Search Results (531)

MEMS resonators vibrate about equilibria deflected by whatever combination of temperature, pressure, and bias voltage is present—not about the flat, unloaded plate—raising a basic design question: does the resulting natural frequency depend on the specific loads that produced the deflection, or mainly on the deflection itself? We address this for annular and circular plates through a self-contained derivation of the governing multi-load equations and the linearized vibration eigenvalue problem about an arbitrary thermal, mechanical, and electrostatic equilibrium, validated against two classical benchmarks and applied to a parametric study spanning radius ratio, Poisson’s ratio, and five load combinations at matched deflection. The spread in squared frequency, ${\omega }_1^2$, across combinations shrinks monotonically from $29\%$ at $w/h=0.4$ to $6\%$ at $w/h=2.4$, a dynamic counterpart to a known static result in which the large-deflection boundary layer at a clamped edge depends only on the local membrane stress, not on which loads produced it. Going beyond the linear eigenfrequency, a single-mode Duffing-type reduction, compared against four independent classical benchmarks, reproduces the same asymmetry direction and hardening-to-softening crossover reported in the literature. For the one annular geometry and axisymmetric motion studied here, the results suggest that once deflection exceeds about twice the plate thickness, resonator frequency can be tabulated against deflection amplitude alone, rather than the full space of operating conditions. Full article

This paper presents a combined CFD and experimental investigation of water flow through a Shootfire-1000 water-foam fire monitor. The study aimed to assess pressure losses, flow characteristics, hydraulic stability, and cavitation risk, and to evaluate the influence of selected geometric and operating parameters on hydraulic performance. A numerical model based on the actual geometry of the device was developed and experimentally validated using pressure loss measurements obtained under representative operating conditions. The influence of flow rate, monitor elevation angle, water temperature, nozzle cone position, and cone plate fillet radius was analyzed. The results showed that the dominant pressure losses occur within the monitor head, particularly in the annular constriction formed by the nozzle cone and the housing. Water temperature and monitor elevation angle had only a minor effect on the overall hydraulic performance, whereas relatively small modifications of the nozzle cone geometry significantly affected pressure losses. The analyses further demonstrated that local geometric features play a key role in determining velocity distribution and hydraulic stability. No pressure values below the water vapour pressure were observed within the investigated operating range, indicating a negligible risk of cavitation. The results confirm that optimization of the monitor head geometry can effectively reduce hydraulic losses and improve the hydraulic performance of water-foam fire monitors. Full article

Background: Congenital colonic stenosis (CCS) is a rare cause of neonatal bowel obstruction due to a focal luminal narrowing. We report a premature infant in whom a high-grade CCS remained clinically compensated for months during exclusively liquid feeding. Case Presentation: An 8-month-old corrected-age female infant (born at 28⁺⁵ weeks’ gestation; body weight (BW): 1095 g) presented to the Emergency Department with acute abdominal distension, bilious emesis, and obstipation, despite a history of steady weight gain and chronic mild abdominal distension. A neonatal contrast enema had previously shown an abrupt cutoff suggestive of obstruction, but this was attributed to a procedural artifact given her tolerance of feeds and passage of loose stools; a rectal suction biopsy excluded Hirschsprung disease. Within four days of introducing complementary solid foods at 8 months corrected age, her compensation failed and complete functional obstruction developed. A repeat contrast enema confirmed a short-segment, annular stenosis of the distal descending colon. Conservative management with a liquid diet failed, and definitive surgical resection with primary anastomosis was performed approximately one month later, achieving immediate symptom resolution and long-term catch-up growth. Conclusions: Reassuring weight gain and liquid stool passage can create a diagnostic trap, masking a high-grade colonic structural obstruction. Clinicians must not disregard reproducible focal anomalies on neonatal contrast imaging based solely on clinical plausibility. Full article

