Search Results (33,349)

Background/Objectives: The quadratus lumborum (QL) muscle is a key structure involved in patients with low back pain (LBP). Since the discriminative capability of morphological descriptors is uncertain and considering the high prevalence of myofascial trigger points and the poor reliability of manual palpation in this condition, developing a reliable procedure for assessing the QL’s tenderness is needed for facilitating the diagnosis and monitoring changes over time. We aimed to analyze the intra- and inter-examiner reliability of SWE for calculating the QL tenderness in patients with LBP. Methods: Using a convex transducer, longitudinal shear wave elastography (SWE) images of the QL muscle were acquired bilaterally twice in 52 volunteers with moderate LBP and disability by one experienced examiner and one novel examiner to measure shear wave speed and Young’s modulus as stiffness metrics. Results: Intra-examiner reliability estimates demonstrated high consistency independently of the examiner’s experience (intraclass correlation coefficients (ICCs) > 0.930) for both metrics. However, experienced examiners showed smaller minimal detectable changes. Additionally, inter-examiner reliability was lower, with ICCs ranging from 0.57 to 0.68, and significant differences in mean values between examiners (p < 0.01) were found. Conclusions: This procedure exhibited excellent intra-examiner reliability for assessing QL muscle stiffness in patients suffering LBP, indicating high repeatability of measurements when performed by the same examiner. In addition, experienced examiners demonstrated greater sensitivity in detecting real changes not attributed to measurement errors. However, inter-examiner reliability was moderate, highlighting the need for consistent examiner use to avoid measurement variability and averaging multiple measurements to enhance the accuracy. Full article

A hybrid computational framework integrating the finite volume method (FVM) and finite difference method (FDM) is developed to solve two-dimensional, time-dependent nonlinear coupled Boussinesq-type equations (NCBTEs) based on Nwogu’s depth-integrated formulation. This approach models nonlinear dispersive wave forces acting on a stationary vessel and incorporates a frequency dispersion term to represent ship-wave generation due to a localized moving pressure disturbance. The computational domain is divided into two distinct regions: an inner domain surrounding the ship and an outer domain representing wave propagation. The inner domain is governed by the three-dimensional Laplace equation, accounting for the region beneath the ship and the confined space between the ship’s right side and a vertical quay wall. Conversely, the outer domain follows Nwogu’s 2D depth-integrated NCBTEs to describe water wave dynamics. Interface conditions are applied to ensure continuity by enforcing the conservation of volume flux and surface elevation matching between the two regions. The accuracy of this coupled numerical scheme is verified through convergence analysis, and its validity is established by comparing the simulation results with prior studies. Numerical experiments demonstrate the model’s capability to capture wave responses to simplified pressure disturbances and simulate wave propagation over intricate bathymetry. This computational framework offers an efficient and robust tool for analyzing nonlinear wave interactions with stationary ships or harbor structures. The methodology is specifically applied to examine the response of moored vessels to incident waves within Paradip Port, Odisha, India. Full article

Binaural audio is crucial for creating immersive auditory experiences. However, due to the high cost and technical complexity of capturing binaural audio in real-world environments, there has been increasing interest in synthesizing binaural audio from monaural sources. In this paper, we propose a two-stage framework for binaural audio synthesis. Specifically, monaural audio is initially transformed into a preliminary binaural signal, and the shared common portion across the left and right channels, as well as the distinct differential portion in each channel, are extracted. Subsequently, the POS-ORI self-attention module (POSA) is introduced to integrate spatial information of the sound sources and capture their motion. Based on this representation, the common and differential components are separately reconstructed. The gated-convolutional fusion module (GCFM) is then employed to combine the reconstructed components and generate the final binaural audio. Experimental results demonstrate that the proposed method can accurately synthesize binaural audio and achieves state-of-the-art performance in phase estimation (Phase-l2: 0.789, Wave-l2: 0.147, Amplitude-l2: 0.036). Full article

This study explores the design and analysis of a negative stiffness plate aimed at enhancing vibration suppression. The concept of the negative stiffness plate is illustrated through the implementation of periodic resonators embedded within a host plate, each incorporating a single vibration absorber. These absorbers generate shear forces and efficiently capture vibration energy when excited resonantly. To validate the effectiveness of these negative stiffness composite plates, numerical experiments were conducted. The findings reveal that the damping of the absorber can significantly influence the frequency stopband created by the absorber’s resonance. Notably, damping has a minor but positive effect on broadening the stopband width and reducing the overall vibration response of the host plate. Furthermore, this study highlights the potential application of negative stiffness plates in mitigating elastic waves induced by earthquakes. Full article

