Search Results (1,145)

Aiming at the problem that complex underwater environments induce outliers in Doppler Velocity Log (DVL) measurements, which degrade the navigation accuracy of the Strapdown Inertial Navigation System (SINS)/DVL integrated system, this paper proposes a soft-gating Gaussian–Student’s t mixture robust Kalman filter (MRKF). Firstly, the measurement noise is modeled as a mixture of Gaussian and Student’s t distributions to adapt to normal stationary noise and abrupt outliers, respectively. Secondly, a logistic soft-gating weight is constructed based on the innovation Mahalanobis distance to adaptively balance the output contributions of the standard Kalman Filter (KF) and the variational Bayesian Student’s t filter. Finally, moment matching is adopted to realize the weighted fusion of two-branch posterior distributions, and an equivalent Gaussian posterior estimation is obtained. Simulation results under the considered SINS/DVL integrated navigation scenarios show that the proposed MRKF maintains estimation accuracy close to the standard KF under nominal Gaussian measurement noise. In the designed DVL outlier-injection scenario, the proposed MRKF achieves a position RMSE of $53.39\mathrm{m}$, compared with $878.75\mathrm{m}$, $58.84\mathrm{m}$, and $56.49\mathrm{m}$ for the nominal KF, Huber KF (HKF), and Student’s-t variational Bayesian KF (STVBKF), respectively. These results indicate that the proposed MRKF can improve robustness against DVL outliers while maintaining competitive estimation accuracy under the simulated conditions. Full article

Background/Objectives: Hypertrophic cardiomyopathy (HCM) in childhood is associated with a risk of adverse cardiovascular events despite preserved left ventricular (LV) ejection fraction (EF). The aim of this study was to evaluate echocardiographic parameters of longitudinal LV systolic function and determine their relationship with cardiac magnetic resonance (CMR) findings and major adverse cardiovascular events (MACE) in children and adolescents with HCM. Methods: This single-centre prospective observational study enrolled 31 children and adolescents with HCM and preserved LV EF. Echocardiographic assessment included mitral annular plane systolic excursion (MAPSE), tissue Doppler mitral annulus systolic velocity (s′), mitral annular displacement index (MADI), and LV global longitudinal strain (GLS). Investigated CMR parameters encompassed LV mass, maximal wall thickness, and late gadolinium enhancement (LGE). Associations between echocardiographic and CMR findings were analyzed, and the discriminative value of longitudinal function parameters for MACE was assessed. Results: Impaired longitudinal systolic function was frequently detected in our cohort. Lower MAPSE and s′ z-scores were present in 61.3% of patients, reduced MADI in 96.8%, and reduced LV GLS in all subjects. Patients with MACE showed significantly lower MADI (p < 0.001) and worse LV GLS (p = 0.003). An exploratory LV GLS cut-off value of −12.1% showed discrimination for MACE in this cohort, with 75% sensitivity and 95.7% specificity. Echocardiographic parameters significantly correlated with CMR markers of hypertrophy and fibrosis, particularly LV GLS, which demonstrated the strongest associations with LV mass and the presence and extent of LGE. Conclusions: Echocardiographic parameters of longitudinal LV systolic function could contribute to closer clinical surveillance in children and adolescents with HCM. LV GLS may identify subtle myocardial dysfunction and provide exploratory prognostic information; however, its role in risk stratification requires prospective validation in larger pediatric HCM cohorts. Full article

Magnetostrictive patch transducers (MPTs) are highly efficient for generating and detecting ultrasonic waves for non-destructive evaluation (NDE), though their use on cementitious media and fibre-reinforced concrete has not yet been investigated. In this study, a COMSOL simulation, validated with laser-Doppler vibrometry, was first used to quantify patch deformation for use in subsequent simulation of wave propagation in samples. The MPT system was then validated on thin glass plates, producing tunable A₀, S₀, and SH₀ modes through frequency-wavelength matching. In cementitious mortar plates, SH₀ and SH₁ modes were demonstrated experimentally for the first time using MPTs. The validated COMSOL model was then used to interpret complex signals in quasi-plate and half-space cementitious mortar prisms, showing that MPTs generate Rayleigh, bulk SH, and surface-skimming SH modes. In steel fibre-reinforced concrete, surface-skimming SH wave speed correlated with increases in breaking strength even in the presence of surface features such as notches. Notably, Rayleigh wave speeds could not be measured in the presence of surface features, and the Rayleigh velocities measured in the same sample, but not in the local tested area did not correlate with SH speed. This behaviour is likely due to the non-uniform distribution of material constituents, including fibre-reinforcement and coarse aggregate, combined with the different propagation paths and depth sensitivities of the reported wave modes. Overall, racetrack-coil MPTs enable multimodal inspection of cementitious media, providing information on the presence of geometric features and material properties. Full article

