled with the Flügge shell theory and wave equation, respectively. The accuracy of present method is verified through comparison with available experimental works. The modal added mass is introduced to show the influence of shallow water on coupled modal frequency. The influence of shallow water is significant in the case of small water depth and it's the contributions from fluid boundaries. The presence of free surface (seabed) will make negative (positive) contribution to the modal added mass and finally result in the increase (reduction) of coupled modal frequency. But the individual fluid boundary effect will be reduced gradually and finally negligible when the distance between cylindrical shell and fluid boundary increases. The influence of shallow water can not be negligible when the water depth is less than 8 times of shell radius. This work will help to select proper test environment for submerged cylindrical shell. [ABSTRACT FROM AUTHOR]

Understanding the governing parameters and dynamics of turbulent spray atomization is essential for the advancement of fuel injection technologies, but no concrete understandings have been derived previously. The current study investigates the governing parameters and dynamics of turbulent spray atomization by experimental observations of near-nozzle spray phenomena using an X-ray imaging technique. The effects of critical injection parameters such as fuel property, injection pressure and ambient density on near-nozzle liquid feature size and velocity distributions were extensively studied using three injection nozzles having different levels of initial flow turbulence and dispersion. Based on the results, the governing parameters and dynamics of turbulent spray atomization and the issues on the advanced fuel injection control of modern engines were thoroughly discussed. The results showed that fuel and injection pressure effects on spray atomization became insignificant from a critical Weber number which decreased upon the increase in initial flow turbulence and dispersion. The increase in ambient density increased the resultant droplet size at downstream due to the faster deceleration of spray which brought the atomization termination location closer to the nozzle exit. The spray atomization was terminated at the location of ca. 72% exit velocity regardless of the injection condition. [ABSTRACT FROM AUTHOR]

The far-field acoustic radiation of a cylindrical shell with finite length submerged at finite depth from the water surface is studied. Two steps are utilized to solve the problem. The first step is to determine the vibration response of the submerged cylindrical shell by using an analytical method and the second one is to determine the far field sound radiation with the boundary element method. To address the vibration responses of the shell analytically, the cylindrical shell and surrounding fluid are described by the Flügge shell equations and Laplace equation in the cylindrical coordinate system respectively. The free surface effect is taken into consideration by using the image method and the Graf's addition theorem. The reliability and efficiency of the present method are validated by comparison with the finite element method. Then, based on the vibration responses of the shell obtained from the first step, the far-field sound pressure is computed by using the boundary element method. It is found that the vibration of the cylindrical shell submerged at finite depth from the free surface tends to be the same as that in infinite fluid when the submerged depth exceeds a certain value. The frequency and the submerged depth have crucial effects on the fluctuation of the far-field sound pressure, while for the curve of sound pressure level versus immersion depth, the ratio of the distance between the adjacent peak points of sound pressure to the wavelength is independent of the frequency. Moreover, the petal number of the directivity of the far-field sound pressure increases with the increase of the frequency and the submerged depth. The work provides more understanding on the vibration and acoustic radiation behavior of a finite cylindrical shell submerged at finite depth. [ABSTRACT FROM AUTHOR]

In order to improve the engine thermal efficiency with reduced emissions, substantial studies have been carried out to investigate the factors affecting the fuel spray characteristics such as nozzle geometry, fuel property, and injection and ambient conditions. However, most of the previous studies have focused on the macroscopic structures of the fuel sprays, but detailed structures of internal spray dynamics have not been thoroughly investigated, especially in the near-nozzle region. In this study, the effects of critical injection parameters such as injection pressure, ambient density, fuel, nozzle hole diameter and length on the near-nozzle spray dynamics of multi-hole gasoline-direct-injection injectors were investigated using X-ray phase-contrast imaging and visible light imaging. Then, the scaling potential of the near-nozzle spray dynamic structure under various injection parameters was surveyed based on the gas jet theory. The results showed that the density ratio of the fuel and surrounding gas and spray angle are the governing factors of the near-nozzle spray dynamic structure. By introducing the governing factors as the scaling variables, the near-nozzle spray dynamic structure under various injection parameters can be scaled with near 90% correlation performance. However, the scaled dynamic path in the near-nozzle region is different with that of the gas jets that requires modifications of conventional gas-jet-based dynamics models for application to the near-nozzle region. [ABSTRACT FROM AUTHOR]

