Search Results (1,246)

Reliable discharge of bulk granular materials is essential for the efficient operation of shaft furnaces, pneumatic conveying systems, and industrial dosing equipment, where uncontrolled arch formation can lead to flow instability and blockage. This study investigates the effect of gas velocity, direction, and configuration on arch formation and collapse during bulk granular material discharge through horizontal orifices. Experiments were conducted using cold quasi-2D (250 × 50 × 5 mm) and hot scale models (cylindrical shaft, D = 300 mm, H = 500 mm) with high-speed imaging (2000 fps, 1280 × 1024) across various materials. Uniform gas flow stabilizes arches, reducing the normalized mass flow rate $W_t/W_0$ to 0.20 ± 0.03 at critical gas velocity ratios $V_1/V_2\le 20$ and area ratios $L_1/L_2\ge 0.37.$ Conversely, localized gas jets increase $W_t/W_0$ to 1.45 ± 0.05. The scientific novelty lies in the development of a unified torque-balance model that, for the first time, predicts critical counter-current gas velocities $V_{kr}$ across different operating configurations with an error not exceeding ±28.9% (n = 3, p < 0.05). Three characteristic discharge regimes—continuous flow, pulsating discharge, and blockage-dominated flow—were identified and related to the stability of dynamically unstable arch structures. These findings provide a quantitative basis for the design and optimization of industrial systems such as shaft furnaces, pneumatic conveyors, and dosing units. Future work will focus on industrial-scale validation, extension to humid or cohesive materials, and investigation of more complex flow geometries to further improve gas-assisted flow control. Full article

Piezoelectric pressure sensors for dynamic monitoring face a trade-off between charge output and measurement range, and existing high-sensitivity designs are largely confined to narrow ranges. This study presents a composite layered piezoelectric pressure sensor in which a 316L stainless-steel diaphragm drives a centrally suspended PZT-5H wafer supported by a perforated alumina gasket, with the wafer thickness and cavity radius optimized under a 10 MPa full-scale stress constraint. Over 0–10 MPa, quasi-static calibration gave a highly repeatable quadratic pressure–charge relationship ($R^2=0.99995$) with a maximum residual below 1% FS. The sensitivity is pressure-dependent: the secant sensitivity increased monotonically from 3.16 pC/kPa at 1 MPa to 5.36 pC/kPa at 10 MPa, reflecting a stress-stiffening response rather than a measurement tolerance band. The output deviation remained within 3% from 25 °C to 150 °C. Shock-tube testing yielded a resonance of ∼50 kHz and a mutually consistent 10–90% leading-edge interval of 10.12 $\mathsf{\mu }$s. Combining high charge sensitivity over a wide 0–10 MPa range with a fast transient response and stable operation up to 150 °C, the proposed sensor is suited to dynamic pressure-pulsation monitoring in fluid-power and thermal and power-plant fluid systems. Full article

Swirling-flow instabilities in hydraulic turbine diffusers constitute a major operational challenge, particularly when Francis turbines operate under part-load conditions. Over the past decades, numerous control strategies have been proposed to mitigate the instabilities associated with swirling flows. This study presents a comprehensive numerical analysis of a passive flow-control technique based on an adjustable diaphragm device, referred to as IRiS. The primary objectives are to attenuate swirling-flow instabilities and to enhance energy recovery within the draft tube. Three-dimensional unsteady flow simulations were performed for multiple IRiS configurations, characterized by different shutter area ratios. The results indicate that the IRiS device can reduce pressure pulsation amplitudes by up to 60% while simultaneously improving pressure recovery. However, the simulations also show that hydraulic losses may increase at part-load operation, depending on the selected IRiS shutter opening. Overall, the findings support the applicability of this passive control concept for both new and rehabilitated Francis turbines operating under off-design conditions, far from the best efficiency point. Full article

Marine pollution monitoring increasingly relies on Biological Early Warning Systems (BEWSs), which use living organisms as continuous, integrative sentinels of water quality. The moon jellyfish Aurelia aurita is a sensitive but under-exploited candidate for this role. We present a computer-vision BEWS pipeline that is unsupervised at inference time and operates without labelled pollution-response data, converting side-view aquarium video of single A. aurita medusae into a binary pollution alarm. Per-frame YOLO bounding-box detections are reduced to a continuous bell-area signal and a centroid trajectory, from which eleven pulsation, kinematic, and detection-quality features are extracted on 60 s sliding windows. A per-animal baseline is fitted on a clean-water baseline (recommended ≥15 min), and a two-layer detector—fast outlier detection on the mean absolute z-score with a k-of-N rule, plus one-sided CUSUM (cumulative sum) accumulation—flags any sustained deviation. Validation on six adult medusae exposed to diesel-WAF detected all six animals (95% CI 54–100%) and produced no false alarms in 203 clean-window opportunities (exact 95% upper bound 1.8%; rule-of-three estimate ≈1.5%). First-alarm latencies ranged from 1.0 to 23.7 min, and the observed responses were described as three descriptive patterns in this pilot dataset: sharp step-change, slow drift, and mixed. The deployed anomaly scoring step contains no neural-network weights, runs in under 300 lines of Python, and is designed for field-portable use in settings where a stationary side-view camera can be positioned alongside an aquarium, although field validation remains required. Per-animal anomaly detection accommodates the strong inter-individual variability of the diesel-WAF response that limits supervised clean-versus-polluted classification at this sample size. Full article