Local impedance variations in structural waveguides partially reflect and absorb incident
flexural waves, motivating wave-based strategies for passive vibration control. This study
develops and experimentally validates a wave-energy framework to quantify and optimize
flexural wave absorption by Kelvin–Voigt attachments on a finite Timoshenko beam.
A finite element model is validated against Scanning Laser Doppler Vibrometry measurements
from a clamped–clamped aluminum beam with a passive damper mounted near
one end, with dashpot parameters identified through two independent approaches and
the discrepancies attributed to parameter uncertainty. Wave decomposition of the simulated
and measured velocity fields yields the power reflection coefficient ρ(ω) and power
absorption coefficient α(ω) over the 0–15.3 kHz band. The spring stiffness and damping
coefficient exhibit frequency-dependent optima and act as complementary, jointly tuned design
variables. Expressing dashpot location in wavelength-normalized coordinates reveals
a recurring spatial pattern in which absorption minima cluster around half-wavelength
multiples, while multiple spanwise positions yield near-peak absorption at any given
frequency. This pattern is governed primarily by the flexural wavelength, decoupling
placement from parameter tuning, and persists across clamped–clamped, clamped–free,
and free–free boundary conditions. Two independently tuned dampers further broaden the
effective absorption band by suppressing local minima in α(ω). These results demonstrate
that measurement-driven wave decomposition provides compact, physically grounded
guidelines for passive damper placement in beam structures. Full article

Background/Objectives: Although vascular mechanisms are increasingly implicated in the etiology of sudden sensorineural hearing loss (SSNHL), the inability to directly visualize the labyrinthine artery remains a diagnostic obstacle. Sharing embryological and physiological parallels with the inner ear, the eye represents an accessible surrogate organ capable of reflecting systemic microvascular status. This study aimed to evaluate the diagnostic value of ocular hemodynamic and structural parameters in patients with acute unilateral idiopathic SSNHL. Methods: This prospective, comparative, cross-sectional study enrolled 30 patients with acute unilateral idiopathic SSNHL and 25 age and sex matched healthy controls. Three groups were defined: the affected eye, the contralateral eye, and the control eye. Retrobulbar hemodynamics (PSV, EDV, RI, PI) were assessed by color Doppler imaging; peripapillary choroidal thickness, RNFL, GCC+, and macular thickness by swept-source OCT; and macular microvascular perfusion by OCT angiography. Results: End diastolic velocity in the posterior ciliary arteries was significantly reduced in both patient eye groups relative to controls (p < 0.001), while RI and PI were significantly elevated (p = 0.001 and p = 0.004, respectively). Comparable hemodynamic impairment was observed in the ophthalmic artery. Peripapillary choroidal thickness was bilaterally reduced in the inferior and temporal quadrants in both patient groups (p = 0.003 and p = 0.010). No significant difference was detected between affected and contralateral eyes in any parameter. RNFL, GC+, and macular thickness remained comparable across all groups. Conclusions: The bilateral symmetry of hemodynamic impairment and choroidal thinning suggests that SSNHL arises against a background of systemic microvascular disease. The combined use of OCT and color Doppler ultrasonography holds clinical potential as a non-invasive biomarker panel for defining the vascular phenotype of the condition. Full article

On background cosmological scales, after subtraction of peculiar velocities and local bound-system motions, observed cosmological signals are redshifted rather than blueshifted. Yet, redshift alone does not distinguish the past lightcone of an expanding Universe from the future lightcone of a contracting one. In practice, the identification of the observed redshifted branch with the observational past is set primarily by electromagnetic radiation, whose retarded character is independently established in controlled physics, albeit over non-cosmological scales. From that perspective, the observed cosmological arrow is not separable from the causal/radiative prescription used to interpret the signals. This effective entanglement between the cosmological and the radiative arrows should nevertheless be distinguished from the notion of arrow used in the present work. Here instead, the relevant arrow is not thermodynamic but kinematic; it is defined by the symmetry or asymmetry of background lightcone observables under $\xi \leftrightarrow -\xi$, where $\xi \equiv ln(1+z)$ and z is the redshift—a criterion motivated directly by the time-reversal-symmetric special-relativistic longitudinal Doppler shift. Equivalently, the arrow considered here is the observed redshift/blueshift asymmetry of cosmological lightcone signals; retarded observations of an expanding FRW Universe are in the redshifted branch, whereas the opposite rapidity orientation would correspond to the blueshifted branch. This naturally suggests using rapidity-reversal symmetry as the redshift-space no-arrow condition when passing from special relativity (SR) to Friedmann–Robertson–Walker (FRW) cosmology, where the empty Milne Universe is a bridging borderline case. In fact, the viewpoint advocated here is that $\xi$-symmetry/asymmetry is practically more fundamental than t-symmetry/asymmetry simply because the former is more readily related to cosmological observables. It is shown here that generic non-empty FRW Universes possess an intrinsic $\xi$-asymmetry already at the background level, independently of entropy, coarse-graining, structure growth, or a Past Hypothesis. Full article

