Search Results (1,864)

The effective focal length is a critical determinant of optical performance and imaging quality, serving as a fundamental parameter for components ranging from ophthalmic lenses to precision microlens arrays. With the rapid advancement of complex optical systems in microscopy and smart manufacturing, there is an increasing demand for high-precision measurement techniques that can characterize these parameters with low uncertainty. In this paper, a quadri-wave lateral shearing interferometry (QWLSI) measurement system was developed. A novel precision focal length measurement method of optical lenses based on the principle of QWLSI is presented. A theoretical model for solving the focal length of the measured lens from the curvature radius of the wavefront was derived. We also proposed a novel algorithm and subsequently developed a dedicated hardware platform and a corresponding software package for its real-time implementation. Different sets of repeated measurement experiments were carried out for two convex lenses with symmetrical and asymmetrical structures, a large-scale concave lens, and a microlens array, to verify the measurement uncertainty and robustness of the QWLSI measurement system. The expanded uncertainty was also analyzed and determined as 0.31 mm (k = 1.96, normal distribution). The results show that the proposed QWLSI measuring system possesses good performance in measuring the focal lengths of different kinds of lenses and can be widely used in fields such as advanced optics manufacturing. Full article

This work focuses on the development of a patient-specific transient CFD–FSI numerical model combined with the Time-Averaged Entropy Generation Rate (TAEGR) to predict hemodynamic parameters in the thoracic aorta, including the Oscillatory Shear Index (OSI) and the Time-Averaged Wall Shear Stress (TAWSS). While arterial blood flow can be modeled assuming either rigid or elastic arterial walls, the effect of wall compliance on these parameters, particularly on TAEGR, remains insufficiently characterized. Moreover, the interpretation of established indicators is not unique, as regions of vascular relevance may correspond to either high or low values of OSI and TAWSS. The proposed approach aims to identify symmetry and asymmetry in shear stress and entropy generation within the arterial wall, which are closely associated with the development of atherosclerotic plaque. Four aortas from clinical patients were analyzed using the proposed numerical framework to investigate blood flow behavior. The results revealed regions with high values of the hemodynamic parameters (OSI > 0.15, TAWSS ≥ 2 Pa, and TAEGR ≥ 20 $\mathrm{W}/{\mathrm{m}}^3\mathrm{K}$) predominantly located in the vicinity of the upper arterial branches. These regions, referred to as critical zones, are considered prone to the development of cardiovascular diseases, particularly atherosclerosis. The proposed numerical model provides a reliable qualitative framework for assessing symmetry and asymmetry in aortic blood flow patterns under different surgical conditions. Full article

This study focuses on the calibration and verification of a large-scale coupled numerical model to simulate the complex hydrodynamic–wave–sediment transport processes in the coastal and estuarine regions of the Mekong River Delta (MRD), Vietnam. Using the MIKE 21/3 modeling system, the research integrates Hydrodynamics (HD), Spectral Wave (SW), and Mud Transport (MT) modules across a computational domain of 270 × 300 km. The models were rigorously tested using field measurement data from three distinct periods: May 2004 (dry season calibration), September 2017 (first verification), and June 2024 (second verification). The results from the hydrodynamic model demonstrated high accuracy in predicting water levels, with the average Root Mean Square Error (RMSE) values ranging between 4.4% and 5.8%. The wave spectral model showed reliable performance, with the average RMSE values for wave height ranging from 15.1% to 18.0%. Furthermore, the Mud Transport module successfully captured suspended sediment concentrations (SSC), yielding average RMSE values between 26.0% and 32.1% after the fine-tuning of site-specific parameters such as critical shear stress for erosion and deposition. The study highlights the critical importance of utilizing site-specific sedimentological parameters to accurately predict morphological changes in highly dynamic estuarine environments. This validated model provides a robust tool for assessing coastal erosion and developing protection measures in regions that are increasingly vulnerable to climate change and human activities. Full article

Low-level wind shear (LLWS) is a critical aviation hazard that can cause flight disruptions and pose significant safety risks. Despite its operational importance, forecasting LLWS remains a challenging task. To improve LLWS prediction, probabilistic forecasting approaches based on ensemble prediction systems are increasingly used. In this study, LLWS forecasts were generated using a high-resolution, limited-area ensemble model, which allows for the representation of forecast uncertainty and variability in atmospheric conditions. Forecasts for Incheon International Airport were generated twice daily over the period from December 2018 to February 2020. To enhance forecast skill, statistical post-processing techniques, specifically Ensemble Model Output Statistics (EMOS), were applied and calibrated using Aircraft Meteorological Data Relay (AMDAR) observations. Prior to calibration, rank histograms were examined to assess the reliability and distributional consistency of the ensemble forecasts. Forecast performance was evaluated using commonly applied probabilistic verification metrics, including the mean absolute error (MAE), the continuous ranked probability score (CRPS), and probability integral transform (PIT). The results indicate that ensemble forecasts adjusted through statistical post-processing generally provide more reliable and accurate predictions than the unprocessed raw ensemble outputs. Full article