A completely submerged underwater vehicle is modeled as a conical-cylindrical-spherical combined shell, the vibro-acoustic response near free surface of which is rarely analyzed in existing studies. In this paper, a Ritz-Legendre spectral method is proposed to analyze the vibro-acoustic response of combined shells under different submerged depths from the free surface. A theoretical structural model is established based on the Love shell theory, virtual spring technology and coordination relationship between displacements and rotation angle of adjacent subshells. The half-space external acoustic field model with the free surface is formulated by the Legendre spectral method, image method and Kirchhoff–Helmholtz boundary integral equation. The unified displacement admissible function of each subshell is expanded as Legendre orthogonal polynomial along generatrix direction and Fourier series along circumferential direction. The free surface treated as an ideal infinite acoustic soft boundary is substituted into acoustic wave equation and the half-space Green's function is obtained. The key technology to construct final coupled governing equation is how to expand the half-space Green's function with two-dimensional Fourier transform. Computed results are compared with those of the references and finite element method. The convergence, applicability, and correctness of the present method are verified. Influence of the free surface on the vibration and far-field acoustic radiation of combined shells under different submerged depths is analyzed, providing engineering significance for predicting external acoustic radiation of complicated combined shells with free surface. • A semi-analytical method is proposed to solve the vibro-acoustic response of combined shells submerged near free surface. • Two-dimensional Fourier transform is employed to solve half-space Kirchhoff-Helmholtz equation. • The submerged depth has significant influence on far-field acoustic radiation and vibration response of combined shells. • Legendre-Gauss spectral method can solve acoustic-structure coupled problems of combined shells with free surface. [ABSTRACT FROM AUTHOR]

Based on the principle of energy variation, a calculation model for the free vibration characteristics of a cylindrical shell with a finite submerged depth considering the influence of the free liquid surface is established in this paper. First, the Euler beam function is used instead of the shell axial displacement function to obtain the shell kinetic energy and potential energy. Then, by using the mirror image method, the analytical expression of the fluid velocity potential considering the free surface is obtained, and the flow field is added to the system energy functional in the form of fluid work. Then the energy functional is changed to obtain the shell–liquid coupled vibration equation. Solving the equation can obtain the natural frequencies and modes of the structure. The comparison with the finite element calculation results verifies the accuracy of the calculation model in this paper. The research on the influence of the free liquid surface shows that compared to the infinite domain, the free liquid surface destroys the symmetry of the entire system, resulting in a difference in the natural frequency of the positive and negative modes of the shell, and the circumferential mode shapes are no longer mutually uncoupled trigonometric functions. The existence of free liquid surface will also increase the natural frequency of the same order mode, and the closer to the free surface, the natural frequency is greater. As the immersion depth increases, the free vibration characteristics will quickly tend to the result of infinite domain. Additionally, when the immersion depth is equal to or greater than four times the radius of the shell structure, it can be considered that the free liquid surface has no effect. These law and phenomena have also been explained from the mechanism. The method in this paper provides a new analytical solution pattern for solving this type of problem. [ABSTRACT FROM AUTHOR]

A semi-analytical method is presented to analyze free vibration response of beam-plate-shell combined structures with general boundary conditions. Based on the beam-plate-shell energy theory, the coupled annular plate-conical-cylindrical-spherical shell with stiffened rings and bulkheads regarded as the theoretical model is constructed. The unified displacement admissible functions of each substructure are expanded as modified Fourier series and auxiliary convergence functions along generatrix direction and Fourier series along circumferential direction. Virtual spring technology is adopted to express the energy stored at the junction of adjacent substructures and both boundaries. The energy variational procedure and Ritz method are used to obtain the vibrational governing equation of the combined structure. The present method provides an analytical way for the vibrational response of complicated combined structures. The convergence, accuracy and reliability are validated by comparing the free vibrational response with those of the references and finite element method. Some numerical examples show effects of different boundary conditions on the free vibration. And the influence of stiffened rings and bulkheads treated as Euler-beams and annular plates is also discussed from quantity, size and spatial distribution, offering a feasible way to design the reinforced structures and optimize the bulkheads in engineering problems. [ABSTRACT FROM AUTHOR]

• The vibration characteristics of a two-layer beam are solved by the energy method. • Solving the defect of insufficient stiffness about acoustic black hole. • Proposing a damping design with lightweight and strong vibration suppression ability. • Providing the engineering design guidance of acoustic black hole damping layer. Inspired by the thickness reduction and wave focusing characteristics of the acoustic black hole (ABH) effect, a so-called ABH-damping layer (ABHD) is proposed for the broadband vibration reduction of a host structure, different from the common-used uniform thickness damping layer (UNID). The ABHD has a lighter weight and shows better vibration suppression ability. It can overcome the defect that ABHs cannot serve as the main load-bearing component due to the stiffness reduction. The primary beam structure and damping layer both follow the Timoshenko beam theory. The null space method handles the continuity between the two-layer structures. Analyses reveal the difference in vibration suppression characteristics between UNID and ABHD, further exhibiting the wave-gathering properties of ABH. The mass reduction ratio of ABHs is presented under different damping material loss factors. Finally, an experiment is conducted to verify the correctness of the proposed method and the feasibility of designing the ABHD. The damping layer's weight of ABHD is reduced by 30.8% less than that of UNID, when the material loss factor is equal to 1.0. This study provides a new method for lightweight, strong vibration suppression performance and wide-band vibration reduction in engineering with the application of ABH. [ABSTRACT FROM AUTHOR]

