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Printing electronic components by screen printing with the excellent printing quality, high efficiency, and environmental protection has broad application prospects in additive manufacturing. However, because conductive-ink blocks the screen, printing efficiency and quality decreased in the printing process. Thus, it is pivotal to explore adhesion factors from the interaction of conductive ink and screen. Herein, according to the transfer process of screen printing ink, solid-liquid wetting theory, and adhesion mechanism, we establish a liquid bridge adhesion model between two plates and obtain the functional relationship between the adhesion force and its influencing factors. Fluent software verifies the adhesion force model's conclusion to get the influence trend of the adhesion force on the ink residue. At last, by establishing a liquid bridge tensile fracture test, we gain experimental results consistent with the theoretical model and numerical simulation results. It is demonstrated that solid-liquid contact angle, tensile distance, and liquid volume are the main factors affecting the change of solid-liquid adhesion. The increase of tensile distance and contact angle will affect the adhesion force. The smaller the maximum solid-liquid adhesion during the initial stretching of the liquid bridge, the less the residual amount remained on the solid surface. By means of screen modification, the adhesion between conductive ink and screen can be reduced; meanwhile, the efficiency and quality of printed products can be improved. What's more, it also provides a valuable reference for the modification of screen printing electronics. [ABSTRACT FROM AUTHOR]

In order to further study the cushioning performance of concave hexagonal cores (CHCs) and expand their application range, the in-plane finite element model of CHCs is established in this paper. A dynamic cushioning coefficient method was proposed to characterize the cushioning performance of CHCs. The dynamic cushioning coefficient curve and minimum dynamic cushioning coefficient (MDCC) of CHCs with different impact velocities and structural parameters are obtained. The influence rules of structural parameters and impact velocities on the MDCC are analyzed; the deformation mode and transformation empirical formula are also obtained. The results show that when other parameters are constant, the MDCC of CHCs decreases with the increase of impact velocity, increases with the increase of wall thickness and side length ratio, and decreases with the increase of expansion angle. The theoretical analysis is consistent with the finite element results, which further verifies the reliability of the model. This paper provides a solid theoretical basis for the industrial application of the cushioning performance of CHCs and forms a key technical support. [ABSTRACT FROM AUTHOR]

Aiming at the sound source localization of mechanical faults in a strong reverberation scenario with multiple sound sources, this paper investigates a mechanical fault source localization method using the U-net deep convolutional neural network. The method utilizes the SRP-PHAT algorithm to calculate the response power spectra of the collected multichannel fault signals. Through the utilization of the U-net neural network, the response power spectra containing spurious peaks are transformed into "clean" estimated source distribution maps. By employing interpolation search, the estimated source distribution maps are processed to obtain location estimations for multiple fault sources. To validate the effectiveness of the proposed method, this paper constructs an experimental dataset using mechanical fault data from electromechanical equipment relays and conducts sound source localization experiments. The experimental results show that the U-net network under 0.2 s/0.5 s/0.7 s reverberation time can effectively eliminate spurious peak interference in the response power spectrum. As the signal-to-noise ratio decreases, it can still distinguish the sound sources with a distance of 0.2 m. In the context of multifault source localization, the method is capable of simultaneously locating the positions of four fault sources, with an average localization error of less than 0.02 m. The method in this paper effectively eliminates spurious peaks in the response power spectra under conditions of multisource strong reverberation. It accurately locates multiple mechanical fault sources, thereby significantly enhancing the efficiency of mechanical fault detection. [ABSTRACT FROM AUTHOR]

As coal mining gradually moves to deep earth, rock bursts have emerged as one of the main disasters threatening the safety of coal production. It is beneficial to conduct economic and effective prevention and control work by evaluating the bursting liability and improving the bursting liability evaluation system. In this paper, based on the energy transfer model, the relationship between the bursting energy index and the mechanical parameters of coal bodies is obtained by testing the bursting liability of 16 coal seams stratified in three coal mines. According to the bursting energy index and the elastic energy index, the parameter φ is defined to represent the energy release ratio of coal. This paper thus presents a method to evaluate the bursting liability as the product of the energy release ratio and energy transfer ratio and provides a definition for the energy transfer index. The results show that the bursting energy index of coal is closely related to its mechanical parameters. The prepeak deformation energy exhibits a strong positive correlation with uniaxial compressive strength and peak strain. The energy release ratio parameter φ and bursting energy index have high sensitivity and wide applicability. The results of the energy transfer index Ω = βφ are consistent with the results of bursting liability identification, which can better reflect the bursting liability, and can be used as the basis for judgment when the " ∗ " result is obtained in bursting liability identification. It is anticipated that this approach will become an important evaluation index for bursting liability identification. [ABSTRACT FROM AUTHOR]

Under the condition of weakly cemented soft rock in Western China, the surrounding rock deformation of gob-side entry is obvious, especially under the influence of fault, and the problem of surrounding rock control becomes increasingly prominent. To solve this issue, this paper firstly studied and obtained the evolution law of the ground pressure appearance of the gob-side entry in the fault area, then put forward the concept of surrounding rock control in the fault area of the gob-side entry, put forward a targeted pressure relief + increase preload + passive reinforcement parallel to the roadway surrounding rock strengthening control scheme, and carried out field applications. The results show that the roof subsidence and mining side heave of the roadway in the fault area increase significantly, accompanied by the characteristics of broken cables, the length of the broken cable is 0.2 m–0.6 m, and the breaking process is divided into multiple breaks. The stress evolution of gob-side entry in fault area presents a stage characteristic of "rapid growth-stable." The surrounding rock control effect is improved under the bolt cable high pre-tightening support, and the roadway deformation is effectively controlled under the pressure relief + active + passive support, with a good application effect. [ABSTRACT FROM AUTHOR]

The magnitude of pretension force serves as an important indicator of the effectiveness of anchor bolt active support and is one of the significant factors influencing the stability of tunnel surrounding rock. Therefore, in practical engineering, it is crucial to establish the relationship between pretension torque and pretension force. However, current research in this field has some limitations. With a specific mine in western China as the engineering background, this paper first analyzed the influence factors of surrounding rock deformation and failure, established a mechanical model for pretension structure of anchor bolt support, and derived the quantitative relationship between pretension torque and pretension force based on hypothetical conditions. Finally, it proposed the loss effect of anchor bolt support and modified the pretightening loss coefficient for engineering application. The research results show that the actual pretightening force of anchor support is lower due to the influence of deep soft coal seam, which leads to failure of coal pillar under mining stress. The loss effect of surrounding rock on pretightening force was represented by a coefficient k, and the modified value of the coefficient was calculated as 0.19∼0.43. By applying the modified relationship between pretightening torque and pretightening force, it was found that the actual pretightening torque of 300 Nm applied to 11307 return air roadway effectively controlled surrounding rock deformation and failure, with coal pillar displacement less than 120 mm. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative approach, Deep Multiscale Soft-Threshold Support Vector Data Description (DMS-SVDD), designed for the detection of anomalies and prediction of faults in heavy-duty gas turbine generator sets (GENSETs). The model combines a support vector data description (SVDD) with a deep autoencoder backbone network framework, integrating a multiscale convolutional neural network (M) and soft-threshold activation network (S) into the Deep-SVDD framework. In comparison with conventional methods, such as One-Class Support Vector Machine (OCSVM) and autoencoder (AE), DMS-SVDD demonstrates improvements in accuracy (by 22.94%), recall (by 32%), F1 score (by 12.02%), and smoothness (by 39.15%). The model excels particularly in feature extraction, denoising, and early fault detection, offering a proactive strategy for maintenance. Furthermore, the DMS-SVDD demonstrated enhanced training efficiency with a reduction in the convergence rounds by 66% and overall training times by 34.13%. The study concludes that DMS-SVDD presents a robust and efficient solution for gas turbine anomaly detection, with practical advantages for decision support in turbine maintenance. Future research could explore additional refinements and applications of the DMS-SVDD model across diverse industrial contexts. [ABSTRACT FROM AUTHOR]