High rock slopes are extensively distributed in areas of major engineering constructions, such as transportation infrastructure, hydraulic projects, and mining operations. The stability and failure evolution mechanism during their multi-stage excavation process have consistently been a crucial research topic in geotechnical engineering. In this paper, a series of two-dimensional rock slope models, incorporating various combinations of slope height and slope angle, were established utilizing the Discrete Element Method (DEM) software PFC2D. This systematic investigation delves into the meso-mechanical response of the slopes during multi-stage excavation. The Parallel Bond Model (PBM) was employed to simulate the contact and fracture behavior between particles. Parameter calibration was performed to ensure that the simulation results align with the actual mechanical properties of the rock mass. The research primarily focuses on analyzing the evolution of displacement, the failure modes, and the changing characteristics of the force chain structure under different geometric conditions. The results indicate that as both the slope height and slope angle increase, the inter-particle deformation of the slope intensifies significantly, and the shear band progressively extends deeper into the slope mass. The failure mode transitions from shallow localized sliding to deep-seated overall failure. Prior to instability, the force chain system exhibits an evolutionary pattern characterized by “bundling–reconfiguration–fracturing,” serving as a critical indicator for characterizing the micro-scale failure mechanism of the slope body. Full article

Tissue engineering is a multidisciplinary field that aims to address tissue and organ failure by integrating scientific, engineering, and medial expertise. Gelatin is valued in this field for its biocompatibility; however, it faces thermal and mechanical weaknesses that limit its biomedical utility. This work proposes a strategy for improving gelatin properties by fabricating semi-interpenetrating polymer networks via in situ Diels–Alder crosslinking within gelatin colloidal solutions. Ten systems with variable polymer concentrations (2–4%) and crosslinking degrees (2–5%) were prepared and characterized. Rheological analysis revealed that elastic modulus, zero-shear viscosity, and complex viscosity were substantially enhanced, being especially dependent on the crosslinking degree, while critical strain values mostly depended on gelatin concentration. The incorporation of a synthetic Diels–Alder-crosslinked network also improved the thermal stability of gelatin hydrogels, particularly at physiological temperatures. Additionally, these systems exhibit favorable buoyancy, swelling and biodegradation profiles. Collectively, the resultant hydrogels are cytocompatible, solid-like, and mechanically robust, allowing for further tunability of their properties for specific biomedical uses, such as injectable matrices, load-bearing scaffolds for tissue repair, and 3D bioinks. Full article

Background: Soft tissue tumors (STTs) represent a heterogeneous group of rare lesions that frequently mimic bone sarcomas in both clinical and radiologic appearance. Accurate differentiation between benign and malignant lesions is critical for appropriate treatment planning, yet conventional imaging often remains inconclusive. Ultrasound (US) elastography, a non-invasive method that quantifies tissue stiffness, has recently emerged as a potential adjunct to standard musculoskeletal imaging for improving diagnostic confidence and guiding biopsy. Methods: A systematic review was conducted in accordance with PRISMA guidelines. PubMed, Web of Science, and Cochrane Library were searched using the keywords “elastography”, “sonoelastography”, and “soft tissue tumor”. Twelve studies encompassing 1554 patients met the inclusion criteria, assessing the diagnostic accuracy of strain, compression, and shear wave elastography for differentiating benign from malignant STTs. Results: Elastography alone demonstrated limited specificity when used as a single diagnostic technique. However, its integration into multiparametric ultrasound approaches—combining grayscale, Doppler, and contrast-enhanced imaging—significantly improved diagnostic performance. Several studies reported sensitivities and specificities exceeding 85% when elastographic parameters were incorporated into composite diagnostic scores. Conclusions: Ultrasound elastography shows promise as a quantitative imaging biomarker for the preoperative evaluation of musculoskeletal tumors, particularly in distinguishing soft tissue from bone-related lesions. Although not a substitute for histopathological confirmation, its application within multimodal ultrasound protocols may reduce unnecessary biopsies, enhance diagnostic accuracy, and facilitate tailored management of bone and soft tissue sarcomas. Full article