High proton conductivity with sufficient stability for phosphoric acid (PA) doped polybenzimidazole membranes is critical for applications in fuel cells. Macromolecular cross-linkers with hyperbranched structures have large volumes and many functional groups, which can not only react with polymer backbones to form multiple cross-linked sites, but also provide favorable conditions for subsequent functional group modifications to regulate the interaction between polymers and PA; however, such cross-linkers are rarely exploited in fuel cells. Herein, a series of cross-linked polybenzimidazole membranes were successfully prepared based on a novel hyperbranched cross-linker and the incorporation of numerous quaternary ammonium groups. These cross-linked polybenzimidazole membranes containing a hyperbranched cross-linker and quaternary ammonium groups showed superior performance, in terms of mechanical properties, oxidative resistance and proton conductivity. The tensile strength of the PA doped cross-linked membranes was more than 20.0 MPa. These cross-linked membranes showed only a slight weight loss and no cracks after immersion in Fenton's reagent for 200 h, while the linear membrane was broken into pieces after immersion in Fenton's reagent for 100 h. With low acid loading, the membranes containing cross-linked polybenzimidazole with quaternary ammonium groups still exhibited good conductivity. As a result of the excellent comprehensive properties, the obtained fuel cell based on the membrane with 15% of the hyperbranched cross-linker showed a great power density of 260 mW cm−2, which was 36.8% higher than that of the fuel cell based on the corresponding linear membrane. Image 1 • Novel hyperbranched cross-linked polybenzimidazoles containing quaternary ammoniums were designed. • The QOPBIs showed excellent oxidative stability and tensile stress. • The QOPBIs showed high proton conductivity. • A power density of 260 mW cm−1 was obtained for a fuel cell based on QOPBI-15. [ABSTRACT FROM AUTHOR]

abstract [ABSTRACT FROM AUTHOR]

Rotor-bearing systems are important components of rotating machinery and transmission systems, and imbalance and misalignment are inevitable in such systems. At present, the main challenges faced by state-of-the-art fault diagnosis methods involve the extraction of fault features under strong background noise and the classification of different fault modes. In this paper, a fault diagnosis method based on an improved deep residual shrinkage network (IDRSN) is proposed with the aim of achieving end-to-end fault diagnosis of a rotor-bearing system. First, a method called wavelet threshold denoising and variational mode decomposition (WTD-VMD) is proposed, which can process original noisy signals into intrinsic mode functions (IMFs) with a salient feature. These one-dimensional IMFs are then transformed into two-dimensional images using a Gramian angular field (GAF) to give datasets for the deep residual shrinkage network (DRSN), which can achieve high levels of accuracy under strong background noise. Finally, a comprehensive test platform for a rotor-bearing system is built to verify the effectiveness of the proposed method in the field. The true test accuracy of the model at a 95% confidence interval is found to range from 84.09% to 86.51%. The proposed model exhibits good robustness when dealing with noisy samples and gives the best classification results for fault diagnosis under misalignment, with a test accuracy of 100%. It also achieves a higher testing accuracy compared to fault diagnosis methods based on convolutional neural networks and deep residual networks without improvement. In summary, IDRSN has significant value for deep learning engineering applications involving the fault diagnosis of rotor-bearing systems. [ABSTRACT FROM AUTHOR]

Fuel spray atomization is a critical process that can be optimized to improve fuel efficiency and reduce exhaust emissions for internal combustion engines, especially for gasoline direct-injection engines. Understanding the governing parameters of fuel sprays is essential for the advancement of fuel direct-injection technologies and further improvement of engine performance. However, the effect of the ambient temperature on fuel sprays has not been fully understood yet, especially for flash-boiling spray which is common under some representative engine conditions. In this study, the effects of the ambient temperature on spray characteristics under both non-flash-boiling and flash-boiling conditions were investigated using Mie scattering techniques, and the correlations between spray characteristics and dimensionless numbers were established to study the effects of governing parameters on fuel sprays. The results show that the evaporation of fuel spray was enhanced as the ambient temperature was elevated. In addition, increasing the ambient temperature could enhance the collapse of multi-hole fuel spray under flash-boiling conditions. Such observations indicate that increasing the ambient temperature has a similar effect on the collapse of fuel sprays, compared with decreasing the superheat index (Pa/Ps) of the fuel injected. Therefore, in this study, the effect of ambient temperature on the local superheat degree of fuel spray was accounted for. A universal correlation between spray penetration and the equivalent original superheat index was then found, incorporating the effects from both ambient temperature and superheat index. The formulation introduced above was found to significantly extend the scope of the previous research and provides useful information for the design of fuel injection systems. [ABSTRACT FROM AUTHOR]

• A virtual spring-energy method is used to solve the vibration of periodic ABH beams. • The transmissibility possesses linear superposition with the number of periods. • A combined ABH beam with broadband vibration suppression can be constructed. An acoustic black hole (ABH) structure has a gradual impedance gradient due to the thickness of the section decreasing as a power law, which shows excellent wave gathering and energy dissipation effect. To enhance the vibration suppression ability, periodic ABHs are proposed recently. A virtual spring-energy method (VEM) is adopted to handle the periodic boundary condition of periodic ABHs. The accuracy of the method is verified through the finite element method. The band gap of infinite periodic ABH beam and vibration transmission of finite periodic ABH beam are analyzed. For finite periodic ABH beams, the size of cells affects the attenuation band of vibration transmission, and the number of cells affects the amplitude. There is a linear superposition characteristic between the attenuation amplitude and the number of cells. The effect of damping layer on beams with different cross sections is also discussed. Finally, a combined ABH beam with damping layers of different cell sizes is proposed to achieve wide transmission attenuation bands. [ABSTRACT FROM AUTHOR]