The vibration properties of the submerged sandwich cylindrical shell with a viscoelastic core are investigated in this paper. Considering the acoustic-structure coupling, the analytical model of the submerged sandwich cylindrical shell that can handle three medium conditions including fluid-filled, fluid-loaded, and fluid-filled and -loaded is derived based on the wave propagation approach and the Flügge thin-shell theory. The vibration properties of the sandwich cylindrical shell under different medium and boundary conditions are analyzed, followed by a comparison of the damping effect of the constrained damping layer. Finally, an analysis is conducted on the influence of thicknesses of viscoelastic and constrained layers on vibration spectrum and natural frequency under fluid-filled and -loaded conditions. An experimental platform was established to conduct relevant experiments. Several important conclusions can be drawn. [ABSTRACT FROM AUTHOR]

The composite-laminated rotationally stiffened plate is widely applied in aviation, aerospace, ship, machinery, and other fields. For structural design and optimization, to investigate the vibration characteristics is important. In this paper, a modeling method of composite-laminated rotationally plate is established. The first-order shear deformation theory (FSDT) and the modified Fourier series are applied to construct the admissible displacement function of the stiffened plate-coupled systems. On this basis, the energy function of composite-laminated rotationally stiffened plate is established. Combined with the artificial virtual spring technology, the proposed theory could be used to analyze the vibration characteristics of composite-stiffened plate-coupled systems with various classical boundary conditions or arbitrary elastic boundary conditions. The Rayleigh–Ritz method is used to solve the energy function. Thus, the vibration characteristics of the composite-laminated rotationally stiffened plate are obtained and analyzed. The correctness of the theoretical analysis model was verified through modal experiments. On this basis, the effect of some important parameters on the vibration characteristics of stiffened plate structures is studied, such as the number, thickness, and width of the laminated stiffener, varying structural parameters, and different boundary conditions. This study can provide the theoretical basis for the vibration and noise reduction of such structures. [ABSTRACT FROM AUTHOR]

The rolling bearing is one of the commonly used mechanical components in rotating machinery, and its health directly affects the normal operation of equipment. However, the fault signal of rolling bearing is susceptible to noise interference, which makes it difficult to extract the fault characteristics of the rolling bearing and thus affects the accuracy of the diagnosis results. To address this problem, this paper proposes a method by using a snake optimization algorithm to optimize variational mode decomposition (SOA-VMD) and applies it to the extraction of the fault feature of rolling bearing. First, the minimum Shannon entropy to kurtosis ratio (EKR) is used as the fitness function of SOA to search for the best parameter combination of VMD. Second, the optimized VMD is used to decompose the vibration signal of rolling bearing to obtain K intrinsic mode functions (IMFs). Then, the IMF with the most fault information is selected for reconstruction through EKR. The Teager–Kaiser energy operator (TKEO) spectrum analysis is performed on the reconstructed signal. Finally, this method is used to analyze the simulation signal and rolling bearing vibration signal and compared with empirical mode decomposition (EMD), ensemble empirical mode decomposition (EEMD), and complete ensemble empirical mode decomposition adaptive noise (CEEMDAN) algorithms to verify the feasibility and effectiveness of the SOA-VMD method. [ABSTRACT FROM AUTHOR]

Since the development of industry, sound absorption and noise reduction have gradually become an urgent problem to be solved. Lightweight polymer film materials are very effective in response to sound waves, and sound waves can easily cause vibration of the film, which can convert sound energy into vibration and film friction to achieve sound absorption. The application conditions of the film material are very harsh, that is, a support body is required to fix the film and the film needs to be tensioned. The film is very thin and easy to damage. The idea of this research is to transform the film into a bubble structure and use a large number of film bubbles to form a cavity structure material. As a unit of the sound absorption structure, bubbles can avoid damage to the film. In this paper, commercial polyvinyl chloride film bubble materials are used to prepare two kinds of film multicavity structure materials, and the sound absorption performance of this film multicavity structure material is studied. The research results show that this film multicavity structure material has very excellent broadband sound absorption performance, which changes the narrow band sound absorption properties of the usual film single cavity. The average sound absorption coefficient can reach 0.84 in frequency range from 500 Hz to 6400 Hz. This structural material has a single peak sound absorption curve at the middle and low frequency bands, which is the characteristic of resonance sound absorption. And at the middle and high frequency bands, it exhibits the characteristics of broadband sound absorption. The film multicavity structure material has both cavity sound absorption and broadband sound absorption characteristics. [ABSTRACT FROM AUTHOR]

This paper presents a structural health monitoring method based on artificial neural networks (ANNs) capable of detecting, locating, and quantifying damage in a single stage. The proposed framework employs a supervised neural network model that uses input factors calculated by modal parameters (natural frequencies or mode shapes), and output factors that represent the damage situation of elements or regions in a structural system. Unlike many papers in the literature that test damage detection methods only in numerical examples or simple experimental tests, this work also assesses the presented method in a real structure showing that it has potential for applications in real practical situations. Three different cases are evaluated through the methodology: numerical simulations, an experimental lab structure, and a real bridge. Initially, a cantilever beam and a 10-bar truss were numerically analyzed under ambient vibrations with different damage scenarios and noise levels. Afterward, the method is assessed in an experimental beam structure and in the Z24 bridge benchmark. The numerical simulations showed that the methodology is promising for identifying, locating, and quantifying single and multiple damages in a single stage, even with noise in the acceleration signals and changes in the first vibration mode of 0.015%. In addition, the Z24 bridge study confirmed that the damage detection method can localize damage in real civil structures considering only natural frequencies in the input factors, despite a mean difference of 4.08% between the frequencies in the healthy and damaged conditions. [ABSTRACT FROM AUTHOR]

