Search Results (1,129)

The present study investigates the influence of geometric parameters on the vibro-acoustic performance of piezoelectric speakers, with the objective of establishing quantitative design guidelines for resonance tuning and sound pressure level (SPL) enhancement. Understanding the dimension-dependent behavior of such devices is essential for the development of compact and efficient acoustic transducers. To this end, a fully coupled electromechanical–acoustic finite element model is developed in the frequency domain, incorporating linear piezoelectric constitutive relations, structural dynamics, and an external acoustic air domain. The model systematically examines the effects of variations in piezoelectric disc thickness, brass diaphragm thickness, and diaphragm radius. The results demonstrate that increasing the piezoelectric disc thickness leads to a noticeable increase in resonance frequency and a measurable enhancement in SPL due to strengthened electromechanical coupling. In contrast, reducing the brass membrane thickness primarily shifts the resonance frequency to lower values, while producing negligible changes in SPL amplitude. Furthermore, enlarging the diaphragm radius significantly decreases the fundamental resonance frequency, confirming its dominant influence on stiffness-controlled vibration behavior. These findings quantitatively establish the relationship between geometric design parameters and acoustic response, providing a predictive framework for performance optimization. The proposed modeling approach offers an effective and reliable tool for the design and refinement of high-performance piezoelectric speaker systems. Full article

Objectives: This study aimed to demonstrate the feasibility of a novel wireless energy-transmitting implantable diaphragm pacemaker for restoring respiratory ventilation. Methods: The diaphragm pacing (DP) system was designed based on the principle of electromagnetic resonance coupling. The safety of device implantation was analyzed through finite-element simulations of multi-field coupling between electromagnetic heating and biological tissue. In vitro testing with coils embedded in pork demonstrated the system output characteristics. This device was used in miniature Bama pigs that underwent deep anesthesia and respiratory arrest (N = 8). Respiratory airflow, diaphragmatic displacement, and blood gases were used to evaluate the effectiveness of the designed DP system. Results: Thermal effect simulation results show that the temperature rise of the surrounding tissue does not exceed 2 °C during 1 h of transmission power (0.5–1.3 W) operation of the receiver. In vitro tests with two receivers embedded in pork showed that the DP system can effectively output stimulation waveforms over a certain transmission distance (5–35 mm). The stimulation waveform output by the receiver is consistent with the parameters set by the external controller. In phrenic nerve electrical stimulation experiments, the peak respiratory airflow and tidal volume remained stable over 50 consecutive respiratory cycles. The tidal volume (108.63 mL) and diaphragmatic displacement (0.883–2.15 cm) in a pig induced by DP demonstrate the effectiveness of respiratory ventilation. The arterial blood gas analysis results and temperature rise experiment during implantation further confirmed the effectiveness and safety of the ventilation. Conclusions: The implantable diaphragmatic pacemaker developed in this study exhibits good thermal safety, stable output, and effective respiratory ventilation. A control group with commercial diaphragmatic pacemakers and data from chronic implantation experiments are needed to further evaluate its effectiveness. Full article

As a composite structure with both support and load-bearing functions, the composite underground structure wall has been widely applied in engineering. However, in terms of scientific research, a simplified calculation method that can reflect the internal force distribution law and the interaction mechanism between the two walls has not been found. In terms of design applications, the internal force calculated by the traditional total method has a relatively large deviation from the actual situation. This study proposes an internal force calculation method for composite underground structure walls based on the incremental method. The difference between the at-rest earth–water pressure and the active earth–water pressure is taken as the load increment, which is applied step-by-step according to the construction conditions. Based on the Wangsheren Subway Station in Jinan, China, the actual bending moments of the diaphragm wall and inner lining wall are back-analysis using Plaxis 2D V20 with measured horizontal deformation as input. Models of the incremental method and total method are built in Midas GEN 2022. Bending moment distributions under various conditions are compared. The results show the following: (1) The absolute values of the bending moments of the two walls calculated by the incremental method are inversely proportional along the depth direction, which is consistent with the trend of back-analysis, while the absolute values of the bending moments of the two walls calculated by the total method are directly proportional. (2) The incremental method has a higher calculation accuracy for the characteristic points of the bending moment. In terms of calculated values, the bending moment of the diaphragm wall is 0.87–1.90 times that of the back-analysis, and that of the inner lining wall is 1.06–4.93 times, while the deviation of the total method is significantly larger (0.47–3.34 times for the diaphragm wall and 1.49–16.64 times for the inner lining wall). (3) Under complex working conditions, the calculation results of the incremental method are still better than those of the total method. This incremental method can better simulate the interaction mechanism and the internal force redistribution characteristics of the composite underground structure wall. The calculation results are more in line with the engineering reality, which can save materials while ensuring the structural safety and provides a more scientific theoretical method for relevant designs. Full article