Thermo-acoustic radiation from nano-thin film has been widely reported these years. In this paper, a static magnetic field is introduced to enhance the acoustic power in the multi-field thermo-acoustic generation. The coupled thermo-acoustic system in a static magnetic field shares the same acoustical unit with very few additional components. In the presence of a static magnetic field, thin-film vibration is excited instead of being still in the classical thermo-acoustic system. Not surprisingly, a steady magnetic field has very little impact on the thermo-acoustic generation system when a constant amplitude sinusoidal current is introduced. The oscillation perpendicular to the nano-thin film is driven by the electromagnetic force. The system response of thermo-acoustics and magneto-acoustics can be generally matched when suitable parameters are introduced. The acoustical pressure output can be significantly improved in the presence of a static magnetic field although more electrical input power should be provided in the multi-field thermo-acoustic system. Evidently, the coupled multi-field acoustical system is able to handle more electrical power input and the power input can be more easily dissipated relatively. The results show that the acoustic response of this new multi-filed coupled system can be significantly improved as compared to the classical system without magnetic effects. [ABSTRACT FROM AUTHOR]

An analytical approach for predicting the free vibration and elastic critical load of functionally graded material (FGM) thin cylindrical shells filled with internal pressured fluid is presented in this study. The vibration of the FGM cylindrical shell is described by the Flügge shell theory, where the internal static pressure is considered as the prestress term in the shell equations. The motion of the internal fluid is described by the acoustic wave equation. The natural frequencies of the FGM cylindrical shell under different internal pressures are obtained with the wave propagation method. The relationship between the internal pressure and the natural frequency of the cylindrical shell is analyzed. Then the linear extrapolation method is employed to obtain the elastic critical load of the FGM cylindrical shell from the condition that the increasing pressure has resulted in zero natural frequency. The accuracy of the present method is verified by comparison with the published results. The effects of gradient index, boundary conditions and structural parameters on the elastic critical load of the FGM cylindrical shell are discussed. Compared with the experimental and numerical analyses based on the external pressure, the present method is simple and easy to carry out. [ABSTRACT FROM AUTHOR]

This paper presents a new receptance-based method for the robust assignment of natural frequencies. This method aims to address the deviation of the actually achieved natural frequencies for target natural frequencies when assigning natural frequencies, which usually arises due to uncertainties in passive structural modifications (i.e. mass and stiffness modifications). The mathematical expression is derived for the sensitivity of the target natural frequency to the uncertainties in modification parameters, which are subsequently employed to characterize the potential deviations of the target natural frequencies in the total differential form. The obtained deviation expression is integrated into the optimization calculation of the natural frequency assignment as an extra penalty term to boost the acquisition of highly robust modification parameters. The proposed robust assignment method, as a non-probabilistic technique, can be employed without any knowledge of the probabilistic distribution of uncertainty in modification parameters. Moreover, it uses only the measured frequency response functions (FRFs), preserving the advantage of the receptance method not needing a numerical model. Two numerical examples and a comparison with a typical eigenstructure assignment method (reported in the literature) demonstrate that the proposed method can provide highly robust modification parameter solutions. The application of the proposed method to the natural frequency assignment of a laboratory water-filled pipeline system gives experimental evidence of its effectiveness. [ABSTRACT FROM AUTHOR]

This study proposes the use of a novel nonlinear tuned mass damper inerter device in vibration suppression of the ship propulsion shafting system and evaluates its performance. The device consists of an axial inerter and a pair of lateral inerters to create geometric nonlinearity. The system response subjected to propeller forces is determined by using the harmonic balance method with alternating-frequency-time technique and a numerical time-marching method. The force transmissibility and energy flow variables are employed to assess the performance of the device. The results show that the proposed device can reduce the peak force and energy transmission to the foundation while increase the energy dissipation within the device. Its use can lead to an improved vibration attenuation effect than the traditional mass-spring-damper device for low-frequency vibration. The configurations of the nonlinear inerter-based device can be adjusted to obtain an anti-peak at a resonance frequency of the original system, providing superior vibration suppression performance. [ABSTRACT FROM AUTHOR]

The vibroacoustic study of a horizontal, finite-long cylindrical shell partially submerged in a fluid is presented in this paper. First, the mathematical and physical model of the system is established using two different coordinate systems for the sound field and the structure. Second, using the Galerkin method to deal with the continuity condition for the velocity on the acoustic–structure coupling surface, the matrix relation of the coefficient vector of the sound field and the displacement field is obtained, followed by the analytical solution of the vibration. The accuracy of this new method is verified through numerical simulations, while its broad applicability and reduced computational cost are demonstrated. Moreover, the method is extended to obtain the far-field sound radiation using the stationary phase method. Altogether, the present work introduces a new thought for solving the vibroacoustic characteristics of a partially coupled system consisting of elastic structures and external fluid fields. [ABSTRACT FROM AUTHOR]