Compared with most dynamic tests, point load test is widely used in engineering practice because of its wide requirements for test conditions. In offshore mining engineering, the surrounding rock is affected by dynamic load impact and corrosion of various aqueous solutions for a long time. Therefore, it is of great significance to study the influence of hydrochemical corrosion on dynamic mechanical properties of rock to ensure the stability of surrounding rock. In this paper, a large number of dynamic point load and dynamic uniaxial compression tests were carried out on the granite mined from a large mine by using the Split Hopkinson pressure bar test device after the corrosion of pH values of 2, 5, and 7 solutions, respectively. Based on the energy theory, the crushing energy consumption in the test process is analyzed, and finally the fitting formula of the dynamic compressive strength and the crushing energy consumption in the dynamic point load test is obtained through fitting analysis. The results show that when the crushing energy consumption in the dynamic point load test is used to estimate the dynamic compressive strength, a certain crushing energy consumption (the final value of this test is 70 J in this paper) is more accurate, and it can estimate the dynamic compressive strength under various corrosion conditions under this crushing energy consumption. However, with the change of crushing energy consumption in the dynamic point load test, this transformation relationship is no longer accurate, and it is necessary to modify this transformation relationship with corrosion condition as the influencing factor. This conclusion can provide reference for obtaining the dynamic compressive strength of rocks under different corrosion conditions in engineering field in the future. [ABSTRACT FROM AUTHOR]

Research on evaluating highway bridge performance through vehicle-bridge interaction (VBI) analysis has made significant advancements. However, when assessing driving comfort, using vehicle acceleration instead of human acceleration poses challenges in accurately representing comfort. First, the paper proposes a finite element analysis method for human-vehicle-bridge spatial interactions (HVBSIs). Then, the importance of wheel path roughness difference is explored when assessing driving comfort. Furthermore, a new method for evaluating driving comfort that includes human and vehicle vibration responses has been proposed, and a simulation example of the steel-concrete composite beam bridge (SCCBB) is used to verify the effectiveness of the proposed method. The results demonstrate that the HVBSI analysis method effectively simulates the interconnected vibrations of the human body, the spatial vehicle model, and the three-dimensional (3D) bridge model. Differences in wheel path roughness significantly impact the roll vehicle vibration responses, which are crucial in driving comfort analysis. The driver's body vibration response is essential for evaluating driving comfort, and its inclusion leads to increased comfort indices values. In comparison to traditional methods, the overall vibration total value (OVTV) increases by a maximum of 109.04%, and the level of weighted vibration ( L e q ) increases by a maximum of 6.74%. This leads to an upgrade from grade IV to grade V in terms of comfort level, indicating a reduced comfort. [ABSTRACT FROM AUTHOR]

A structured dynamic overlapping grid and a user-defined function are used to study the projectile launching process, and the hybrid Roe scheme is used to solve the flow field with strong shock wave. The launching process of a projectile with a muzzle decompression device is numerically simulated by using a three-dimensional transient model, and the flow field inside the muzzle decompression device and the development process of the muzzle flow field in the projectile launching process are discussed in detail. Compared with no device, the muzzle decompression device can effectively reduce the peak pressure around the muzzle; the numerical results are in agreement with the corresponding experimental values. The numerical investigation in this paper is helpful to understand the mechanism of pressure reduction of the device. It also provides a new way to reduce the muzzle pressure of aircraft gun. [ABSTRACT FROM AUTHOR]

The amplitude modulation method was used to generate a non-Gaussian road profile with prescribed power spectral density (PSD) and kurtosis. The vehicle vibration fatigue damage potential has been proven to be closely related to the amplitude modulation signal (AMS) and kurtosis of vehicle response. In this paper, the iterative method of AMS modelling based on absolute standard Gaussian distribution is first reviewed. To address the long iteration time problem, a closed-form formulation is presented to construct the AMS directly. Furthermore, by proving that the vehicle response under a slowly varying non-Gaussian road profile excitation can be regarded as the product of the same AMS and vehicle response under a Gaussian road profile excitation with the same PSD, the theoretical relationship between fatigue damage spectrum (FDS) of vehicle response under non-Gaussian and corresponding Gaussian road profiles is formulated based on the AMS. A case study is used to verify the proposed approach. The results show that a wide range of specified kurtosis of road profile can be achieved and the kurtosis of vehicle response is the same as for the road profile. Given kurtosis and fatigue exponent, the extra fatigue damage caused by non-Gaussian road profile can be derived easily from the corresponding Gaussian road profile without calculating the vehicle response, which lays the foundation for a significantly simplified and more accurate fatigue test of vehicle vibration under non-Gaussian road profile. [ABSTRACT FROM AUTHOR]

The impact-rubbing dynamic characteristics of the power turbine rotor with the hollow shaft and offset discs for aircraft engine are investigated, and the impact-rubbing analytical method for the complex rotor based on MDOP Timoshenko beam theory is proposed in this paper. Compared with the traditional approach, the novel method can obtain more data to satisfy the need of engineering. The Lagrange equation is adopted to derive the equations of motion for the rotor system, and the Newmark-β method is applied to solve the equations. The diagrams such as the bifurcation, axis trajectory, spectrum, and Poincaré map are obtained to research on the effect of the rotating speed, gap, and eccentricity on the vibration response. The finite element analysis was carried out to validate the correctness of the theoretical modeling method. The research results indicate that the power turbine rotor with the hollow shaft on operation shows the various nonlinear dynamic behaviors including the multiperiod, quasi-period, jumping phenomenon, and chaotic motions; there exists an optimal gap between the rotor and the stator from the perspective of the efficiency and the dynamics; the optimal gap should make system avoid the resulting chaos or the quasi-period motion for the stability and safety of the machinery. [ABSTRACT FROM AUTHOR]

In this paper, the vehicle ISD (inerter-spring-damper) suspension and power-driven-damper control strategy are combined to the suspension design, and the power-driven-damper semiactive ISD suspension is proposed. The dynamic models of the passive suspension S1 and two semiactive ISD suspensions S2 and S3 are established. Based on the port-controlled Hamiltonian theory, the power-driven-damper semiactive control strategy is designed by analyzing the power transfer of suspension S3. Then, the parameters of the two models are optimized by the particle swarm optimization algorithm, and the optimization results show that the suspension S3 has better performance. The influence of the semiactive damping coefficient, the spring stiffness, and the inertance on the vibration suppression performance is investigated based on the suspension S3. The effect of parameter perturbation on power-driven-damper semiactive vehicle ISD suspension illustrates that the designed semiactive vehicle ISD suspension has better ride comfort in a wider range frequency and good robust performance. [ABSTRACT FROM AUTHOR]