Eccentric reaming tools are widely integrated into bottom-hole assemblies during while-drilling reaming operations to improve borehole quality and enhance drilling-assembly passability. However, their eccentric geometry introduces periodic tool–borehole contact, friction, and impact excitations, which may adversely affect the dynamic stability of the drilling system. In this study, a process-oriented finite element dynamic model of a bottom-hole assembly incorporating a bidirectional eccentric reaming tool was developed to investigate coupled radial, axial, and torsional vibration responses under different stabilizer configurations. Three configurations, namely the near-bit, single-stabilizer, and double-stabilizer configurations, were systematically compared. The results indicate that the double-stabilizer configuration produces the most continuous and regular annular borehole profile and promotes a more stable tool–borehole contact state. Compared with the other configurations, it provides stronger lateral constraint, yields the lowest radial-displacement fluctuations, reduces radial and axial acceleration responses, and mitigates longitudinal impacts. The near-bit configuration exhibits the most pronounced torsional instability, including transient reverse rotation of the reaming tool, whereas no reverse rotation occurs under the double-stabilizer configuration. An orthogonal design was further conducted to optimize the operating parameters. Range analysis shows that rotational speed has a greater influence on the radial-displacement root-mean-square value than weight on bit within the investigated parameter range. The optimal operating condition was identified as a rotational speed of 50 rpm and a weight on bit of 80 kN. These findings demonstrate that bilateral stabilizer support can improve borehole regularity, suppress coupled vibration, and enhance the operational stability of while-drilling eccentric reaming systems. Full article

Trapped annular pressure is among the primary well integrity risks for deepwater wells, particularly under high-temperature and high-production-rate conditions. The application of thermally insulated fluid to mitigate trapped annular pressure offers the advantages of low cost and convenient operation, yet its applicability still requires systematic evaluation. To investigate the mitigation effect, this paper establishes a model by coupling radial heat transfer between the wellbore and surrounding formations based on annular volume compatibility. The model is mainly composed of two modules: temperature calculation and pressure calculation. A segmented iterative algorithm is adopted to solve the model, which enables quantitative analysis of the variation law under different conditions. Via the proposed model, this paper analyzes the influences of thermal conductivity, production rate, production time and geothermal gradient on trapped annular pressure. The results indicate that thermally insulated fluid can effectively reduce trapped annular pressure, and the mitigation effect becomes more significant as thermal conductivity decreases. Among different injection schemes, the optimal control performance is achieved when thermally insulated fluid is injected into the A annulus. Compared with conventional annular fluids, the B-annular pressure decreases from 50.71 MPa to 21.52 MPa when the thermal conductivity of thermally insulated fluid is reduced to 0.1 W/(m·°C). Thermally insulated fluid still maintains effectiveness under high-temperature and high-production-rate conditions, and its thermal conductivity should preferably be controlled below 0.15 W/(m·°C). Combined thermal insulation measures are recommended for long-term production under high production rate and high temperature. The maximum allowable annular pressure should be determined based on the strength of the C annulus, so as to provide a design criterion for the thermal insulation design. Full article

Inefficient xanthate transport and poorly defined circulation paths can limit the conditioning of low-grade lead–zinc tailings. A Venturi-assisted composite conditioning tank was therefore evaluated using ANSYS Fluent 2025 R2 (Ansys Inc., Canonsburg, PA, USA). The volume of fluid (VOF) model described the air–slurry free surface, the renormalization group (RNG) k–ε model and multiple reference frame (MRF) approach represented the impeller-induced mean flow, and a transient user-defined scalar (UDS) described the transport of a generic normalized xanthate tracer. The slurry phase was represented as a generic homogeneous equivalent medium rather than as a fully characterized solid–liquid suspension. The Venturi throat generated a local low-pressure region and stable reagent suction; at a tailings inlet velocity of 2.50 m·s⁻¹, the reagent-branch inlet mass flow rate was 2.825 × 10⁻⁴ kg·s⁻¹. Parameter comparisons identified 350 r·min⁻¹, an impeller installation height of 370 mm, and an annular gap width of 60 mm as the preferred combination. The calculated impeller power increased from 0.211 kW at 200 r·min⁻¹ to 2.304 kW at 400 r·min⁻¹. Increasing the speed from 350 to 400 r·min⁻¹ raised power consumption by 60.9% but average velocity by only 5.8%. Compared with a conventional tank, the composite tank formed a coherent impeller–lower connecting–annular upflow–upper recirculation pathway, providing more favorable hydrodynamic conditions for xanthate transport and potential reagent–particle contact. Full article