This study addresses the high-risk scenario of dual-sided deep foundation pit construction adjacent to operational metro lines, a complex urban underground engineering context with significant safety implications. A multi-level dynamic safety risk assessment model is proposed by integrating the Analytic Hierarchy Process (AHP) with a risk matrix. Existing approaches generally lack the capability to dynamically incorporate spatiotemporal variations and real-time construction management information, limiting their applicability under complex working conditions. To overcome these limitations, the Tianjin Shouchuang Beiyunhe Metro Complex project is adopted as a case study to develop a concise and efficient risk assessment framework. The framework introduces spatiotemporal effect and safety management coefficients to dynamically adjust risk values and conducts risk identification and integrated evaluation across four dimensions—geology, environment, design, and construction—using 25 indicators. The model enables quantitative, real-time identification and dynamic control of safety risks during metro foundation pit construction. The assessment results indicate that the overall project risk is classified as Level I (highest), with the western pit exhibiting slightly higher risk. Targeted mitigation measures include the use of diaphragm walls with internal buttresses and grouting reinforcement. Compared with conventional methods, the proposed model demonstrates significant advantages in adapting to dynamic construction conditions, enhancing engineering applicability, and strengthening early-warning capability. These improvements provide a scientific, practical, and scalable technical solution for the accurate identification of critical risks and proactive safety management in complex metro foundation pit projects. Full article

To investigate the fatigue performance of a novel green low-carbon steel–AAUHPC (Alkali Activated Ultra-high Performance Concrete, AAUHPC) composite bridge deck and achieve its structural optimization, this paper proposes a steel–AAUHPC composite bridge deck structure featuring double-sided welding of U-shaped ribs. Firstly, the numerical model of a symmetrical composite bridge deck is established by ABAQUS finite element software. The stress response of key fatigue structural details is analyzed, and the fatigue life is evaluated based on the S-N curve method. At the same time, the calculation results are compared with the orthotropic steel bridge deck and the steel–UHPC composite bridge deck. Secondly, the CCD method and RSM method are used to construct a mathematical regression model with the structural weight W per unit area and the fatigue stress amplitude of key details as the target. Finally, NSGA-III is used to optimize structural parameters such as AAUHPC thickness, top plate thickness, diaphragm thickness and spacing to obtain the Pareto-optimal solution set. The results show that the AAUHPC material has both environmental protection and excellent mechanical properties, and its compressive and splitting tensile strength is significantly higher than that of ordinary concrete, which is close to the UHPC level. The steel–AAUHPC composite bridge deck can significantly improve the fatigue performance of the orthotropic steel bridge deck. After laying the AAUHPC layer, the stress amplitude of each fatigue detail decreases, and the C1 detail decreases by up to 69.4%. Except for the C6 detail, the rest of the structural details meet the infinite-life design criteria, and the overall improvement effect is comparable to that of the steel–UHPC composite bridge deck. The constructed response surface model has good prediction accuracy. The optimization results show that the fatigue stress amplitude and the structural weight W are mutually restricted. Among the 15 sets of Pareto-optimal solutions obtained, solution U8 achieves weight minimization under the premise of satisfying the infinite-fatigue-life criterion. The optimal parameter combination is: AAUHPC thickness of 40 mm, top plate thickness of 10 mm, diaphragm thickness of 16 mm, and diaphragm spacing of 2400 mm. The research results can provide a theoretical basis for the fatigue design and engineering application of a new green steel–AAUHPC composite bridge deck. Full article