The acoustic black holes (ABH) with the power-law profile are applied in many fields, such as vibration control, energy collection, etc. It is widely known that the ABH only works above the cut-on frequency. However, few studies improve the vibration suppression performance of acoustic black hole structures below the cut-on frequency. This paper proposes shunt damping to improve the wave suppression ability of an ABH plate in the low-frequency range. The ABH plate with shunt damping obeys the Kirchhoff–Love plate theory. Based on the Hamiltonian principle, the modified Fourier series is selected as the shape function, and the natural frequency of the ABH plate is calculated by the energy method. Compared with the finite element method results, the correctness of this method is verified. Further, comparing the vibration characteristics of the ABH plate with those of the uniform thickness plate, it can be obtained that the ABH plate has excellent vibration damping performance in high frequency but a poor effect in low frequency. Therefore, a shunt damping with blocking circuits is pasted on one side of the central area of the ABH and successfully suppresses four resonate formants in the low-frequency band. Finally, the high-frequency vibration characteristics of the ABH plate with shunt damping are improved by increasing the thickness of the ordinary damping layer. This paper proposes a shunt damping ABH plate composite structure with excellent vibration suppression performance in both the high-frequency and low-frequency range, providing a new idea for the application of two-dimensional ABH plate structures in vibration control. • A semi-analytical method is employed to solve the vibration of ABH plate with shunt damping. • Piezoelectric patch with an external circuit is equivalent to homogeneous material. • Shunt damping can suppress multiple resonate formants at specified frequencies. • An ABH plate with the shunt and ordinary damping can achieve vibration suppression in low and high-frequency bands. [ABSTRACT FROM AUTHOR]

• A semi-analytical method is proposed to solve the coupled vibration analysis of partially liquid-filled cylindrical shells with internal horizontal plates. • Two coordinate systems are used to depict the motion of the structures and fluid, respectively. • The internal fluid takes into account the linear sloshing effect. • The analytical modeling is considered with both the coupling of the shell with the internal structure and the partial interaction between the shell and partially filled fluid. • The effects of the structures' parameters and liquid effect on the coupling system's free and forced vibration behaviors are studied. A semi-analytical method is proposed to analyze the coupling vibration characteristics of a partially liquid-filled cylindrical shell with an internal horizontal plate, considering the sloshing effect of the free liquid surface. Two coordinate systems are set at the midpoint of the free surface and the geometric center of the cylindrical shell's cross-section, respectively. The Flügge shell and Kirchhoff-love theories are adopted to establish the motion equations of the cylindrical shell and the plate on the structural coordinate system, respectively, in which the displacement functions are expressed with the wave propagation method. The liquid velocity potential functions are described in the symmetrical/anti-symmetrical forms based on the liquid coordinate system, which satisfies Laplace's equation. The coupling governing equations are deduced by the continuous conditions of force and displacement on the fluid-shell interface. After that, the coupling vibration responses can be solved. The accuracy of the present method is verified by the comparison with the finite element method. The influences of the structures' parameters and liquid effect on the coupling system's free and forced vibration behaviors are discussed, and the sloshing behaviors of the internal fluid are also discussed under different parameters. [ABSTRACT FROM AUTHOR]

The effects of high temperature exposure on the low velocity impact behaviors and damage mechanisms of all-composite pyramidal truss core sandwich panels were investigated by experiment in this paper. The composite sandwich panels were manufactured from unidirectional carbon/epoxy prepreg and exposed to different temperatures for 6 h. The impact tests of exposed specimens were performed at three different energy levels, and the effects of exposure temperature and impact energy level on the damage mechanism, absorbed energy and maximum impact force were analyzed. The impact-damaged specimens were subsequently subjected to in-plane compressive tests in order to investigate the effect of exposure temperature and impact energy level on the compressive failure load. The results have shown that the high temperature exposure has a significant effect on impact properties and damage mechanisms of specimens. The fiber fracture, node failure, delamination and buckling were observed during low velocity impact tests and the extent of damage area was significantly affected by exposure temperature. In addition, the absorbed energy increased with increasing exposure temperature, while the maximum impact force and compressive failure load after impact decreased with increasing exposure temperature due to the degradation of the matrix properties and fiber–matrix interface properties at higher temperatures. [ABSTRACT FROM AUTHOR]

While large herbivores are critically important components of terrestrial ecosystems and can have pronounced top‐down effects on plants, our understanding of the underlying mechanisms driving these effects remains incomplete. Large herbivores can alter plant growth, reproduction, and abundance through direct effects (predominantly consumption) and through indirect effects via altered interactions with abiotic factors and other species. We know considerably less about these indirect effects than the direct effects. Here, we integrate medium‐ and small‐scale field experiments to investigate how a large vertebrate herbivore, cattle (Bos taurus), affects the aboveground biomass of a dominant forb species, Artemisia scoparia, via diverse direct and indirect pathways in a temperate grassland in northeast China. Although cattle consumed this forb, its biomass increased significantly in response to grazing, due to multiple indirect positive effects that outweighed the direct negative effects of consumption. Cattle preferentially consumed the competing grass Leymus chinensis, and altered Artemisia microhabitats by reducing total plant cover and litter biomass and by increasing the abundance of co‐occurring ant species (e.g., Formica spp. and Lasius spp.). This led to additional indirect positive effects on A. scoparia likely due to (1) increased light availability in understory layers and other limiting resources (e.g., soil nutrients and moisture) caused by removal of competitors and plant litter at the soil surface and (2) the changes in resource availability (e.g., soil nutrients and moisture) associated with ant colonies. Our results show that large herbivores can affect plant growth not only via direct consumption, but also via multiple indirect effects. Focusing on the causes and consequences of herbivore‐induced indirect effects will not only help us to better understand the influence of these animals in ecological systems, but will also lead to more effective land management and conservation practices in the regions they inhabit. [ABSTRACT FROM AUTHOR]