This paper presents the design, numerical analysis, and experimental investigation of a compact traveling-wave piezoelectric motor for continuous and incremental angular motion. The key advancement of the proposed design is a compact coaxial direct-drive architecture that combines a single ring-shaped piezoelectric stator with four independently excited electrode sections, three discrete spherical contact elements, a cone-shaped rotor, and an adjustable spring-based preload mechanism. In contrast to conventional traveling-wave motors employing continuous annular or toothed contact interfaces, the proposed configuration localizes the stator–rotor interaction at three predefined contact points while allowing both continuous bidirectional rotation and incremental angular positioning within the same actuator. Numerical analysis identified the operating mode at 39.95 kHz and confirmed the formation of elliptical displacement trajectories at the spherical contact elements. The calculated resonance frequency and effective electromechanical coupling coefficient were 39.93 kHz and 4.36%, respectively. Experimental measurements showed resonance of 39.94 kHz with an effective coupling coefficient of 4.47%. The motor achieved a maximum rotational speed of 87 ± 2.2 RPM at 180 V_p-p. The maximum stall torque reached approximately 8.3 N·mm and 8.4 N·mm for clockwise (CW) and counterclockwise (CCW), respectively, at 180 V_p-p. Depending on the excitation amplitude, the angular step varied from 0.082 ± 0.015° to 3.038 ± 0.120°. The results confirm that the proposed compact motor can provide controllable continuous rotation and incremental angular positioning. Full article

A unified modeling framework is presented in this work to predict the free vibration and loss factor characteristics of damping sandwich rotational plates. The formulation starts from the first-order shear deformation theory, where the zigzag hypothesis and interlayer displacement continuity are combined to couple the displacement fields of the individual plies. An artificial spring scheme is adopted to enforce the layer–layer compatibility and the external boundary restraints, which leads to a Lagrangian functional composed of the kinetic energy, the strain energy, and the potential energies contributed by the boundary and coupling springs. The displacement unknowns are discretized with Chebyshev polynomials of the first kind, and the natural frequencies and damping loss factors are extracted by solving the resulting eigenvalue problem with the Rayleigh–Ritz method. Convergence tests are conducted, and the reliability of the model is validated against finite element results. Finally, a series of numerical examples is presented to systematically investigate the effects of key model parameters on the vibration characteristics of the structure. The results indicate that increasing the thicknesses of the inner and outer layers of the damping sandwich rotational plate structure can significantly raise the natural frequencies. Increasing the inner diameter helps to reduce the area of the low-frequency region, where the difference between the two sides exceeds 40 Hz, caused by the close thicknesses of the inner and outer layers. When only the outer boundary is clamped, the natural frequencies of the annular plate are more than twice those of the solid rotational plate, although the solid rotational plate yields a larger loss factor. When only the outer circular edge is fixed, increasing the total thickness of the structure can effectively raise the natural frequencies, with a maximum increase exceeding 110 Hz, while the loss factor decreases significantly. Full article

Non-uniform discharge temperature during sinter cooling is a practical issue in ironmaking, as local overheating may increase the thermal load on downstream conveying equipment. To mitigate insufficient cooling in the upper sinter bed under the conventional bottom-blowing mode, this study developed a three-dimensional transient CFD model for an industrial continuous annular cooler and optimized the air-supply strategy in Zones IV and V. Under the conventional condition, ambient air is supplied independently to Zones IV and V from the bottom wind boxes. In the novel air-supply strategy, while keeping the total fresh cooling-air flow rate in the final cooling region unchanged, ambient air is introduced from the upper side of Zone V and discharged from its bottom; the outlet gas from Zone V is then supplied to the bottom of Zone IV, forming a serial air-supply path. The results show that the novel arrangement improves the spatial matching between the cooling gas and the sinter bed during final cooling and suppresses the local high-temperature region near the discharge end. The maximum discharge temperature decreases from 459 K to 410 K, below the process limit of 423 K, while the average discharge temperature decreases from 377 K to 364 K. Based on the enthalpy-flow difference calculation, the predicted recoverable waste heat also increases under the novel condition. These findings suggest that redesigning the gas-flow route in the final cooling region can effectively enhance the uniformity of the discharge temperature in industrial annular coolers. Full article

The formation pressure system of ultra-deep wells is complex, and managed pressure cementing (MPC) is a commonly used technical means of safety control and cementing quality improvement. During the MPC process, pump switching operations can induce substantial annular back-pressure. The attenuation of annular back-pressure within the wellbore serves as a pivotal foundation for the precise determination of back-pressure compensation values in ultra-deep wells. Building upon the one-dimensional transient flow model of the wellbore, we developed a transient transmission model for annular back-pressure and solved it using the finite difference method. The computational results were validated against experimental data, thereby elucidating the attenuation pattern of annular pressure waves in ultra-deep wells. The findings reveal that the primary controlling factors for the attenuation of pressure waves encompass well depth, the elastic modulus of the wellbore rock, and the rheological model of the drilling fluid. As well depth increases, the pressure wave exhibits a linear decrease, with discontinuities occurring at the casing and open-hole sections. The rate of pressure wave attenuation accelerates within the open-hole interval. The lower the elastic modulus of the open-hole segment, the more rapid the attenuation rate of the pressure wave becomes. The attenuation laws of annular fluids with different rheological models are ranked as follows: Power-law model > Herschel–Bulkley model > Bingham model. Under the computed well conditions, the pressure of the power-law fluid decreases to 85% of its initial back-pressure value. This research provides theoretical underpinnings for the design and execution of on-site MPC operations. Full article