The deep foundation pit excavation of subway will cause horizontal displacement, uneven settlement and other adverse effects on the adjacent shield. The use of servo steel strut has a certain effect on deflection correction, but the current understanding of the influencing factors of deflection correction is not comprehensive. Based on structural and spatial symmetry, the influence of tunnel depth, tunnel and foundation pit clear distance and deformation control quantity of enclosure structure on deflection correction quantity was studied by symmetrically designed model test and numerical simulation, and the prediction formula of deflection correction quantity considering tunnel and foundation pit clear distance and deformation control quantity of enclosure structure was proposed. The results show that with an increase in the tunnel’s burial depth, deflection correction decreases significantly. When the tunnel is near the foundation pit bottom, there is no significant correction effect, and the control law of the tunnel ground pressure under the servo steel strut loading is consistent with the correction law. Deflection correction is negatively correlated with the tunnel and foundation pit clear distance, and positively correlated with the deformation control of the diaphragm wall. The curve of the deformation control of the enclosure structure and the deflection correction is parabolic. The deflection correction is an exponential function of the ratio of the deformation control of the enclosure structure to the clear distance between the tunnel and the foundation pit, and the servo deflection correction follows a normal distribution along the longitudinal axis of the tunnel, showing obvious symmetry characteristics in the foundation pit influence zone. Full article

With the increasing functional and geometric complexity of modern steel buildings, irregular beam-to-column joints are becoming increasingly common in engineering practice, while their seismic performance and force transfer mechanisms remain insufficiently understood. Based on previous full-scale cyclic loading tests on unequal-depth steel beam (UDSB) and staggered steel beam (SSB) joints incorporating inclined internal diaphragms, this study presents numerical simulations and parametric analyses of irregular steel beam to concrete-filled steel tube (CFST) column joints. Three-dimensional nonlinear finite element models were developed using ABAQUS and validated against experimental results. The strengthening effects of internal diaphragms and concrete infill were then comparatively investigated. The results indicate that internal diaphragms increase the initial stiffness and load-carrying capacity of the joints to approximately 2.0–2.3 times and 1.16–1.8 times, respectively, compared with joints without diaphragms, whereas concrete infill provides smaller enhancements of about 1.3 times in stiffness and 1.2–1.3 times in strength. In addition, the hysteretic response of joints without diaphragms shows good agreement with the post-fracture behavior observed in the experiments, validating the diaphragm fracture mechanism. A parametric study further demonstrates that, under cyclic loading, the beam depth ratio, staggered floor ratio, column wall thickness, column width, diaphragm thickness, and diaphragm opening diameter have significant influences on joint strength and stress distribution, while the effect of axial load ratio is relatively minor. Finally, a strength prediction method applicable to inclined-diaphragm UDSB and SSB joints is proposed, and corresponding fitted expressions are derived based on the parametric results. The findings provide useful guidance for the seismic design of irregular steel beam–CFST column joints incorporating internal diaphragms. Full article

Background: The breathing cycle consists of abdominal breathing (AB), for which the diaphragm is responsible, and thoracic breathing (TB), generated by the intercostal muscles. Contraction of the two portions of the diaphragm accounts for 80% percent of inspiration. While bilateral diaphragmatic paralysis causes severe shortness of breath, hemidiaphragm paralysis (HDP) gives fewer symptoms at rest, making it difficult to recognize and diagnose. Because this condition is rare, little is known regarding its consequences on breathing efficiency. Hypothesis: Based on previous studies, we hypothesized that body positions substantially affect the efficiency of breathing in a patient with unilateral hemidiaphragm paralysis and the corresponding physiological parameters. Aims: To measure and compare the amplitudes of abdominal and chest movements in different body positions in an individual with HDP and measure parameters indicating breathing efficiency. Patient and Methods: The patient had HDP due to iatrogenic phrenic nerve injury. Changes in the circumference of the abdomen and chest were measured during inhalation and exhalation with respiratory plethysmography belts (placed on standardized reproducible positions on the chest and abdomen) in different body positions: sitting (SI), standing (ST), lying (SU) and prone (PR). Breathing frequency was calculated, and blood oxygen saturation (SpO₂) was measured with a pulse oximeter. Results: The percentage (%) contributions of abdominal breathing were SI: 16.0; ST: 50.3; SU: −53.5; PR: 1.1. A negative sign shows paradoxical breathing. Blood oxygen saturation (SpO₂) in the four positions was SI: 93%; ST: 93%; SU: 82%; and PR: 82%, whereas the respiratory rate (1/min) was SI:19.4; ST: 15.0; SU: 37.5; PR: 35.9. Conclusions: Body position markedly influences the relative contributions of abdominal and thoracic breathing and overall respiratory efficiency in patients with hemidiaphragm paralysis; abdominal breathing in the supine and prone positions is greatly reduced leading to decreased blood oxygen saturation, a compensatory increase in respiratory rate, and severe dyspnea even at rest. Full article