Background/Objectives: Rheumatoid arthritis (RA) has been associated with accelerated atherosclerosis and cerebrovascular alterations. Our 2017 study compared 60 RA patients to healthy controls, assessing vascular, neurological, and cognitive parameters. The present study is a follow-up of these RA patients to evaluate disease progression and vascular changes over time, using their 2017 results as baseline. Methods: In 2023, we reassessed 43 of the original 60 RA patients using laboratory testing, carotid ultrasound, functional transcranial Doppler (TCD) and brain magnetic resonance imaging (MRI) examinations. Changes over time were analyzed within the same individuals. Results: Inflammatory markers and lipid profiles showed a trend toward improvement, though changes were not statistically significant, except for a significant increase in vitamin D (p < 0.001) and a decrease in Disease Activity Score in 28 Joints (DAS28) scores (p < 0.001). Carotid ultrasound revealed a significant increase in plaque burden (p = 0.022 on the right side and p = 0.008 on the left), while carotid intima media thickness (cIMT) showed a non-significant rise. TCD measurements indicated significantly increased pulsatility (p < 0.001 on the right, p = 0.001 on the left side) and resistance (p = 0.001 on the right, p = 0.012 on the left side) indices and reduced flow velocities (p < 0.001 on the right and p = 0.001 on the left side) in bilateral middle cerebral arteries (MCAs). The cerebrovascular reserve capacity was significantly lower on the right side overall (p = 0.013), with further decline noted in the methotrexate (MTX)-treated subgroup on the left side (p = 0.043). MRI findings showed non-significant numerical trends toward worsening lacunar small-vessel disease (p = 0.405) and cerebral atrophy (p = 0.063), with higher but stable lacunar infarction scores among MTX users (p = 0.023). Conclusions: Despite improved inflammatory control, RA patients demonstrated progressive vascular and hemodynamic alterations over time, while MRI changes should be interpreted as trends. These findings support multimodal vascular monitoring in RA. Full article

Understanding the dynamics of the urban atmospheric boundary layer is critical for accurate meteorological and air quality modeling. Utilizing one year of continuous Doppler wind lidar observations, this study investigates the seasonal and diurnal variability of wind fields, low-level jets (LLJs), and mixing-layer height (MLH) at an urban site in Beijing. Results show that horizontal winds are strongest in winter and spring and weaker in summer, with northwesterly flow dominating in winter and more diverse patterns in summer, while the corrected vertical-velocity distributions show seasonally varying structures and are interpreted cautiously as frequency-distribution characteristics. A distinct diurnal phase reversal in wind speed is identified near 0.3 km. LLJs occur predominantly at night, with core heights descending from 1.2–1.6 km in winter to 0.6–0.8 km in summer, and are associated with enhanced vertical shear. MLH reaches its deepest development in spring, with clear-sky peaks exceeding 1.5 km, while summer growth is comparatively limited and is associated with stronger latent heat partitioning. These findings indicate that wind fields, LLJs, and MLH exhibit coherent seasonal and diurnal covariations, while their direct causal relationships require further process-oriented analysis. This study provides a year-long observational basis for evaluating urban ABL parameterizations. Full article