Rainfall-induced landslides result from interactions between terrain predisposition and hydrometeorological forcing. In event-scale susceptibility modelling, uncertainty often arises from non-landslide controls. Locations without recorded failures may differ in rainfall history, storm exposure, or inventory completeness, which can bias models trained on static absence samples. This study develops a hydrometeorological control sampling strategy for rainfall induced landslide susceptibility modelling. The strategy defines each sample by grid cell and rainfall date, and constructs non landslide controls from storm related risk sets. A background predisposition prior is used to screen candidate controls. Regional same date controls, annular hard controls near failed slopes, and cross year rainy season background controls are then integrated to represent complementary hydrometeorological and terrain conditions. Design weights and density ratio calibration are applied to account for control reliability and reduce distribution mismatch between the training sample and the mapping domain. In the sample-level evaluation, the method was evaluated in Pubei County, Guangxi, China, using terrain, geology, land cover, daily and antecedent rainfall, and surface wetness. It outperformed Buffer, LowSlope, and IV Low across five classifiers. Relative to IV Low, mean AUC increased from 0.887 to 0.958, accuracy from 81.8% to 91.6%, and Kappa from 63.6% to 83.3%. Holdout validation of two July 2006 landslide clusters also showed greater concentration in top-ranked areas. Averaged over RF and GBDT, top 10% capture rose from 0.227 to 0.322, while the frequency ratio increased from 2.264 to 3.213. These findings suggest that, under the evaluated conditions, the strategy improves sample discrimination, increases landslide concentration in areas ranked as highly susceptible, and reduces uncertainty in the selection of nonlandslide controls. Full article

Air-void distribution is an important internal characteristic of asphalt mixtures, as it affects compaction quality, moisture susceptibility, permeability, and long-term pavement durability. Conventional air-void testing methods generally provide only an average volumetric parameter and cannot effectively describe the spatial distribution of air voids within cylindrical specimens. To address this limitation, this study proposes a capacitance-based method for characterizing the vertical and radial air-void distribution of asphalt mixtures using a saturated reference field. An annular capacitive sensor was designed for cylindrical asphalt mixture specimens, and its structural dimensions were optimized using capacitance sensitivity and sensitivity-field distribution uniformity as evaluation indicators. Asphalt mixture specimens with different gradations and compaction conditions were prepared and tested under a saturated reference-field measurement scheme. Dielectric indicators derived from capacitance measurements were used to characterize the variation in air-void distribution along the specimen height and across radial regions. Layer-wise air-void measurements were further conducted to validate the vertical distribution results, while radial partition-based indicators were introduced to quantitatively describe the air-void distribution characteristics from the center to the edge of the specimen. In addition, rotation-angle and saturated-condition stability tests were performed to evaluate the robustness of the proposed method. The results indicate that the saturated reference-field capacitance method can effectively reflect the spatial variation in air voids in asphalt mixtures and provides a low-cost, rapid, and non-destructive approach for evaluating air-void distribution characteristics in laboratory-compacted specimens. Full article

Circular shafts are widely used in shield launching and receiving, metro ventilation, municipal utilities, and underground energy facilities. In practical shaft construction, embedded depth design directly affects basal heave safety, material consumption, construction cost, and construction duration. However, conventional design methods for basal heave stability are mostly derived from wide pit assumptions, which may lead to conservative designs when they are directly applied to circular shafts. The scientific challenge lies in the fact that the basal heave mechanism of circular shafts is governed not only by excavation unloading and soil strength, but also by spatial confinement and circumferential arching induced by the closed annular retaining system. To address this issue, this study develops a 2D plane-strain equivalent model and a 3D full-scale numerical model using FLAC3D based on an actual circular shaft project. The spatial evolution of basal heave, retaining wall deformation, support internal force, and plastic zone development is systematically investigated. On this basis, spatial confinement and the arching effect are introduced as quantitative correction coefficients within narrow foundation pit theory, and an improved design method for basal heave resistance and critical embedded depth is proposed by combining the foundation bearing capacity failure mode and circular slip failure mode. The results show that circular shafts with width–depth ratios of 0.3–1.0 exhibit typical narrow excavation behavior. Compared with the 2D plane-strain equivalent model, the 3D model produces smaller deformation, lower support internal force, and more localized plastic zones because the closed circular structure can mobilize circumferential compression and spatial load transfer. The proposed method increases the calculated basal heave safety factor by approximately 15–40% and reduces the required embedded depth by approximately 15–30% compared with conventional code-based methods under the investigated conditions. The study provides an improved theoretical and practical approach for basal heave stability assessment and embedded depth optimization of circular shafts, contributing to safer, more economical, and more sustainable shaft construction. Full article