The design and main parameters of a plasma–chemical reactor containing two compartments are presented. One compartment houses a vacuum-arc evaporator, while the other houses a planar magnetron. The compartments are separated by a diaphragm with a dosing slot for injecting copper vapor into the TiN synthesis compartment. The conditions for the synthesis of superhard TiN-Cu composite coatings are experimentally determined. Based on established process parameters for TiN synthesis in a nitrogen-containing plasma by Ti evaporation using a vacuum-arc discharge, it is proposed to apply TiN-Cu coatings by injecting Cu vapor into the TiN synthesis area and sputtering Cu using a magnetron discharge. XRD analyses of both TiN and TiN-Cu coatings show the presence of WC, Ti₂C, and TiN. EDS analysis confirms 5.57 at. % copper on the surface of the TiN-Cu coating. Real-life operating tests of TiN-Cu coatings on replaceable WC-TiC-Co (79/15/6 wt.%) alloy hexagonal inserts used for cutting 40Kh steel revealed that applying the TiN-Cu coating extends the tool life of WC-TiC-Co inserts by about 2.5 times compared with uncoated tools. Cutting force measurements on TiN-Cu-coated inserts showed no vibration or noise during cutting, driven by a reduced friction coefficient and improved heat dissipation at the contact zone between the cutting edge and the workpiece, thereby lowering the temperature in that area. Full article

In order to study the stability of orthotropic steel box girders and the characteristics of the synergistic stress mechanism of key components, the test method of axial compression using the scale model of steel box girder segments was carried out, and the collaborative working performance of the plate ribs of the U-shaped stiffener plate and the influence mechanism of the diaphragm on the structural stability were systematically studied. The results show that the strain difference between the deckplate and the U rib increases significantly with the increase in load, and the distribution law of the end chamber is larger than the middle, and the bottom plate is larger than the top plate and the web plate. The diaphragm mainly bears the tensile force under axial load, which provides out-of-plane restraint for the stiffener, and its restraint effect is the strongest at the web plate and the weakest at the bottom plate. This paper clarifies the synergistic stress mechanism of U-rib stiffeners under high axial pressure conditions, quantifies the contribution of diaphragms to local stability, and provides a theoretical basis for the structural design of similar bridges. Full article

This study addresses the critical need for sustainable energy by optimizing diaphragm-type piezoelectric elements for efficient waste vibration energy harvesting. Traditional experimental optimization of complex, non-linear design parameters including applied load, tapper diameter, and support structures is often resource-intensive and time-consuming. To overcome these limitations, we developed a novel hybrid machine learning framework that seamlessly integrates an Artificial Neural Network (ANN) with a Modified Grey Wolf Optimization (mGWO) algorithm. The ANN was rigorously trained on experimental data using Bayesian Regularization, establishing itself as a robust and high-fidelity surrogate model capable of accurately predicting voltage output based on diverse input parameters, evidenced by an R-value close to 1. This predictive model subsequently served as the fitness function for the mGWO algorithm, which incorporated a non-linear control parameter to efficiently explore the multi-dimensional design space and effectively balance exploration with exploitation. The framework successfully identified the optimal configuration for maximizing voltage output, predicting a theoretical maximum of approximately 70.67 V. This optimal setup notably involved a high applied load of 100 N, the 6CA multi-pointed tapper configuration, and the three-support boundary condition, which is consistent with the experimentally validated results. The computational findings demonstrated excellent agreement with empirical results while providing significantly higher resolution for design insights. This validated, predictive tool offers a substantial advancement for the future scaling and design optimization of piezoelectric energy harvesters, minimizing the need for extensive physical prototyping and ensuring efficient stress transfer without mechanical failure. Full article