• A novel linear expression method is used for the vibration analysis of conical-cylindrical-spherical shells. • The convergence of this method is related only to the numbers of the shape function. • This linear expression method can be used for arbitrary boundary conditions. Composite shells are increasingly used in underwater vehicles, aerospace and other engineering fields. In this study, a linear expression method (LEM) was developed for the efficient vibration analysis of conical–cylindrical–spherical shell structures. Herein, the constraint and continuity conditions were expressed in matrix form, and a full-rank matrix was derived via the Gaussian elimination method. Then, it was possible to linearly express the unknown coefficients in the original equations. Consequently, combined with the energy method, the vibration characteristics of composite shells could be obtained. A conical–cylindrical–spherical shell was considered as an example. Its natural frequencies, vibration modes, and forced vibration analysis were carried out, and the results are compared for verification with those obtained by the finite element method (FEM) and those found in the literature. It is shown that the proposed LEM can be up to five times faster than FEM. Concentrated mass points and forced vibration were also considered, and the partial coupling between the shell and the mass points led to the breaking down of the circumferential symmetry of the cylindrical shell. The convergence of LEM is related only to the number of truncated terms of the shape functions; thus, it exhibits strong convergence and reduced computational cost, and offers a wide range of potential applications. [ABSTRACT FROM AUTHOR]

• Innovative design of a new composite coating with transversely arranged SWCNTs. • A novel semi-analytical approach with multi-scale features is proposed. • A global TMM for vibroacoustic properties of orthotropic materials is developed. • The new coating breaks the general lower limit of 500 Hz@0.5 to 193.1 Hz@0.5. This paper presents a new underwater composite coating with transversely arranged single-walled carbon nanotubes (SWCNTs) to broaden the lower frequency limit of sound-absorbing and improve the broadband absorption bandwidth. Meanwhile, a novel semi-analytical approach integrating molecular dynamics simulation methodology and global generalized transfer matrix method (6 × 6) is proposed to predict the corresponding sound absorption characteristics. Then, the correctness and effectiveness of the present theoretical model are validated by means of an acoustic-structure fully coupled finite element simulation and theoretical predictions in turn. At last, influence laws of ten critical parameters on sound absorption coefficients are explored to reveal the multiple energy-dissipation mechanisms. The results show that the 0.5 absorption bandwidth of this coating is [0.1931, 50] kHz, which breaks the lower limit 0.5 kHz of the conventional low-frequency band and has a high-performance broadband absorption potential. [ABSTRACT FROM AUTHOR]

In this paper, a semi-analytical study is presented to solve the linear liquid sloshing frequencies and mode shapes of a three-dimensional partially filled horizontal cylindrical container. The internal liquid of the tank is regarded as the incompressible, inviscid fluid, whose velocity potential function satisfies the Laplace function and the free surface gravity wave function. According to the sloshing modal shapes, the velocity potential function is expressed as symmetric and antisymmetric modes, respectively. The normal velocities of the fluid are set to be zero to model the rigid boundary condition on the fluid-structure interface of the container. Two coordinate systems are introduced in the model. The fluid field coordinate system is set at the midpoint of the free liquid surface. The other coordinate system, the structure coordinate system, is established at the geometric center of the tank cross-section. Through the coordinate transformation and the continuous boundary condition, the motion equation of the system could be obtained. The Galerkin method is employed to solve the governing equation and acquire the sloshing frequencies. Simultaneously, a series of experiments are carried out to investigate the sloshing movement with different liquid depths, and the low-order sloshing frequencies and mode shapes are obtained through the experiments. The accuracy of the semi-analytical method is verified by comparing the results with the published results, the finite element results, and the experimental results. The effects of the liquid depths and the tank length on the sloshing motion are investigated as well. • A semi-analytical method is proposed to solve the small-amplitude sloshing of cylindrical shell with arbitrary liquid depths. • Double coordinate systems are used to depict the motion of the system. • An experiment is carried out to investigate the liquid sloshing movements. • The present method is validated by the comparison with published, FEM and experimental results. • The effects of the different parameters on sloshing frequencies are studied. [ABSTRACT FROM AUTHOR]