Distributed passive acoustic tracking is an important technique for detecting and localizing a non-cooperative underwater target, in which the frequency difference of arrival (FDOA) is a widely used measurement. FDOA reflects the differences in the target’s radial velocity relative to spatially distributed receiving nodes through Doppler-induced variations in the instantaneous frequencies of line-spectrum components. However, conventional FDOA-based methods rely heavily on the stable and accurate estimation of instantaneous line-spectrum frequencies, and their performance degrades when the line spectrum is affected by frequency fluctuations caused by target operating variations and external disturbances. To address this issue, this paper proposes a new measurement, the cross-correlation frequency difference of arrival (CFDOA), which exploits the temporal correlation of line-spectrum to characterize inter-node radial-velocity differences and reduces the reliance on accurate instantaneous-frequency estimation. To evaluate the effect of the proposed CFDOA measurement on positioning performance, a unified FDOA/CFDOA measurement equation is established within the same target position estimation framework. In addition, for scenarios with a limited number of receiving nodes, a recursive estimation scheme combining constrained initial-state search and particle filtering is developed. The simulation and sea-trial results demonstrate that, in the presence of line-spectrum frequency fluctuations, the proposed CFDOA measurement yields more accurate position estimates than conventional FDOA. Full article

In the context of aircraft engine technologies, sprays are used to inject water into the engine cycle to enhance efficiency and reduce emissions. Accurate specification of droplet injection boundary conditions is therefore essential for reliable numerical predictions. This study presents a numerical validation of a water spray configuration previously characterized using phase Doppler anemometry. An Euler/Lagrange approach is applied to simulate the spray using two distinct injection strategies: an array of injector points (Case 1) and a solid-cone injector (Case 2). Numerical results are compared with experimental data to assess droplet size and velocity distributions. Both approaches capture the main spray characteristics, while Case 1 provides improved agreement due to a more accurate representation of the injection conditions. In addition, the influence of droplet–droplet collisions is investigated using different collision-regime maps. While the collision models lead to significantly different collision outcomes, only minor differences are observed in spray characteristics, with noticeable deviations occurring in the downstream region. Overall, the results demonstrate the importance of accurate injection modeling for reliable spray predictions, while simpler injection approaches remain viable with reduced accuracy. The influence of collision modeling is limited under the present conditions and for the investigated spray metrics, providing insight into its role and limitations in polydisperse sprays. Full article

Utilizing underwater vehicles for hydropower infrastructure inspection is increasingly vital. However, these GNSS-denied and confined environments pose significant navigation challenges: Inertial Navigation Systems (INSs) suffer cumulative drift, Doppler Velocity Logs (DVLs) face acoustic blind zones near walls, and visual navigation frequently fails in highly turbid waters. To address these issues, this paper proposes a tightly coupled multi-source (INS/acoustic/optical/vision) navigation algorithm leveraging prior wall geometry constraints. Developed within an Error-State Kalman Filter (ESKF) framework, the model seamlessly accommodates sensor spatiotemporal heterogeneity. To overcome optical failures, a structural surface constraint model is innovatively constructed using single-beam sonar ranging. The core contribution involves transforming sonar ranging data into 6-DOF spatial pose constraints based on the dam’s planar characteristics, effectively bounding the localization drift perpendicular to the surface. Field experiments at the hydropower station dam demonstrate that under extreme conditions with total visual failure, the proposed algorithm effectively constrains critical motion degrees of freedom. By maintaining the wall-tracking error within 0.08 m (Root Mean Square Error, RMSE)—which effectively represents the relative localization error given the known absolute position of the structural wall—this method significantly enhances the operational robustness and precision of close-wall inspections in extreme underwater environments. Full article

The global transition to a diversified renewable energy portfolio requires reliable assessment of predictable marine energy resources. This study develops a high-resolution, three-dimensional Regional Ocean Modeling System (ROMS) to quantitatively evaluate theoretical tidal current energy resources in the Bohai and Yellow Seas. The model, configured with fine-scale bathymetry and forced by harmonic tidal constituents, is validated against tide gauge and Acoustic Doppler Current Profiler (ADCP) observations. Multi-year simulations reveal pronounced spatial heterogeneity in tidal current energy distribution. Rather than treating resource assessment as a single power density mapping exercise, this study combines annual mean theoretical power density, peak theoretical power density, threshold-dependent effective flow duration, effective water depth, current directionality, and vertical velocity structure to characterize resource intensity, temporal persistence, and vertical deployability. The results identify distinct hydrodynamic resource regimes. High theoretical resource intensity is concentrated west of Laotieshan Cape and east of Chengshantou, where cumulative annual effective flow duration exceeds 5000 h and short-term instantaneous theoretical power density can reach approximately 10 kW/m² and 8 kW/m², respectively. These peak values indicate strong local tidal acceleration but should be interpreted together with annual mean power density and effective flow duration. In contrast, the northern Jiangsu coastal area exhibits lower peak intensity but relatively persistent moderate flow conditions. The results provide a hydrodynamic resource basis for preliminary site screening and for guiding subsequent turbine-performance, wake/array, environmental, grid accessibility, and techno-economic assessments. Full article