A perineal hernia in dogs results from a failure of the pelvic diaphragm and is often accompanied by a displacement of the pelvic and abdominal organs. However, detailed descriptions of accompanying vascular and neural alterations are limited. This study uses a combination of fluoroscopic imaging and anatomical dissection to characterize the perineal arterial and neural anatomy in two control dogs and three dogs with unilateral or bilateral perineal hernias; however, only one control underwent fluoroscopy, and neural dissection was performed on one control and on the bilateral case. In the control specimen, the vascular pattern followed the classical NAV arrangement. In contrast, the hernia cases exhibited marked variability, including altered origins and lengths of the dorsal and ventral perineal arteries; long- or short-type internal iliac and internal pudendal arteries; and displacement or deterioration of the superficial perineal nerve. These changes were most pronounced in the dog with a bilateral hernia, which was accompanied by severe degeneration of the levator ani and coccygeus muscles and herniation of the colon, urinary bladder, and urethra. Fluoroscopic findings closely corresponded with anatomical observations, demonstrating the value of imaging in the preoperative assessment of vascular variations. Overall, this study provides a comprehensive description of the neurovascular and muscular modifications associated with perineal hernias and emphasizes the need for individualized anatomical evaluations to optimize surgical planning and reduce intraoperative risks. Full article

Timber frame diaphragms play a central role in the lateral stability of modern timber buildings, yet current design codes insufficiently capture their nonlinear behaviour and governing failure mechanisms. This study evaluates two finite element modelling strategies to improve the prediction of diaphragm response. The first strategy, implemented in MATLAB^®, explicitly models the nonlinear behaviour of sheathing-to-framing (STF) connections using an oriented orthogonal multilinear damage law. Validation against experimental tests on partially anchored and fully anchored diaphragms as well as in-plane bending specimens demonstrated accurate predictions of stiffness and force–displacement behaviour in both the linear-elastic and elastoplastic ranges. Deviations in peak load predictions for the detailed model reached up to approximately 25%, while stiffness predictions remained within approximately 10% of the experimental values. The second approach, implemented in commercial structural engineering software, represents STF connections by uncoupled elastoplastic spring elements. Although post-peak softening cannot be captured, peak capacities were predicted within approximately 3–5% for several configurations, with reliable stiffness estimates in most cases. A quantitative comparison using the normalised root mean square error between experimental and numerical force-displacement curves yielded values between approximately 5% and 14%, indicating good agreement between the numerical predictions and the experimental behaviour. Overall, the detailed model enables high-fidelity nonlinear analysis and insight into failure mechanisms, whereas the simplified spring approach offers a practical and computationally efficient modelling strategy suitable for routine engineering design. Full article

Accurate absolute pressure measurement is of great importance in industrial control, environmental monitoring, and aerospace. Traditional fiber-optic Fabry–Perot (F-P) pressure sensors usually involve complex microfabrication and high-cost demodulation systems, while conventional diaphragm capsule sensors are limited in sensitivity and resolution. This work presents a low-cost, high-resolution fiber-optic F-P absolute pressure sensor. The sensor uses a vacuum capsule as one reflective surface and a partially reflective fiber collimator as the other, forming a low-finesse F-P interferometer. The cavity length is linearly modulated by the elastic deformation of the capsule under pressure, and high-precision demodulation is realized using frequency modulated continuous wave (FMCW) interferometry instead of conventional spectral methods. Static experiments from 10 to 110 kPa show that the sensor exhibits a high sensitivity of 15,105 nm/kPa and a resolution of 3.3 Pa. Furthermore, the sensor operates normally within the range of −20 °C to 70 °C, exhibiting a pressure–temperature cross-sensitivity of 0.081 kPa/°C and a cavity length drift of 496 nm/h. With the advantages of high performance, simple structure, low cost, and good scalability by selecting different capsules, the proposed sensor has promising potential for practical applications in pressure measurement fields. Full article

This paper presents the results of a study of the dynamic performance of an aerostatic thrust bearing with a microgroove and simple diaphragms. The objective of this study was to determine the influence of the lubrication gap thickness and the volume of the microgroove and pockets on the structural dynamics. Unlike most studies that typically use the second-order harmonic oscillator equation as the characteristic equation, the root criteria are determined with high accuracy when the characteristic equation is of an order no lower than the fourth order. The presented formulas allow one to find the optimal calculated dimensional gap, microgroove and pocket volume in terms of the best dynamic performance. For a well-damped thrust bearing, the required response speed and sufficient stability margin can only be achieved within a narrow range of 1–2 times the bearing gap volume. Calculations have shown that to ensure satisfactory thrust bearing dynamics, the calculated gap should not exceed 10–15 µm. Full article