Water-filled double-layer structures are typical hull structures. However, the effect of the carried water has often been neglected in previous collision studies. The carried water couples with the hull structure and participates in the energy absorption process, which reduces the collision damage done to the hull structure. This paper focuses on the effects of compressible carried water on the collision characteristics of a hull structure. Therefore, collision experiments with a simplified double-layer structure (water tank) were performed, and the corresponding collision process was simulated with the finite-element method. The two kinds of pressure (a shock wave and pressure disturbance) generated in the carried water when the water tank collides with a striker were investigated. By comparing the dynamic characteristics of empty and completely filled water tanks, it can be observed that the pressure of the carried water can reduce the displacement of the outer plate and change its deformation shape. Furthermore, the effects of pressure on the collision force and displacement of the inner plate were investigated. Finally, the collision characteristics of a typical water-filled side structure are presented as an example. • A collision test of a water-filled double-layer structure was designed and carried out. • Carried water can effectively reduce the collision damage to the outer plate. • Carried water may lead to the outer plate's reversed deformation after collision. • The collision load causes a pressure disturbance and shock wave in the carried water. [ABSTRACT FROM AUTHOR]

A vibration isolation means for a human-seat-boat-water dynamic interaction system subject to sea waves is proposed, for which to be numerically analyzed, the governing equations with numerical solution approaches are developed. The key idea is adopting electromagnetic isolators to replace often-used seat-damper to reduce vibrations by harvesting wave energy. The human body is modelled as a mass supported by a spring-damper connected to a seat, that through the electromagnetic isolator connected to a boat simplifying as a uniform beam-like vessel travelling in sea way. The wave force in the model is an approximate form commonly used in dynamic analysis of marine engineering, consisting of three components proportional to the relative motion of ship to the water, which adds additional mass, stiffness, and damping onto the ship. The parameters in the simulations are chosen from the practical designs or experimental/numerical reports. The simulation results reveal the effects of integrated interactions on the natural frequencies and dynamic responses of the ship subjected to short/long water waves and show very large reductions of human vibration level and effectively collecting wave energy. This confirms the proposed numerical model for ship vibration reduction and wave energy collection is attractive to simulate this complex integrated interaction system, and the proposed means based on electromagnetic isolators is no doubt to realize the aim of the paper. Some guidelines for designing this type of isolators are presented, which would be one of further develop directions for the global plan seeking/collecting green energies. • A new system design with electromagnetic isolator is proposed to reduce vibration and harvesting energy at same time. • The integrated coupling system is numerically investigated considering a typical ship structure and wave averments. • Results confirm energy harvesting means are effective, which may be a research direction to global green energy plan. • Practical guidelines for designing this type of isolators are presented as a reference for engineering applications. [ABSTRACT FROM AUTHOR]

In this article, a thermally and magnetically induced monodirectional acoustic transducer is introduced with applications. An alternating thermal field is aroused by a sinusoidal current on a nano-thin film and an acoustic field is further excited due to the thermo-acoustic effect. A periodic magnetic field at the same frequency is concurrently applied to excite a fresh acoustic field in order to derive an enhanced sound pressure output. An analytical model for the mixed acoustic emitting system is established and the acoustic response is analyzed theoretically. An improved parabolic approximation relationship with only first-order Taylor's expansion is applied on the thermo-acoustic decoupling to obtain the thermo-acoustic propagating wave numbers. In addition, the oscillation of nano-thin film is driven by the magnetically induced Ampère's excitation in magneto-acoustics that introduces an additional mass effect. Moreover, thermo-acoustic and magneto-acoustic responses share the identical frequency but in a distinct phase difference. By designing a proper system configuration on the amplitude and phase of magnetic flux density, the backside acoustic field can be made to disappear. Furthermore, non-dimensionalization and numerical methods are applied to determine the amplitude of magnetic flux density for monodirectional acoustic field in varying parameters. Image 1 • A new model with theory and solutions thermo-magnetic-acoustic systems. • A novel high-precision parabolic approximation is introduced for thermo-acoustics. • Added masses by both thermo-acoustics and magneto-acoustics are considered. • A proper design on external magnetic field for monodirectional acoustic transducer. [ABSTRACT FROM AUTHOR]

• This study proposes a new method with a wide application scope and good accuracy. • Antisymmetry modal frequencies are different from the symmetry ones. • Far-field sound pressures comes up to be maximum just right below the shell. In this study, a semi-analytical method is proposed to study the vibration and acoustic radiation of a two-dimensional cylindrical shell partially coupled with internal fluid. Different from the conventional vibroacoustic model of cylindrical shells, two different coordinates are established to describe the motion of the shell and the internal fluid respectively. One coordinate system is established on the free surface, where the sound pressure release boundary condition is satisfied automatically by constructing a sine series expression of sound pressure. Meanwhile, with the center of the shell's cross section as the origin, the other is established to describe the motion of the shell. Then the Galerkin method and the coordinate transformation technique are adopted to deal with the velocity continuous condition on the partially coupled interface. Finally, the vibroacoustic response can be solved theoretically. The applicability and reliability of the present method are validated by comparison with the finite element method via the free vibration, forced vibration and sound radiation cases. The present method is also extended to deal with the vibration and sound radiation of shell coupled with external fluid successfully. Generally speaking, this study proposes a new method to the solution of the vibroacoustic behaviours of an elastic cylindrical shell partially coupled with fluids theoretically, with a wide application scope and good accuracy. [ABSTRACT FROM AUTHOR]