(1) Background: Cardiovascular disease represents the leading cause of morbidity and mortality in patients with autosomal dominant polycystic kidney disease (ADPKD), often developing early in the disease course, even in the presence of preserved renal function. We aimed to evaluate circulating heart-type fatty acid–binding protein (H-FABP) as a marker of subclinical cardiac involvement and cardiorenal interaction in ADPKD. (2) Methods: In this single-center observational study, 80 adult patients with ADPKD receiving tolvaptan therapy were evaluated using echocardiography, renal function parameters, and circulating H-FABP levels. Associations between H-FABP and echocardiographic indices of cardiac structure and function, as well as renal parameters, were assessed using linear regression models. In addition, a composite severity score integrating CKD stage and H-FABP levels was constructed to assess the combined cardiorenal burden. (3) Results: Higher H-FABP concentrations were significantly associated with echocardiographic markers suggestive of subclinical cardiac involvement, particularly parameters related to impaired myocardial relaxation, including lower E/A ratio and reduced tissue Doppler e′ velocities. These associations remained significant after adjustment for renal function and relevant clinical covariates. In parallel, H-FABP levels were also associated with markers of renal disease severity, including lower baseline eGFR and greater total kidney volume. The composite severity score showed a graded association with echocardiographic parameters, with a progressive trend toward less favorable diastolic indices as risk categories increased. These findings suggest a potential complementary role for H-FABP in the integrated evaluation of cardiorenal involvement in ADPKD. Given the cross-sectional design and single-centre setting, these results should be considered hypothesis-generating and require prospective validation in larger, independent cohorts. Full article

Autonomous Underwater Vehicles (AUVs) are increasingly used in deep-sea exploration, environmental monitoring, and marine engineering. Their operational safety and mission performance rely heavily on accurate and long-endurance underwater localization. However, both single-sensor localization methods and existing multi-sensor fusion approaches have inherent limitations, making it difficult to achieve high-precision localization during long-duration missions. To address this issue, this study develops a deep-learning-based multi-source sensor fusion framework for AUV localization. In the proposed framework, high-frequency data from the Inertial navigation system (INS) and Doppler velocity log (DVL) are used for continuous position propagation, while low-frequency absolute position observations from the Ultra-short baseline (USBL) system and Sonar are used to periodically correct the propagated results. Based on this framework, three instantiated models are developed using a Deep neural network (DNN), a Long short-term memory (LSTM) network, and a Bayesian semi-supervised mixed shallow-layer neural network (BSsMSLNN), respectively. Comparative experiments are conducted against the Extended Kalman filter (EKF) and Simultaneous localization and mapping system using Sonar, Visual, Inertial, and Depth sensor (SVIn2). The results show that the proposed framework effectively suppresses long-term error accumulation and significantly improves localization accuracy. Among the evaluated models, the BSsMSLNN-based method achieves the best performance in terms of trajectory fitting, root mean square error (RMSE), and coefficient of determination (R²). The proposed method provides a feasible solution for high-precision autonomous navigation of AUVs in GPS-denied environments. Full article

Classification of ground and low-altitude targets in radar remote sensing is challenging because environmental clutter and noise can significantly degrade the discriminability of target echoes, especially under complex outdoor observation conditions. To improve the classification performance for humans, vehicles, and unmanned aerial vehicles (UAVs), this paper proposes a velocity-aware multi-feature fusion method based on measured radar echo data. First, radar echoes are preprocessed using a wavelet-decomposition-based strategy to suppress clutter and noise while preserving useful target information. Then, multiple complementary features, including wavelet packet energy distribution, spectral entropy, spectral standard deviation, temporal standard deviation, amplitude dispersion coefficient, and relative radar cross-section (RCS), are extracted to characterize the target echoes from different perspectives. Considering the influence of target velocity on Doppler distribution and class separability, the measured data are further divided into different velocity intervals for stratified classification. Based on the fused feature vectors, a long short-term memory (LSTM) network is employed to model feature relationships and perform target classification. Experiments conducted on real measured radar echo data demonstrate that the proposed method achieves classification accuracies of 97.82% for UAVs, 96.00% for vehicles, and a mean interval-level accuracy of 96.94%, indicating its effectiveness for ground and low-altitude target classification in cluttered radar remote sensing environments. Full article