This paper introduces a novel type of floating machine gun that can be simplified as a self-balancing two-degree-of-freedom mechanical system with distinct vibration characteristics. The model accounts for intricate motion patterns and encompasses numerous potential influencing factors. Multifactor combination optimization of the system represents a pressing engineering challenge. After establishing a simulation model for the machine gun and validating it experimentally, seven factors were chosen as optimization variables. The maximum recoil displacement of the inner receiver (MRD) and the firing rate were chosen to be indicators. Orthogonal combinations and variance analyses were used, and the effects of multiple factors were analyzed using SPSS software; these processes led to a determination of the optimal combination. The results indicated that the piston cylinder pressure, the bi-directional buffer spring energy storage, and the inner receiver mass significantly affected the MRD. Furthermore, the automaton mass and the reset spring energy storage were found to substantially affect the firing rate. Careful analysis of the variance results facilitated the determination of the optimal combination of parameter values. Remarkably, the optimal combination chosen resulted in an MRD reduction of approximately 20.2% and a firing rate increase of approximately 26.6%. [ABSTRACT FROM AUTHOR]

A ship equipment pedestal is a structure that connects power equipment to a hull. It must have a high load-bearing capacity and the ability to withstand large impact loads. In this paper, a novel structure with a positive-negative Poisson's ratio is proposed. The deformation mechanism and mode of this structure under quasistatic compression loading are analysed via numerical simulation. Based on this new structure, a multicellular pedestal is designed, and its bearing capacity and impact resistance are analysed. The structural parameters of the pedestal are optimized. An experiment is conducted to evaluate the impact resistance of the pedestal model, which confirms that the proposed multicellular pedestal exhibits excellent impact resistance. [ABSTRACT FROM AUTHOR]

The stable operation of the process industrial system, which is integrated with various complex equipment, is the premise of production, which requires the condition monitoring and diagnosis of the system. Recently, the continuous development of deep learning (DL) has promoted the research of intelligent diagnosis in process industry systems, and the sensor system layout has provided sufficient data foundation for this task. However, these DL-driven approaches have had some shortcomings: (1) the output signals of heterogeneous sensing systems existing in process industry systems are often high-dimensional coupled and (2) the fault diagnosis model built from pure data lacks systematic process knowledge, resulting in inaccurate fitting. To solve these problems, a graph feature fusion-driven fault diagnosis of complex process industry systems is proposed in this paper. First, according to the system's prior knowledge and data characteristics, the original multisource heterogeneous data are divided into two categories. On this basis, the two kinds of data are converted to physical space graphs (PSG) and process knowledge graphs (PKG), respectively, according to the physical space layout and reaction mechanism of the system. Second, the node features and system spatial features of the subgraphs are extracted by the graph convolutional neural network at the same time, and the fault representation information of the subgraph is mined. Finally, the attention mechanism is used to fuse the learned subgraph features getting the global-graph representation for fault diagnosis. Two publicly available process chemistry datasets validate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In response to the high-noise, nonlinear, and nonstationary characteristics of vibration signals from aircraft environmental control system (ECS) turbofan rolling bearings, this paper proposes a diagnostic method for the degree of ECS turbofan bearing faults based on the Hidden Markov Model (HMM). Experimental results demonstrate that HMM can accurately diagnose and predict faults in ECS turbofan rolling bearings. The HMM method enhances diagnostic accuracy, and its effectiveness and feasibility in fault diagnosis based on different rolling bearing fault instances are elaborated. By employing the HMM model to establish precise models from decomposed dynamic data, it successfully identifies faults such as the fracture of the bearing cage under biased load conditions, although its performance in recognizing overheating faults is suboptimal. [ABSTRACT FROM AUTHOR]

Virtual track trains are a new type of rail transportation because the multisection formation structure leads to more degrees of freedom of the vehicle, which may cause unstable phenomena, such as tailing, cross-swing, and folding, affecting the stability and ride comfort of the vehicle driving. To explore the effect of damping coefficient of the articulated systems on vehicle dynamics performance, a vehicle system dynamics model is established based on the actual parameters of a three-module six-axle virtual track train. According to ISO14791: 2000, select typical working conditions such as straight line, lane change, and 1/4 circle curve, and optimize the damping coefficient of the articulated systems through co-simulation. The study shows that under straight-line conditions, increasing the damping coefficient can effectively suppress the yaw angular acceleration and improve the lateral ride comfort of the vehicle but has little effect on the vertical ride comfort. Under lane change conditions, too large or small damping coefficients will deteriorate the train's lateral stability, and a reasonable damping coefficient will improve the yaw damping ratio of the vehicle and reduce the lateral sway vibration between vehicles. Under the 1/4 circle curve conditions, the additional articulated system damper will reduce the vehicle's curve passing performance. In this paper, the articulation stability of multimodule fully connected vehicles is analyzed and optimized for the first time, and the damping coefficient control strategy is given based on the geometric tracking control method. The research results are of great significance for the parameter selection of virtual track trains' articulated system and the design and development of specialized articulated systems for related vehicles. [ABSTRACT FROM AUTHOR]

When the thickness of a structure is reduced to decrease weight, it may experience structural vibration and disturbance. The use of passive patches is effective in addressing this issue when the loss factor is small or when space and weight are restricted. The greatest attenuation occurs when passive patches are used across the entire coverage area. However, passive patches of reasonable size must be affixed to ensure that they are effective in terms of cost and design. In this paper, the sum of squares' value for the bending mode shape is used to determine the location of a small passive patch to achieve vibration damping for multiple modes. Under the condition of forced vibration, the modal contribution of each mode is obtained. Using this contribution as a weight, the optimal position of the passive patch is determined as the maximum value obtained in the form of a linear combination multiplied by the curvature of the beam. Simulation and experiment were used to test the efficacy of the location determined for passive patches. It was determined that, depending on the location of the passive patch, the peak amplitude at the natural frequency of each mode decreased significantly, validating the effectiveness of the design method. [ABSTRACT FROM AUTHOR]

Deep learning has recently received extensive attention in the field of rolling-bearing fault diagnosis owing to its powerful feature expression capability. With the help of deep learning, we can fully extract the deep features hidden in the data, significantly improving the accuracy and efficiency of fault diagnosis. Despite this progress, deep learning still faces two outstanding problems. (1) Each layer uses the same convolution kernel to extract features, making it difficult to adaptively select convolution kernels based on the features of the input image, which limits the network's adaptability to different input features and leads to weak feature extraction. (2) Large number of parameters and long training time. To solve the above problems, this paper proposes an integrated deep neural network that combines an improved selective kernel network (SKNet) with an enhanced Inception-ResNet-v2, named SIR-CNN. First, based on the SKNet, a new three-branch SKNet was designed. Second, the new SKNet is embedded into a depthwise separable convolution network such that the model can adaptively select convolution kernels of different sizes during training. Furthermore, the convolution structure in the Inception-ResNet-v2 network was replaced by the improved depthwise separable convolution network to achieve effective feature extraction. Finally, the time-frequency maps of the raw vibration signals are obtained through short-time Fourier transform (STFT) and then sent to the proposed SIR-CNN network for experiments. The experimental results show that the proposed SIR-CNN achieves superior performance compared to other methods. [ABSTRACT FROM AUTHOR]