River surfing has evolved from natural rivers to artificial standing waves, like the Fuchslochwelle in Nuremberg, where optimizing wave quality and safety remains a challenge. Key issues include recirculation zones that pose risks, particularly at higher inflows. This study addresses safety and performance improvements by introducing geometric modifications to reduce recirculation zones. Using STAR-CCM+ simulations, 16 configurations of baffles and inlays were analyzed. A 3D-CAD model of the Fuchslochwelle was developed to test symmetrical and asymmetrical configurations, focusing on reducing vorticity. Results showed that baffles placed 2 m from the inlay reduced recirculation zones by over 50%. Asymmetrical setups, combining wall and inlay baffles, also proved effective. Following simulations, a baffle was installed at 3 m, enhancing safety and quality. Previously, inflows above 7.5 m³/s caused dangerous backflow, requiring surfers to swim or dive to escape turbulence. With the baffle, safe operation increased to 9 m³/s, a 20% improvement, making the system suitable for surfers of all skill levels. These finding provide a novel approach to enhancing flow dynamics, applicable to a wide range of artificial standing waves. The valuable insights gained enable operators to optimize the dynamics and accessibility through geometric modifications while ensuring safety for users. Full article

Radome stealth technology is a key research area in aircraft stealth design. Traditional aircraft stealth methods primarily focus on optimizing the shape to scatter radar waves and using absorbing materials to absorb radar waves. However, when these methods are applied to radomes, they can negatively impact antenna performance. By combining Frequency-Selective Surface (FSS) technology with radome design, it is possible to ensure good transmission performance for the antenna within its operating frequency range while simultaneously reducing the radar cross-section outside the operating frequency range, achieving an integrated design for both transmission and stealth. This paper outlines the technical approaches for radome stealth, reviews the research status of scattering stealth radomes and absorbing stealth radomes based on FSS both domestically and internationally, and provides an outlook on the future development of FSS radomes from the perspectives of omnidirectional broadband, conformal design, and intelligent control. Full article

Compression via pressure waves is an effective but specific way of compressing gases. This paper presents a broad overview of work related to the use of unsteady processes in the construction of micro-engines. The main advantages of wave rotors, such as a low rotor speed, self-cooling channels, high compression in a single stage, and the possibility of operating at a very small geometric scale, are addressed, and their disadvantages, such as the requirement of the precise synchronization of wave processes and poor torque-generation properties, are also outlined. This review highlights the possibility of operating at a geometric scale, which conventional solutions have failed to achieve. In the thermodynamic cycle of a micro-engine, a compression process carried out in an unsteady manner is superior in efficiency to stationary solutions. On the contrary, in the expansion process, fluid inertia is an obstacle to the full utilization of the thermal energy transferred to the fluid in the combustion chamber. The best solution is, therefore, a favorable combination of both features, leading to unsteady compression and steady-state expansion in the heat engine cycle. This article presents an overview of the existing technical solutions and published research results devoted to the construction of pressure wave compression micro-engines: patents, scientific publications describing various research methods, numerical calculations, and the experimental results of unusual technical solutions. Characteristic solutions and problems arising in the development of these methods, which range from superchargers to autonomous engines, are presented and discussed. Directions for further research are suggested. Full article

In this study, a hybrid heading control framework for unmanned surface vehicles (USVs) is proposed, combining variable domain fuzzy Proportional–Integral–Derivative (VUF-PID) with an improved algorithmic Beetle Antennae Search–Particle Swarm Optimization–Simulated Annealing (BAS-PSO-SA) optimization to address the multi-objective control challenge. Key innovations include a self-tuning VUF mechanism that improves disturbance rejection by 42%, a weighted adaptive optimization strategy that reduces parameter tuning iterations by 37%, and an asymmetric learning factor that balances global exploration and local refinement. Benchmarks using Rastrigin, Griewank, and Sphere functions show superior convergence and 68% stability improvement. Ocean heading simulations of a 7.02 m unmanned surface vehicle (USV) using the Nomoto model show a 91.7% reduction in stabilization time, a 0.9% reduction in overshoot, and a 30% reduction in optimization iterations. The experimental validation under wind and wave disturbances shows that the heading deviation is less than 0.0392°, meeting the IMO MSC.1/Circ.1580 standard, and an 89.5% improvement in energy efficiency. Although the processing time is 12.7% longer compared to the GRO approach, this framework lays a solid foundation for ship autonomy systems, and future enhancements will focus on MPC-based time delay compensation and Field-Programmable Gate Array (FPGA) acceleration. Full article