Variable-speed pumped storage units perform flexible and rapid regulation tasks in power grids. However, under the “power-priority” control mode, the superposition of maximum energy operating point and extreme transient events such as load rejection can induce severe vibrations. This study investigates the vibration characteristics of a variable-speed unit under a typical extreme condition (Case RT-5): power-priority mode, maximum energy superposition point, and load rejection at extreme rotational speed. A one-way fluid–structure interaction (FSI) numerical method is employed, combining unsteady Reynolds-averaged Navier–Stokes (URANS) with a shear stress transport (SST) k-ω turbulence model and finite element structural analysis. The innovation lies in quantitatively linking the transient hydraulic excitation (water hammer pressure waves, non-stationary pulsation field) to the mechanical response (centrifugal force, variable stiffness) to identify the root causes of vibration. Results show that under RT-5, the maximum equivalent stress reaches 97.09 MPa and maximum deformation 0.66 mm, occurring at the blade-crown connection root—a stress concentration zone. However, below the material yield strength (265 MPa), the stress rises 2.4-fold within 12 s, and secondary stress peaks appear, indicating high-cycle fatigue risk. Severe fluctuations of stress and displacement, driven by coupled hydraulic-mechanical excitation, are the main causes of vibration. This study provides a theoretical basis for safety assessment and control strategy optimization, and proposes that RT-5 be included as a mandatory verification case for variable-speed units. Full article

Pressure pulsations generated by pumps impair noise behaviour, increase mechanical loading, and reduce control performance in hydraulic systems. This study investigates the use of a rotary mechanical pulsation compensator integrated into the drivetrain of an external gear pump. The aim is to attenuate pulsations directly at their source without modifying the hydraulic layout. This is accomplished by using the torque induced flow rate pulsation to cancel the external flow rate excitation, which leads to destructive interference between flow rate induced and torque induced pressure pulsations. An analytical frequency domain model of the coupled mechanical–hydraulic system is derived to determine the required stiffness and damping conditions. The theoretical results are validated experimentally at mean pressure levels of 100 bar and 170 bar, both for two different hydraulic layouts. With a resonator pipeline at the pump outlet, the first harmonic of the pressure pulsation at the compensation frequency is reduced by 10.9 bar and 18.4 bar, respectively, which corresponds to reduction rates of 93% and 98%. The required damping value depends on the operating conditions, but it is independent of the hydraulic layout. While insufficient damping increases pressure pulsations around the compensation frequency, slightly higher damping flattens the frequency characteristics of pressure pulsation and reduces the maxima around the compensation frequency. In the neighbourhood of this frequency, the proposed concept enables effective reduction of the first pressure pulsation harmonic through a structural modification of the drivetrain. Full article

Background/Objectives: This study aimed to examine the associations between diet-related quality of life (DRQOL) and psychological distress, autonomic dysfunction, and migraine in patients with dizziness and balance disorders. Methods: In this retrospective cross-sectional study, 122 patients (56 men, 66 women; mean age 40.4 ± 12.8 years, minimum 14, maximum 65) from the vertigo outpatient clinic at JR Tokyo General Hospital completed self-reported questionnaires. These included the DRQOL scale, Dizziness Handicap Inventory (DHI), Hospital Anxiety and Depression Scale (HADS), Self-rating Depression Scale (SDS), Orthostatic Dysregulation (OD) checklist, and migraine assessments (POUNDing [Pulsating, duration of 4–72 h, Unilateral, Nausea, Disabling], MIDAS, migraine screener). Correlational analyses, group comparisons, and receiver operating characteristic (ROC) analyses were conducted. Results: Higher DRQOL scores indicate poorer DRQOL. DRQOL scores showed positive correlations with psychological distress (SDS: ρ = 0.57; HADS-A: ρ = 0.50; HADS-D: ρ = 0.53; all p < 0.001) and OD severity (ρ = 0.50, p < 0.001) but not with age, DHI, or individual migraine indices. Migraine screener-positive patients had significantly higher DRQOL scores (p < 0.01). DRQOL alone showed modest ability to discriminate migraine screener-positive from migraine screener-negative patients (AUC = 0.65); discrimination improved to an AUC of 0.77 in a multivariable model that also included age and sex. Conclusions: DRQOL appears to capture psychological and autonomic symptom burden rather than vestibular or headache severity, suggesting that it may serve as a complementary, patient-centered metric that adds a multidimensional perspective to conventional vestibular and headache assessments. Full article