Tooth flank fracture (TFF) and tooth interior fatigue fracture (TIFF) usually occur on case-harden gears in electromechanical coupling systems, both starting from the core caused by metal fatigue. The cracks propagate rapidly compared with the total life of a gear, so that it is necessary to detect and identify the faults in time when they take place in order to avoid danger. In this paper, the time-varying mesh stiffness model of two types of faults is established by the potential energy method and validating by the finite element method. Based on the stiffness model, the influence of faults on the electromechanical system and their fault characteristics are analyzed, which provides a theoretical basis for the health detection of electromechanical coupling systems. The results indicate that in the early stage of the three faults, i.e., tooth root fracture, tooth interior fatigue fracture, and tooth flank fracture, it is hard to discriminate the faults. But after the second stage, the faults can be distinguished by the vibration amplitude, frequency band components, and phase diagrams. The TFF can be discerned into different stages by frequency domains and phase diagrams. When the fracture occurs completely, three faults can be easily distinguished by the time domain and phase diagram. In the frequency domain, the TRF can also be distinguished from the other two faults by referring to the sideband component near the meshing frequency. [ABSTRACT FROM AUTHOR]

In order to broaden the muffler frequency band in the low-frequency range of the exhaust muffler and to achieve the purpose of broadband noise reduction, in this paper, a model of an annular connecting pipe muffler is proposed using the finite element method (FEM) to simulate the nonreflection boundary condition and to solve the transmission loss (TL). In addition, the experimental value is obtained by the spatial five-point measurement method and compared with the simulated value, and the validity and reliability of the solution model are verified. Compared with a simple expansion muffler, the average TL of the annular connecting pipe muffler is increased by 11.86 dB, and the maximum TL is increased by 18.31 dB, effectively widening the muffler frequency area, and the overall performance is effectively improved. Finally, the influence of structural factors is analyzed, including the width (W) of the annular connecting pipe, the length (L) of the annular connecting pipe, and the length ratio (m) of the front and rear chambers on the TL and on the width of the anechoic frequency band. The results reveal that the width and length of the annular connecting pipe and front-to-back cavity length ratio are the most significant factors to influence the TL, muffler frequency band, and elimination or reduction of the passing frequency, respectively. [ABSTRACT FROM AUTHOR]

Using a monopile foundation due to a reliable and simple technology has a wide application in engineering structures. This paper investigates numerically the performance of an offshore wind turbine with a monopile foundation equipped with a restriction plate at a middle inside height of the monopile under the wind, wave, and seismic loadings. Different parameters, including wind velocity, wave period, wave height, soil characteristics, and combination of loadings, are considered in nonlinear finite element dynamic analyses. Results are given in terms of the distribution of displacement and bending moment over the turbine height and frequencies. The results reveal that by increasing the wind velocity, the responses of the tower increase, and the wind load acting on the hub has the most important effect on the turbine behavior rather than the wind load acting on the tower body. Furthermore, the values of maximum displacement and bending moment under wind and wave loading decrease with the increase of the shear strength of the soil, whereas the responses of the tower under earthquake loading increase. Generally, it is necessary to consider the effect of a combination of wind, wave, and earthquake loadings on the design of the turbine tower. [ABSTRACT FROM AUTHOR]

When high-speed trains operate under braking conditions, the wheel-rail interaction increases significantly, which can lead to more serious wear problems. To analyze the evolution of wheel wear and the dynamic characteristics of wheel-rail under braking conditions, this paper first carries out long-term monitoring of the service state of wheel-rail during the operation period. The study analyzed the matching characteristics of the measured wheel-rail profile and calibrated the wear model by using the collected data. The resulting wear prediction model was then used to examine the wheel wear characteristics under braking conditions. The research results indicate that during the operation period, the wheel experiences tread concave wear within a range of ±20 mm of the rolling circle, at a rate of approximately 0.05 mm per 10,000 km. Meanwhile, the rail experiences top surface wear at a natural rate of about 0.09 mm per year. Concave wear causes the contact point of the wheel-rail to appear in two zones, resulting in a sudden change of contact geometric parameters. The concave worn wheel and rail with a 60 N profile have better matching compared to the 60 rail profile. Increasing the braking torque and wheel-rail friction coefficient will significantly increase the wheel wear depth on straight sections. On small-radius curve sections, rail side lubrication can significantly reduce high rail side wheel flange wear. A worn concave wheel can lead to unfavorable wheel-rail contact geometry characteristics and increase low-frequency components in the vehicle's lateral dynamic response. [ABSTRACT FROM AUTHOR]

It is essential for realizing the most suitable product buffer packaging design to quantify the vibration transmission characteristics of the product packaging system. The experiment system for the vibration transmission path of protective packaging is designed in this paper. The practical system is used to analyze the vibration transfer path of the product packaging system and identify the critical transfer path. The concepts of the cushions' contribution rate and the cushions' weighted contribution rate are introduced. The product cushioning based on the weighted equal contribution rate of the cushions is proposed. It has been verified by experiments that the system can accurately identify the transfer path with the weighted contribution rate of the cushions as a reference for the design of product buffer packaging, which improves the utilization rate of buffer packaging materials and reduces the cost of packaging materials. The weighted equal contribution rates of buffer pads 1, 2, 3, and 4 are 40%, 27%, 22%, and 11%, respectively. For the needs of experiment teaching, the teaching content based on the protective packaging transfer path testing system is designed, which provides a reference for the practical education of the packaging specialty. [ABSTRACT FROM AUTHOR]

For the air-to-air missile warhead, there is a cabin with a certain thickness at a distance around the fragments. At present, the influence of missile cabin has not yet been taken into account in the study of fragment velocity. In this paper, based on the law of conservation of energy, the theoretical equation of fragment velocity considering the kinetic energy of cabin debris was deduced. Then, the rationality of the theoretical formula is validated through the static explosion experiments of two prototype warheads, one with a titanium alloy cabin and the other without any cabin. It was found that after the warhead is equipped with the cabin, part of the energy is consumed to drive the cabin debris, resulting in a decrease in fragment velocity, but the velocity of cabin debris was greater than that of fragment of warheads without any cabin. Besides, through numerical simulation, the driving process of fragments and cabin debris during explosive detonation loading of the warhead with the cabin was studied, which can be divided into six stages, and the error between numerical result and experimental value is not more than 4.8%. Finally, the variety regulation of fragment velocity and cabin debris velocity at different interval distances was further studied by numerical simulation. The results indicate that fragment velocity of warheads with cabin at different interval distances is basically the same, but cabin debris velocity decreases with the increase of interval distance. This conclusion can provide a reference for the structural design and fragment velocity evaluation of warheads with cabin. [ABSTRACT FROM AUTHOR]