Flash boiling sprays have been widely studied recently because of its potential in generating fuel sprays with improved atomization efficiencies. Due to the strong multiphase influence, the exact spray atomization mechanisms of flash boiling sprays are not well understood yet, especially in the near-field where the optical depth is usually high for optical measurements. This investigation utilized a two-hole gasoline direction injection fuel injector to analyze the near-field atomization performance of a single spray plume under flash boiling conditions with a lower injection pressure to avoid the interference from dense sprays under higher injection pressures. High-speed backlit and Schlieren techniques were used to capture the liquid phase and gas phase distributions in the near-field and a microscope was incorporated to obtain detailed structure information of the fuel spray near the nozzle exit. Boundary conditions including fuel temperatures and ambient pressures were varied to study fuel atomization under different superheat indices and Cavitation numbers. Plume characteristics at different stages of the injection were investigated and significant multiphase influence can be found within the transitional flash boiling regime, including a two-zone atomization behavior at the beginning of the injection, a liquid skirt structure during the fuel injection, and a fishnet ligament pattern at the end of injection, respectively. This work also examined the impact of Cavitation number, superheat index, and ambient pressure on the properties of the external spray and such influence was represented by the near-field cone angle defined from near-field measurements. [ABSTRACT FROM AUTHOR]

• A measurement-based method for determining optimal support layout is proposed. • Only a small number of modal parameters need to be measured in this method. • This method can reduce responses of a post-manufactured pipeline at resonance. • The proposed method is demonstrated on a real L-shaped pipeline system. Layout optimization of elastic supports is an effective approach to address the resonance problem of an industrial post-manufactured pipeline. However, previous investigations of support layout optimization of a post-manufactured pipeline usually require establishing or updating the numerical model of the whole pipeline system, which may lead to time-consuming calculations and poor optimization results. In order to overcome these drawbacks, a new measurement-based layout optimization method is proposed in this method. Only a small number of experimental modal parameters (natural frequencies, damping ratios, and mode shapes) are needed in this method. Resonance avoidance, in this method, is recast as an assignment of natural frequencies, and the target natural frequencies are realized by performing structural modification in two stages. In addition, each of the elastic supports is viewed as a mass-spring-damper sub-system in this paper, which is represented by its measured dynamic stiffness and does not need a pre-determined simplified form. A numerical example demonstrates that the proposed method can accurately realize the target natural frequencies. The application of the proposed method to optimize the support layout of a real L-shaped pipeline system provides experimental evidence of its effectiveness. This experiment is the first attempt to achieve the layout optimization of pipeline supports for solving the resonance problem of a post-manufacture pipeline, entirely relying on the measured modal data. [ABSTRACT FROM AUTHOR]

The high cost of operation and maintenance can impede the development of offshore wind turbines (OWTs). With advancements in detection technology, condition-based maintenance (CBM) has emerged as a promising approach to managing maintenance. Numerous CBM polices have been studied to achieve a cost-effective maintenance. However, little research has been conducted on discovering the cost-optimal CBM policy for OWTs. With this motivation, a deep reinforcement learning (DRL) framework for exploring the cost-optimal CBM policy is proposed in this paper. Four CBM policies (i.e. uniform or dynamic inspection interval, and fixed or adaptive repair threshold) are formulated as the Markov decision process model. Two DRL algorithms (deep Q network and proximal policy optimization) are applied to derive the dynamic inspection interval and the adaptive repair threshold. To illustrate this framework, a fatigue OWT component is used as an example. The four policies are optimized under varying conditions to find the cost-optimal CBM policy. Moreover, performance comparison of DRL algorithms is performed. The case study illustrates the advantage of DRL in deriving optimal maintenance policies for fatigue-sensitive OWT components and highlights the interrelationship between maintenance policy and economic performance. This paper concludes by discussing the effect of cost elements on the CBM policies. • A DRL framework is proposed to derive the cost-optimal CBM policy for OWTs. • CBM policies with different inspection intervals and repair thresholds are studied. • The performance of two DRL algorithms is compared under different conditions. [ABSTRACT FROM AUTHOR]

International Marine Organization is promoting stricter carbon emission reduction targets, and the influx of environmental regulations presents compliance risks for maritime sector. Stakeholders need to take decarbonization performance indicators into account in ship routing to maintain regulatory compliance. To meet decarbonization goals, a decision support method related to environmental regulatory compliance is necessary for voyage optimization. To this end, this paper presents a digital twin-enabled framework for real-time decarbonization regulatory compliance prognosis in ship routing. The proposed framework tracks real-time carbon intensity and identifies opportunities for reducing operational risks associated with decarbonization goals. The digital twin approach leverage real-time environmental and operational data for improved estimation of vessel-specific regulatory compliance probability along the voyage. An improved dynamic programming algorithm is used for ship routing. The presented framework is versatile in dealing with various decarbonization regulations to provide routing decision support. An illustrated case of a container ship sailing across the South China sea is presented to demonstrate the applicability of the framework. [Display omitted] • A digital twin framework for prognosis of ship decarbonization regulatory compliance is developed. • Regulatory compliance is estimated by probabilistic analysis from a data-driven emission model. • The proposed framework is versatile to deal with different decarbonization regulations including EEXI and CII. • A case study of real-time ship routing considering compliance probability is presented. [ABSTRACT FROM AUTHOR]