The intensification and continuous evolution of dairy sheep and goat farming have played an essential role in the development and implementation of milking equipment. The increasing demand for time-efficient milking procedures, reduced labour costs, sustained milk production, and optimal mammary health have driven the widespread adoption and optimisation of machine milking technologies. The objectives of this article are (i) the review of milking systems and relevant technological developments in milking equipment and (ii) the evaluation and description of their impact on udder health, as applied on dairy small ruminant farms. Milking systems used on farms depend on the available space and number of animals on the farms. Appropriate settings in milking systems are important for ensuring good milk quality; among them, vacuum level, pulsation rate and ratio are important characteristics that must be monitored regularly. Further, use of appropriate teatcups specific to the animal species to be milked is significant. An important aspect of proper maintenance of the milking system is the cleaning procedure after completion of milking. Points for consideration are quality and temperature of the water used for cleaning, use of detergents and disinfectants, and maintenance schedule and teatcup replacement. Some technological features that are part of milking systems include automatic vacuum shut off, electronic milk recording, electronic identification of animals, automatic flushing of milking clusters and automatic pre-stimulators. Farms will benefit from applying precision technologies, which will use data from tools related to animal genetic background, animal behavioural indicators, environmental conditions and disease-related functions for more holistic and cost-effective farm management. In this context, integration of sensor-based technologies in milking systems will be able to provide real-time information regarding quality of milk produced at individual and farm levels. Moreover, the introduction of automatic system flushing in-between animals during the milking procedure can contribute to breaking chains of potential bacterial transfer and reducing animal infections during milking. Overall, although machine milking has certainly contributed to improved efficiency, milk quality and labour conditions, flaws in system function may adversely affect mammary health. Full article

Pulsator tests are used to characterize the bending fatigue strength of the tooth root. In these tests, the tooth root is loaded not by meshing with another gear but by applying a pulsating load to the tooth flank via a testing machine. This leads to a different S-N curve with respect to the ones obtained through meshing gear tests. This study aims to investigate the impact of cracks in the tooth root on the results of pulsator and meshing tests. Here, we address the issue of load sharing modification during meshing due to the presence of a crack, and its influence on crack propagation. This approach is applied to a real-life example: estimating the finite life of meshing gears based on pulsator tests. This study aims to present an initial procedure for obtaining S-N curves for meshing gears based on those obtained from pulsator tests. The S-N curves obtained from the pulsator test are compensated for by adding the difference in the propagation speed between the two tests calculated by applying the Paris law with parameters extracted from FE simulation; the time spent in propagation is almost doubled in the meshing conditions. Full article

Voltage disturbances occur frequently in power systems. The most important voltage disturbances are voltage unbalance, voltage deviation, and voltage waveform distortions. Voltage waveform distortions are usually considered harmonics, but subharmonics and interharmonics may also occur. Voltage subharmonics are components with frequencies lower than the fundamental frequency. In contrast, voltage interharmonics are components of the frequency spectrum that are higher than the fundamental frequency and are not integer multiples of it. Voltage fluctuations are the superposition of the first voltage harmonic and subharmonic components. This work analysed the shaft torque pulses of an induction motor under single-subharmonic action or under periodic voltage fluctuations combined with voltage unbalance. The experimental results were compared with results from previous work. We also analysed the influence of voltage disturbances on the selection of the coupling connecting the induction motor to the working machine. Full article

In single-phase PWM rectifiers, due to the inherent time-varying characteristics of the source voltage and current as well as the periodic operation of the converter bridge, the instantaneous input power on the AC side inevitably exhibits a twice-fundamental-frequency pulsation. This phenomenon consequently generates a double-line-frequency (100 Hz) voltage ripple on the DC-link capacitor, which causes an inherent contradiction in conventional voltage outer-loop control between steady-state ripple suppression and dynamic response speed. To address this issue, this paper proposes a control strategy based on an Adaptive Time-Delayed Feedforward Neural Network (Adaptive TD-FNN). The proposed method explicitly introduces the delayed voltage error of half a ripple period into the network state input, thereby achieving time-domain decoupling of the 100 Hz low-frequency disturbance. In addition, a physics-driven training framework is constructed by integrating the rectifier’s discrete difference equation, thereby strengthening the network’s capacity to learn the dynamic characteristics of the system. On this basis, a dynamic adaptive smoothness-weight penalty mechanism is designed to adjust the weighting factor of the current command smoothness constraint in the loss function according to the system operating state. Specifically, the penalty weight is increased under steady-state conditions to suppress command oscillations caused by ripple disturbances, while it is rapidly reduced during load or grid-voltage transients to release the network’s transient optimization capability. Simulation and experimental results show that the proposed Adaptive TD-FNN controller can simultaneously achieve smooth steady-state current command output and fast dynamic voltage regulation without introducing additional complex digital notch-filtering algorithms. Compared with conventional dual-loop control, the proposed strategy reduces the total harmonic distortion (THD) of the grid-side input current from 8.45% to 3.42%, satisfying grid-connected power quality requirements. Meanwhile, under large load transients and grid-voltage disturbance conditions, the DC-link voltage recovery time is about 40 ms, verifying the comprehensive advantages of the proposed method in ripple suppression, dynamic response, and operating-condition adaptability. Full article