Based on the engineering background of shield construction of a subway section in Chongqing, which needs to pass through a park and there is a lake inside this park, this paper adopts theoretical analysis methods and numerical simulation calculation methods to explore the distribution law of the seepage field and the characteristics of water pressure in lining segments during shield tunneling. The results show that, during the whole excavation of a double-track tunnel with EPB shield, the maximum vertical effective stress is about 4.24 MPa, which is located at the arch foot of the tunnel. The maximum effective stress in the horizontal direction is about 3.61 MPa, which is located on both side walls of the tunnel in the horizontal direction; after the left and right tunnels are excavated in sequence, a "double precipitation funnel-shaped" pore pressure distribution is formed around the tunnel; during the construction of the shield tunnel, the vertical displacement and horizontal displacement of the surrounding rock show an increasing trend and gradually tend to be stable values of 24.09 mm and 25.28 mm; the segment vault has settlement, the maximum settlement is 21.8 mm, the arch bottom has uplift, and the maximum uplift is 24.4 mm. The maximum horizontal displacement of the segment appears on both sides of the arch waist, and the maximum horizontal displacement decreases with the increase of excavation steps; the positive bending moment of the lining segment is mainly distributed on both sides of the arch crown, and the negative bending moment is mainly distributed on both sides of the arch bottom. The axial force of the lining segment is compressive stress, and the maximum axial force is mainly distributed on both sides of the arch waist. The maximum normal shear stress occurs on both sides of the segment arch bottom. The study conclusions provide theoretical foundation and a new guidance for long-term safety evaluation of underwater tunnel structures. [ABSTRACT FROM AUTHOR]

The space shafting is the core component of the momentum exchange attitude control actuator for spacecraft.The dynamic behavior of space shafting has an important impact on the performance of the actuators. Based on the dynamic theory of rolling bearing, this paper presents a dynamic analysis model of space shafting for the interaction between bearing balls and oil-containing nonmetallic cage under combined loads. Also, the accuracy of the analysis model was verified through a high-speed camera system to conduct a cage speed test. In addition, the dynamic behavior of balls and cage under combined loads and the interaction between them is also analysed. The results show that the axial displacements of balls fluctuate periodically under combined loads, and the rotation speeds of balls and cage are easily affected by the load, presenting as the oscillation of speed. Also, the force between balls and cage increases as the load increases. The dynamic behavior of balls and cage could be effectively improved by avoiding excessive torque loads and limiting the axial preload to 40 N. The wear failure caused by unstable operation of bearings cannot be ignored. This model is more practical in completing simulation analysis of different operating conditions and structural parameters of the shafting system. It provides a theoretical reference for the structural design and performance analysis of space shafting. [ABSTRACT FROM AUTHOR]

The popularity of new structural systems and prestressing technology has led to the widespread use of the large-space floor structures in large buildings such as high-speed rail terminals, conference centers, and sports stadiums. The reduction of nonessential load-bearing elements and the increase in span of the structure result in a reduction in the natural frequency and damping ratio of the floor structure, while the floor is a crowded area with disorderly flow between people, which may lead to human-induced vibration problems. In order to assess the dynamic performance of the large-span floor structure under crowd load, the random crowd-floor vertical interaction equation is derived, and the correctness of the equation is verified by comparing it with the test. For the stochastic nature of walking crowds, a formulation modeling method for random crowd is proposed, including pedestrian-dynamics parameters, formulation model, and response parameters. The model is characterized by considering inter- and intrasubject variability and reflects the vertical interaction between pedestrians and the floor system. According to the random crowd-floor dynamic equation, the variation of modal parameters and acceleration response of the floor during random crowd walking are also analyzed. The research in this paper will help in analyzing the comfort of large-span floor structures under pedestrian excitation and better meet the needs of the development of lightweight large-span structures. [ABSTRACT FROM AUTHOR]

The frequency- and temperature-dependent characteristics of viscoelastic materials significantly affect the vibration response of the damped composite structures. In this paper, an efficient strategy of hybrid expansion combined with dynamic reduction is developed to solve the steady-state response of the frequency- and temperature-dependent viscoelastic structure characterized by nonproportional system, and the sensitivity analysis is carried out based on the adjoint variable method. The similarity index is defined to distinguish the correlation among different design layouts. Two instances demonstrated the validity of the proposed approach. The findings indicated that a positive compromise between accuracy and efficiency can be achieved, and the computational time can be significantly reduced while ensuring the accuracy of the results. Furthermore, it has been discovered that the excitation frequency and temperature significantly impact the optimal configuration of damping material. The effects of layer thicknesses and volume fractions on optimization designs are also further investigated. [ABSTRACT FROM AUTHOR]

In this paper, the instantaneous rock burst test of Beishan granite is carried out by using a deep rock burst simulation test system and an acoustic emission monitoring system. The acoustic emission data were monitored in real time during the test. The variation of the number and energy of acoustic emission events was studied, and the distribution characteristics of rock burst debris were analyzed. Based on plate and shell mechanics, the failure process of surrounding rock is discussed from the perspective of structural stability. The results show that (1) when the vertical stress reaches 171.31 MPa, the specimen is destroyed and the number of acoustic emission events and cumulative absolute energy before the specimen is destroyed increase sharply. (2) The debris generated by rock burst is mainly composed of slab debris, flaky debris, and thin flaky debris, accounting for 93.53% of the total debris. (3) When the length or height of the rock slab is constant, the maximum tensile stress in the rock slab decreases nonlinearly with the increase of rock slab thickness. For the same size of the rock slab, the farther away from the roadway wall, the greater the maximum tensile stress in the rock slab. (4) When the thickness of the rock slab is constant, the maximum tensile stress in the rock slab increases nonlinearly with the increase of height to thickness ratio K. When the ratio of height to thickness K is constant, the maximum tensile stress in the rock slab increases with the increase of rock slab thickness h. (5) With the increase of covering depth, the critical failure thickness of the rock slab decreases nonlinearly and the surplus energy increases nonlinearly. [ABSTRACT FROM AUTHOR]

Whole-body vibration (WBV) is a significant concern for vehicle users as it can negatively impact their health and comfort. As such, effective vibration isolation is critical in vehicle suspension design. The ability of a vehicle suspension to isolate vibrations depends primarily on the suspension design and the type of springs used. One type of spring that has proven advantageous for vibration isolation is the air spring. Air springs can vary frequencies and adjust their stiffness in response to different loading conditions, making them ideal for meeting both suspension load-carrying and occupants' comfort requirements. Pneumatic (air) suspension has been in use in the automotive industry for several decades and has undergone significant advancements during this period. This paper presents a systematic review of pneumatic suspension since its inception. The review highlights different air spring modeling techniques, types of pneumatic suspension, and control methods. The study also discusses the functional flexibility of pneumatic suspension, its ability to offer a wide range of control options to drivers, and its broad application in almost all ranges of vehicles, including chassis, cabin, and seat suspension systems. In addition, this paper presents a summary of the pros and cons of pneumatic suspension and suggests future research directions. The advantages of pneumatic suspension include effective vibration isolation, improved ride comfort, and the ability to adjust suspension stiffness and ride height. On the other hand, the disadvantages include higher cost and complexity compared to other types of suspension. Overall, the findings of this review demonstrate that pneumatic suspension is a viable solution for vehicle suspension design, particularly in situations where vibration isolation and ride comfort are critical. [ABSTRACT FROM AUTHOR]