Background and Objectives: Coronary artery disease may be difficult to detect by resting echocardiography when left ventricular ejection fraction is preserved and regional wall motion abnormalities are absent. This study aimed to assess whether resting Tissue Doppler Imaging-derived mitral annular velocities can help identify CAD in patients with suspected angina pectoris. Materials and Methods: We conducted a cross-sectional observational study of 92 patients hospitalized with suspected angina pectoris who underwent elective coronary angiography at the Institute of Cardiovascular Diseases in Timișoara (January 2025–February 2026). Patients with conditions known to affect TDI-derived parameters were excluded, including previous acute coronary syndrome or myocardial revascularization, significant valvular disease, cardiomyopathies, relevant arrhythmias or conduction abnormalities, permanent pacing, reduced ejection fraction, and pericardial disease. Laboratory and echocardiographic data were collected. ROC curve analysis, univariable logistic regression and multivariable logistic regression were performed to evaluate the diagnostic performance of TDI-derived parameters and their independent association with coronary artery disease. Results: Patients with CAD had significantly lower average E′ values (7.4 ± 1.9 vs. 8.9 ± 1.8 cm/s, p < 0.001) and average S′ values [7.0 (IQR 6.0–7.5) vs. 9.0 (IQR 8.1–10.0) cm/s, p < 0.001], together with higher E/E′ ratios [9.33 (IQR 8.23–11.15) vs. 7.87 (IQR 5.93–9.51), p = 0.002]. Average S′ showed the highest discriminative ability for coronary artery disease, with an AUC of 0.899 (95% CI: 0.819–0.952, p < 0.0001). The optimal Youden-derived cut-off was ≤7.5 cm/s, yielding 77.42% sensitivity and 93.33% specificity. After adjustment for age, male sex, body mass index, diabetes, smoking status, hypertension and LVEF, dichotomized S′ remained an independent predictor of coronary artery disease (OR = 45.49, 95% CI: 8.03–257.68, p < 0.0001), with an adjusted model AUC of 0.92 and 88.04% correct classification. Conclusions: TDI, particularly S′ velocity, may be a useful resting echocardiographic parameter for identifying CAD in selected patients with preserved LVEF and no resting regional wall motion abnormalities. Rather than serving as a universal diagnostic marker, S′ should be considered a complementary, easily obtainable parameter that may improve non-invasive assessment in this specific clinical setting. Full article

Ferrite is an essential functional material for high-power nonreciprocal microwave components, such as circulators and isolators, and its secondary electron emission (SEE) property is critical for suppressing the multipactor effect under vacuum conditions. In this work, we propose a surface engineering strategy based on periodic raised microstructures to regulate the secondary electron yield (SEY) of ferrite coatings/substrates. A Monte Carlo-based numerical method is developed to calculate the SEY of ferrite with hexagonal and annular microprotrusions of varying heights and geometric parameters. The dependence of SEY on microstructure dimensions is systematically analyzed. Spinel ferrite samples with designed microstructures are fabricated via mechanical processing. For hexagonal column arrays with a height of 1.5 mm, a side length of 0.5 mm, and a pitch of 1.67 mm, the maximum SEY is reduced from 2.4 (smooth surface) to 1.7 while the annular concentric protrusion arrays decrease the maximum SEY to 2.1. Effective suppression is achieved over the entire incident energy range for both microstructural designs. Despite a lower reduction, the annular arrays offer geometrically isotropic electron trapping, which may be advantageous for devices with circular or coaxial cavity geometries where directional dependence of the surface texture is undesirable. The results demonstrate that tailored surface microstructures can significantly mitigate SEE of ferrite, providing a promising route for developing high-performance ferrite coatings toward multipactor suppression in space microwave devices. Full article