Pulse oximetry is an essential standard monitor in modern anesthetic practice, enabling continuous noninvasive assessment of arterial oxygen saturation and pulse rate throughout the perioperative period. Since its introduction into clinical medicine, pulse oximetry has significantly improved patient safety by facilitating early detection of hypoxemia and physiologic deterioration. Despite its widespread use, clinicians may underrecognize the technical principles, physiologic assumptions, and limitations that influence measurement accuracy. This review provides a perioperative perspective on pulse oximetry, including the physics of photoplethysmography, sensor technologies, and practical considerations for optimal probe placement and signal acquisition. Sources of inaccuracy such as motion artifact, low perfusion states, dyshemoglobinemias, ambient light interference, skin pigmentation, and venous pulsation are discussed in detail. The review further examines perioperative applications across preoperative evaluation, intraoperative monitoring, and postoperative recovery, while also exploring advanced parameters including perfusion index (PI) and pleth variability index (PVI). Emerging innovations such as multi-wavelength systems and artificial intelligence (AI)-enhanced signal analysis are also highlighted. A comprehensive understanding of pulse oximetry allows anesthesiologists to appropriately interpret monitor data, recognize device limitations, and optimize perioperative patient care. Full article

This study utilizes a large-scale numerical simulation model to investigate the hydrodynamic behavior and particle transport characteristics of gas–liquid–solid three-phase flow in vertical wellbores featuring multi-source confluence and curved geometries. Simulation results indicate that increasing flow velocity shifts the dominant control mechanism from surface tension to inertial forces, transitioning the flow pattern from slug flow to churn flow. In curved pipe sections, centrifugal phase separation and geometric shielding effects cause significant flow asymmetry and maintain large bubble stability at the inner wall. Additionally, the multi-inlet structure induces shear rate gradients that result in the spatial coexistence of two distinct bubble scales. Furthermore, localized gas concentrations exceeding 70% at the upper inlet can trigger severe gas-locking phenomena and intense pressure pulsations. Full article

To address the performance degradation caused by coupling interference between control and identification filters in the active control of ship hydraulic systems, a multi-strategy collaborative optimization algorithm based on “Signal–Amplitude–Time” is proposed. The method constructs a variable-power white-noise module based on power factors to reduce auxiliary noise interference. It employs an improved variable-step-size LMS algorithm to achieve fast and high-precision online identification of the secondary path. Furthermore, an adaptive prediction error filter is introduced to decouple the control and identification processes, effectively resolving the conflict between convergence speed and steady-state precision. Simulation and experimental results demonstrate that the proposed optimization algorithm exhibits superior robustness and adaptive capability under various operating conditions. It can track complex load fluctuations in real time and achieve a line-spectrum pulsation attenuation of more than 90%. This multi-strategy collaborative scheme significantly enhances the pulsation suppression accuracy and dynamic response capability of ship hydraulic systems, providing an efficient and reliable technical approach for the acoustic stealth control of naval ship hydraulic systems. Full article

In spite of the intense research interest in the integration of Pressure Gain Combustion (PGC) systems with a turbomachinery module, limited studies have been conducted regarding the experimental investigation of the strong spatio-temporal perturbations of these unconventional machines’ outflow. This paper focuses on experimentally characterizing the perturbing exhaust flow of a Constant-Volume Combustor (CVC). Preceding numerical analysis offers a transition duct able to attenuate the CVC’s produced unsteadiness and connect this PGC with a turbomachinery module. In fact, the transition duct is manufactured, while a pair of windows are introduced allowing for high-frequency Particle Image Velocimetry (PIV) analysis. In addition, fast-response pressure sensors in the combustion chamber, upstream and downstream of the transition duct, are implemented. A parametric analysis of the rotational frequency of the inlet–outlet rotary valve pair is conducted. The perturbing outflow of this PGC is characterized and experimentally visualized for the first time. Moreover, the attenuation performance of the transition duct on the CVC’s produced unsteadiness is evaluated for different cycle frequencies. The transition duct is proved to be able to alleviate the spatial and time-dependent unsteadiness by CVC, offering crucial evidence and conclusions for the future industrial integration of the CVC with a High-Pressure Turbine stage. Full article