The failures of steel guides can excite complex and intense transverse oscillations of hoisting containers in the mine hoisting process. The present paper mainly contributes to reveal the response characteristics of the transverse oscillations of mine conveyances excited by various faults such as interface misalignment, local bulge, orbital gap, bending deformation, and orbital tilt. First, a rigid-flexible coupled virtual prototype model between the conveyance and the steel guide was established. Subsequently, the vibration response characteristics of the container under various single and coupling excitations were simulated and analyzed. Eventually, a new type of roller cage shoe with a magnetorheological damper was put forward to decrease the transverse impact responses. Based on the hyperbolic tangent model of magnetorheological dampers, a semiactive fuzzy PID method was studied to explore the vibration suppression of the container. The results showed the fuzzy PID method can play a good role in the vibration reduction. This paper can give a fine scheme for the virtual simulation and semiactive vibration control of the mine hoisting system. [ABSTRACT FROM AUTHOR]

The aim of this study is to compose a corotational finite element formulation for space frames with geometrically nonlinear behavior under dynamic loads. Using a moving frame through three successive rotations similar to Euler angles is one of the oldest techniques; however, there are still some gaps that require attention, mainly due to singularity. Hence, alternative techniques had been developed, sometimes elusive and computationally expensive. In this paper, we went back to the old technique and filled the gaps. Three-coordinate systems are used, i.e., the fixed global coordinate system, the fixed local coordinate system that is attached individually to every element, and the corotational local frame for each element that moves and rotates with the element. The deformation is always small relative to the corotational frame. The successive rotations between different coordinate systems are expressed using Tait–Bryan angles. Lagrange's equation is used to derive the equation of motion, and the stiffness and mass matrices are obtained using the Euler–Bernoulli beam model. A MATLAB code is developed based on the Newton–Raphson method and the Newmark direct integration implicit method. In traditional techniques, singularity is attained when any rotation angle in the fixed local frame approaches π / 2 , and if any is greater than π / 2 , the techniques could fail to specify the location of the element. In this paper, each case is treated with a proper procedure, and special handling of trigonometric formulations prevents singularity and correctly specifies the location of elements in all situations. Different examples of beams and frames are analysed. While the method is not intricate, it is timesaving, is highly effective, provides more stable and robust analysis, and gives sufficiently accurate results. Compared to the parametrization of the finite rotations technique, the method has a significant reduction in the convergence rate because it avoids the storage of joint orientation matrices. [ABSTRACT FROM AUTHOR]

To solve the problems of dynamic model parameter perturbation and external disturbances during the operation of the ball screw meta-action unit, an adaptive sliding mode control method based on disturbance compensation and inertia identification is proposed in this paper. First, a model of the ball screw meta-action unit is established and the dynamic equation is derived. Taking into account the uncertainty of the dynamic parameters, a least squares method with a forgetting factor is introduced to identify the moment of inertia in real time, and the identification results are utilized to adaptively adjust the sliding mode control law. Second, a nonlinear disturbance observer is designed to effectively observe the load disturbance, and the observed value is substituted into the sliding mode control as feedforward compensation to improve the anti-interference ability of the controller. Committed to the chattering of traditional sliding mode control, an improved adaptive exponential sliding mode reaching law is exploited to construct a novel sliding mode controller, thereby suppressing the slid mode chattering more thoroughly. Finally, the superiority of the proposed method is verified by MATLAB/Simulink simulation and compared with the other two control methods; the control method proposed in this paper can effectively improve the tracking performance of the system and has good robustness. [ABSTRACT FROM AUTHOR]

In this paper, a vehicle-bridge coupling dynamic model is established considering the vertical wheel-rail tight contact and the lateral simplified wheel-rail creeping. Through the site test and the numerical calculation, the dynamic deflections and the stresses of the U-shaped girder in the Nanjing S6 Urban Rail Transit in China are obtained, and the effectiveness of the established numerical model is verified. By changing the vehicle types and speeds, the dynamic amplification coefficients (DAFs) of the vertical deflections and the biaxial stresses at the girder bottom including the key points at the plate and section intersections are calculated. The research shows that the distribution of the lateral stresses is more complex than that of the deflection and the longitudinal stresses. Based on the calculation results considering various vehicle types, it is suggested that the DAFs of the vertical deflections and the longitudinal stresses are taken as 1.30, and the DAF of the lateral stresses remains at 1.40 as stipulated by the code. The research of this paper is to provide a reference for the structural design and size optimization of the U-shaped girders for urban rail transit. [ABSTRACT FROM AUTHOR]

Fault diagnosis is an important means to ensure the safe and reliable operation of mechanical equipment. In machinery fault diagnosis, collecting and mining the potential fault information of the vibration signal is the most commonly used method to reflect the operating status of the equipment. In engineering scenarios, in the face of rotating machinery with variable speed, simple time domain analysis or frequency domain analysis is difficult to solve the problem. The time-frequency analysis technology that combines time-frequency transformation and data analysis can solve practical engineering problems by capturing the transient information of the signal. At present, a large number of related literatures have been published in academic journals. This paper hopes to provide convenience for relevant researchers and motivate researchers to further explore by summarizing the published literature. First, this paper briefly explains the concept of time-frequency analysis and its development. Then, the time-frequency transformation method proposed for the characteristics of rotating machinery fault vibration signal and related works of literature are reviewed, and the key issues of the application of time-frequency transformation method in rotating machinery fault diagnosis are discussed. Next, this paper summarizes the relevant literature on the combination of data analysis technology and time-frequency transformation and sorts out its development route and prospects. The study reveals that time-frequency analysis technology is able to detect the rotating machinery fault effectively. The time-frequency analysis technology has made abundant achievements in the field of rotating machinery fault diagnosis. It is expected that this review would inspire researchers to explore the potential of time-frequency analysis as well as to develop advanced research in this field. [ABSTRACT FROM AUTHOR]

The measurement of helicopter rotor blade structural load amid flight has always been the difficulty in flight test. In this paper, the principle of the existing blade structural load measurement method (electrical measurement method) was analyzed, and the problem of physical decoupling in the use of this method was expounded. As a weak signal measurement, the electrical measurement method also has electromagnetic interference problems, which will affect the flight test period of blade structural load measurement. Therefore, a numerical decoupling measurement method based on fiber Bragg grating (FBG) was proposed. Then, the new method was applied and verified in the load equation modeling test and the flight test under the real atmospheric environment was carried out. Through comparing and analyzing the measured data of the new method and the electrical measurement one, the correctness of the FBG data decoupling method was validated. The results indicate that the method proposed in this paper can effectively improve the efficiency of blade load equation modeling engineering and has good application value. [ABSTRACT FROM AUTHOR]