Shipborne high-frequency surface wave radar (HFSWR) can extend the measurement area due to the flexible movement of the platform and provide a new way to monitor large-area marine environment parameters. It has already been applied to wind and current measurements. However, extracting significant wave height using shipborne HFSWR presents challenges due to the complex effects of platform motion on the Doppler spectrum, which invalidate onshore methods. To address this, a novel method for extracting significant wave height from the spreading first-order Bragg peaks of shipborne HFSWR with a single antenna is proposed, which is immune to inevitable antenna pattern distortion and especially suitable for the space-constrained shipborne HFSWR. The method sequentially estimates wind directions, spreading parameters, and wind speeds from Bragg peaks and develops a new relationship between significant wave height and wind speed to enable wave height extraction. Additionally, a preprocessing step is introduced to mitigate the impact of noise and discretization errors. Simulations and field experiments validate the feasibility and accuracy of the method across various scenarios, with a detection range of up to 120 km without auxiliary measurements. Comparisons between the radar-extracted and fifth-generation European Centre for Medium-Range Weather Forecasts reanalysis (ERA5) or buoy-measured results demonstrate consistency. Full article

When the XBeach model is used to simulate beach profiles, the selection of four sensitive parameters—facua, gammax, eps, and gamma—is crucial. Among these, the two key parameters, facua and gamma, are particularly sensitive. However, the XBeach model does not specify the exact choice of these four key parameters, offering only a broad range for each one. In this paper, we investigate the applicability of tuning these four parameters within the XBeach model. We employ Generalized Likelihood Uncertainty Estimation (GLUE) to optimize the model settings. The Brier Skill Score (BSS) for each parameter combination is calculated to quantify the likelihood probability distribution of each parameter. The optimal parameter set (facua = 0.20, gamma = 0.50) was ultimately determined. Here, the facua parameter represents the degree of influence of wave skewness and asymmetry on the direction of sediment transport, while the gamma parameter represents the equivalent random wave in the wave dissipation model and is used to calculate the probability of wave breaking. Six profiles of the southern beach on Chudao Island are selected to validate the results, establishing the XBeach model based on profile measurement data before and after Typhoon “Lekima”. The results indicate that after parameter optimization, the simulation accuracy of XBeach is significantly improved, with the BSS increasing from 0.3 and 0.17 to 0.68 and 0.79 in P1 and P6 profiles, respectively. This paper provides a recommended range for parameter values for future research. Full article

Installing offshore wind jackets faces increasing risks from dynamic marine conditions and is challenged by trajectory deviations due to coupled hydrodynamic and environmental factors. To address the limitations of software, such as long simulation times and tedious parameter adjustments, this study develops a rapid prediction model combining Radial Basis Function (RBF) and Backpropagation (BP) neural networks. The model is enhanced by incorporating both numerical simulation data and real-world measurement data from the launching operation. The real-world data, including the barge attitude before launching, jacket weight distribution, and actual environmental conditions, are used to refine the model and guide the development of a fully parameterized adaptive controller. This controller adjusts in real time, with its performance validated against simulation results. A case study from the Pearl River Mouth Basin was conducted, where datasets—capturing termination time, six-degrees-of-freedom motion data for the barge and jacket, and actual environmental conditions—were collected and integrated into the RBF and BP models. Numerical models also revealed that wind and wave conditions significantly affected lateral displacement and rollover risks, with certain directions leading to heightened operational challenges. On the other hand, operations under more stable environmental conditions were found to be safer, although precautions were still necessary under strong environmental loads to prevent collisions between the jacket and the barge. This approach successfully reduces weather-dependent operational delays and structural load peaks. Hydrodynamic analysis highlights the importance of directional strategies in minimizing environmental impacts. The model’s efficiency, requiring a fraction of the time compared to traditional methods, makes it suitable for real-time applications. Overall, this method provides a scalable solution to enhance the resilience of marine operations in renewable energy projects, offering both computational efficiency and high predictive accuracy. Full article