Modal mass is one of the modal parameters that are required to define the dynamic behavior of a structure when a modal model is used. In experimental modal analysis (EMA), modal masses are the least reliable modal parameter, while in operational modal analysis (OMA), modal masses cannot be estimated because the exciting forces are not measured. In this paper, the concept of cross-length between mode shapes is formulated for continuous and discrete systems, and important properties are derived from this definition. It is demonstrated that the cross-length is zero for all modes in constant mass density systems. For structures consisting of parts with different mass density, equations that relate the partial cross-lengths over the different volumes and the total masses of the different parts can be formulated for each mode, i.e., there is a relationship between the cross-length and the total mass of the parts with different mass density. The equations proposed in the paper have been validated through numerical simulations and experimental testing on two lab-scaled structures. This methodology can also be applied as a correlation technique, specifically to determine how the mass is distributed in the structure, as well as a technique to construct a proportional FRF in constant mass density systems. [ABSTRACT FROM AUTHOR]

This paper presents the development of a numerical model able to track in time the behavior of nonlinear focused ultrasound when interacting with tiny gas bubbles in a liquid. Our goal here is to analyze the frequency components of the waves by developing a model that can easily be adapted to the geometrical restrictions and complexities that come out in several application frameworks (sonochemistry, medicine, and engineering). We thus model the behavior of nonlinear focused ultrasound propagating in a liquid with gas bubbles by means of the finite-element method in an axisymmetric three-dimensional domain and the generalized- α method in the time domain. The model solves a differential system derived for the nonlinear interaction of acoustic waves and gas bubble oscillations. The high nonlinearity and dispersion of the bubbly medium hugely affect the behavior of the finite-amplitude waves. These characteristics are used here to generate frequency components of the signals that do not exist at the source through nonlinear mixing (parametric antenna). The ability of the model to work with complex geometries, which is the main advantage of the method, is illustrated through the simulation of nonlinear focused ultrasound in a medium excited from two spherical sources in opposite directions. [ABSTRACT FROM AUTHOR]

The topography and the incident angle of seismic waves both have considerable effects on the seismic ground motions of canyons in a half-space. In this paper, the theory of wavefield decomposition and the artificial boundary is used to develop a method for inputting obliquely incident SV waves. Formulas for the equivalent nodal forces applied to the truncated boundary are derived and implemented in the finite element method. The validity of the proposed method is verified by a test case. A parametric study is then performed to investigate the influence of canyon geometry and incident angle of SV waves on the seismic response of trapezoidal canyons. The numerical results indicate that the canyon inclination has a more significant effect on the ground motion amplification than its height and width. The amplification effects are strongly related to the canyon inclination and the incident angle of SV waves. Additionally, the dominant frequency corresponding to the acceleration of the canyon crests is not sensitive to the incident angle of SV waves. [ABSTRACT FROM AUTHOR]

This paper presents a thermal transfer model and optimization of a V-beam dimension to improve the critical frequency fC (i.e., expanding the effective working frequency range) of an electrothermal V-shaped actuator (EVA). The obtained results are based on applying the finite difference model, a method for calculating the critical frequency, as well as conditions to ensure the mechanical stability and thermal safety of EVA. The influence of beam dimensions (i.e., length L, width w , and incline angle θ of the beam) on the variation of critical frequency fC is investigated and evaluated. Moreover, the particle swarm optimization (PSO) algorithm is used to figure out the optimal beam dimensions aiming to increase the critical frequency while satisfying conditions such as mechanical stability, thermal safety, and suitable displacement of EVA. With the optimal dimensions of V-beam (L = 679 µm, w = 4 µm, and θ = 1.8°), the critical frequency of the V-shaped actuator can be achieved up to 136.22 Hz at a voltage of 32 V (average increment of fC is 33.1% with the driving voltage changing from 16 V to 32 V) in comparison with the nonoptimal structure (fC is only 102.34 Hz at 32 V). [ABSTRACT FROM AUTHOR]

Blasting vibration generated from blasting excavation of subway tunnel may endanger the adjacent structures buried in strata. To guarantee their safety and stability, it is crucial to understand the spatial variation law of blasting vibration in strata. In this paper, the blasting excavation of the large cross-sectional tunnel of Wuhan Metro Line 8 is studied. Three-dimensional finite element simulation is performed using the dynamic finite element program LS-DYNA, and its validity is verified by the field monitoring data. The spatial variation law of blasting vibration in layered strata is investigated through analyzed the distribution characteristic of blasting vibration in three directions, including the direction along the axis of the large cross-sectional tunnel, the direction perpendicular to the axis of the large cross-sectional tunnel, and the direction along the depth. A prediction model for blasting vibration velocity, which considers the impact of elevation differences, is established through dimensional analysis, enabling the prediction of blasting-induced vibrations at various depths in the layered strata. [ABSTRACT FROM AUTHOR]

Xinzhuang Coal Mine is a typical kilometer-deep rockburst mine in the Ningzheng mining area of China Huaneng Group, which is still in the capital construction period. At present, there are a few studies on the rockburst mechanism and prevention of this mine. In order to explore the occurrence mechanism and main influencing factors of rockburst under the complex geological conditions of large buried depth, thick topsoil, and hard overburden in Xinzhuang Coal Mine, this paper, based on the analysis of the basic geological data of the mine, deeply explores the comprehensive disaster factors of Xinzhuang Coal Mine; then, uses the analytic hierarchy process to carry out quantitative analysis of each disaster factor, and finally, it obtains the impact type and occurrence mechanism of the mine. Through research, it is found that the main disaster factors of Xinzhuang Coal Mine are mining depth, coal seam thickness, coal seam thickness change, tectonic stress field, hard overburden, roadway layout, bottom coal reservation, and tunneling activities. The key to the process of the rockburst disaster in Xinzhuang Coal Mine is the superimposed effect of static and dynamic loads on the roadway surrounding the rock system. The potential rockburst type during excavation and mining is the "high static and dynamic load disturbance" type. [ABSTRACT FROM AUTHOR]

Large temperature differences exist between the winter and summer seasons in different regions of China. Such temperature differences, caused by seasonal changes, may affect the life cycles of piles. Under natural conditions, such as long-term operation under the ambient environment and loads, piles and the surrounding soil undergo peel damage. To study such peel damage between the pile and soil at different temperatures, we installed concrete test piles in soil and subjected them to different temperatures. A crack with a width of 2 cm, depth of 10 cm, and damage range of 90° was applied at the side of the piles. Furthermore, a horizontal impact load was applied near the top of the pile and a piezoelectric ceramic sensor was used to obtain the stress wave response signals. The experimental results reveal that with a decrease in the soil temperature, the amplitude and fluctuation range of the signals received by the piezoelectric sensor decreased. According to the experimental results, in the group with the greatest influence of temperature, keeping other conditions unchanged and setting different crack depths, the horizontal impact load can also be introduced to observe the frequency change. It can be observed that the larger the crack depth, the smaller the frequency. Finally, ABAQUS was used for simulations, whose results were found to be consistent with those of the experiments. This paper describes a method for determining the safety of soil and piles with peel damage at different temperatures, and it also provides a validation of the necessity of holding the rest constant. [ABSTRACT FROM AUTHOR]