Low-frequency seismic vibrations extremely limit the performance of ground simulation facilities for space-borne gravitational wave detections, which need to be substantially suppressed. Active vibration systems are thus required. However, the tilt-translation coupling of inertial sensors strongly limits the performance of vibration isolation platforms in the low frequency range, which requires a precise measurement of the low-frequency tilt signal. This study compares two methods for the tilt signal measurement: the differential-mode method and the direct method. The differential-mode method estimates tilt signals by analyzing differential motion between two inertial sensors, while the direct method utilizes an interferometric tilt sensor (ITS) which consists of a suspended rotational beam system and an interferometer for the readout. Experimental results show that ITS achieves a lower noise floor. Its noise floor is dominated by the thermal-mechanical noise below 0.25 Hz and the readout noise of the interferometer above 0.25 Hz. The findings highlight the potential of ITS for improving the performance of vibration isolation platforms in the low-frequency range. Full article

The heterogeneous integration of ferroelectric thin films on silicon- or silicon nitride-based platforms for photonic integrated circuits plays a crucial role in the development of nanophotonic thin film modulators. For this purpose, an ultrathin seed film was recently introduced as an integration method for ferroelectric thin films such as BaTiO₃ and Pb(Zr,Ti)O₃. One issue with this self-orienting seed film is that for non-planarized circuits, it fails to act as a template film for the thin films. To circumvent this problem, we propose a method of planarization without the need for wafer-scale chemical mechanical polishing by using hydrogen silsesquioxane as a precursor to forming amorphous silica, in order to create an oxide cladding similar to the thermal oxide often present on silicon-based platforms. Additionally, this oxide cladding is compatible with the high annealing temperatures usually required for the deposition of these novel ferroelectric thin films (600–800 °C). The thickness of this silica film can be controlled through a dry etch process, giving rise to a versatile platform for integrating nanophotonic thin film modulators on a wider variety of substrates. Using this method, we successfully demonstrate a hybrid BaTiO₃-Si ring modulator with a high Pockels coefficient of rwg=155.57±10.91 pm V⁻¹ and a half-wave voltage-length product of VπL=2.638±0.084 V cm, confirming the integration of ferroelectric thin films on an initially non-planar substrate. Full article

Background: Social isolation is linked to survival and health. However, dietary effects of social activities, and gender differences, over time are unknown. Methods: A prospective study of adults (45+y) reporting daily fruit or vegetable (F/V) intake (at wave 1) from the Canadian Longitudinal Study on Aging (CLSA). Multivariable mixed logistic regression assessed changes in social isolation or breadth of social participation (wave 1 to 2) in relation to adverse changes in F/V (non-daily intake) at wave 3 in women and men. Results: Women who remained socially isolated between waves 1 and 2 had 85% higher odds of non-daily vegetable intake (OR 1.85 [95% CI: 1.32, 2.59]) and over twofold higher odds of non-daily fruit intake (2.23 [1.58, 3.14]), compared to reference (not isolated at waves 1 and 2). Higher odds of non-daily F/V intake were also observed for women who changed from isolated at wave 1 to not isolated at wave 2. Women and men who had less diverse social participation at waves 1 and 2 had 28–64% higher odds of non-daily F/V intake, compared to their counterparts with diverse social participation at both waves. Higher odds of non-daily fruit were also seen for women who had diverse social participation at wave 1 but reduced their diversity at wave 2 (1.35 [1.12, 1.62]). Conclusions: Results showed persistent social isolation impacted changes in F/V among women only, while limited breadth of social participation affected F/V intake in both genders. Further longitudinal research on the complexities of social engagement and eating behavior is warranted. Full article

This work develops a novel two-dimensional, depth-integrated, non-hydrostatic model for wave propagation simulation using a weighted average non-hydrostatic pressure profile. The model is constructed by modifying an existing non-hydrostatic discontinuous/continuous Galerkin finite-element model with a linear, vertical, non-hydrostatic pressure profile. Using a weighted average linear/quadratic non-hydrostatic pressure profile has been shown to increase the performance of earlier models. The results suggest that implementing a weighted average non-hydrostatic pressure profile, in conjunction with a calculated or optimized Ө weight parameter, improves the dispersion characteristics of depth-integrated, non-hydrostatic models in shallow and intermediate water depths. A series of analytical solutions and data from previous laboratory experiments verify and validate the model. Full article