Delamination in fibre-reinforced polymer composites is a critical failure mechanism that can ultimately lead to a catastrophic failure. To characterise in-plane shear delamination (Mode II), several test setups have been proposed in the literature, with the End-Loaded Split (ELS) test being the most suitable for applications that require stable crack propagation (ISO 15114). This manuscript focuses on studying Mode II fatigue delamination in unidirectional carbon fibre-reinforced laminates using the ELS configuration. Experimental tests with varying displacement ratios and different initial energy levels were conducted to capture a wide range of stable crack propagation scenarios. To complement these experimental efforts, a numerical model based on cohesive zone models (CZM) was implemented in Abaqus, utilising a user-defined material subroutine (UMAT). The numerical results closely align with the experimental data, validating the model’s predictive capabilities. This combined approach deepens the understanding of Mode II fatigue delamination and provides a strong framework for designing and analysing composite structures. Full article

Tunnels have significantly expanded human activity spaces and alleviated urban congestion and environmental pollution on the surface. However, fires and associated smoke propagation in tunnels pose common and critical challenges in underground space utilization. Previous studies have primarily focused on smoke control under standard atmospheric conditions, emphasizing isolated parameters such as jet velocity or heat release rate (HRR), while overlooking key factors like environmental pressure and fire source proximity that influence smoke buoyancy and containment efficacy. One of the key problems remains unsolved: the comprehensive mechanisms governing transverse air curtain performance in variable-pressure and proximity scenarios. This study utilized Fire Dynamics Simulator (FDS6.7.1) software to conduct numerical simulations, aiming to elucidate the underlying incentives and explore the phenomena of smoke–thermal interactions. The analysis systematically evaluates the influence of four critical parameters: HRR (1–15 MW), fire-to-curtain distance (5–95 m), air curtain jet velocity (6–16 m/s), and ambient pressure (40–140 kPa). Results show that (1) jet velocity emerges as the dominant factor, with exponential enhancement in thermal containment efficiency at velocities above 10 m/s due to intensified shear forces; (2) escalating HRR weakens isolation, leading to disproportionate downstream temperature rises and diminished efficacy; (3) fire proximity within 10 m disrupts curtain integrity via high-momentum smoke impingement, amplifying thermal gradients; and (4) elevated ambient pressure dampens smoke buoyancy while augmenting air curtain momentum, yielding improved containment efficiency and reduced temperatures. This paper is helpful for the design and operation of thermal applications in underground infrastructures, providing predictive models for optimized smoke control systems. The contour maps reveal the field-distribution trends and highlight the significant influence of the air curtain and key governing parameters on the thermal field and smoke control performance. This work delivers pivotal theoretical and practical insights into the advanced design and optimization of aerodynamic smoke control systems in tunnel safety engineering Full article

Adhesive joint failure remains a critical limitation in the manufacturing of large wind turbine blades, where reliable and reproducible surface preparation methods are required at an industrial scale. This study systematically evaluates the effect of peel ply-induced surface morphology and chemistry on the adhesion performance of glass fiber-reinforced polymer (GFRP) laminates, explicitly examining the relationship between wettability and bonding strength. Five surface conditions were generated during vacuum-assisted resin infusion using different commercial and proprietary peel plies and a smooth mold surface. Despite significant differences in contact angle and surface energy, lap shear testing revealed no significant relationship between wettability and joint strength. Instead, surface roughness-driven mechanical interlocking and adhesive–substrate compatibility dominated performance. Compared to the smooth mold surface, twill-type peel ply–modified adherends increased shear strength by up to 3.9×, while other commercial types of peel-plies presented strength improvements between 2.7 and 3.3×. More compatible adhesive–polymer resin systems exhibited a combination of cohesive and adhesive failures, with no clear dependence on surface roughness. In contrast, when the adhesive is less compatible with the substrate, surface roughness significantly affects the adhesive response, with adhesive failure predominating. The adhesive application temperature showed no measurable effect for practical industrial use. These findings demonstrate that wettability alone is not a reliable predictor of adhesion performance for this class of substrates and confirm peel ply surface modification as a robust, scalable solution for industrial wind blade bonding. Full article

During long-term storage, polymer-bonded explosives (PBXs) undergo thermal-oxidative aging due to environmental factors such as moisture and oxygen, which leads to a critical determinant of explosive performance. This study employed molecular dynamics simulations to investigate the impact of thermal-oxidative aging of butadiene rubber and paraffin wax composites used in the RDX-based polymer-bonded explosives. The interfacial binding energy between the binder system and RDX crystalline surfaces was evaluated. The cohesive energy density (CED), fractional free volume (FFV), mean square displacement (MSD), and mechanical properties were analysed to probe the mechanism of aging for butadiene rubber (BR) and paraffin wax (PW). The results demonstrate that, with progressive aging, the oxidation-induced chain scission of BR molecules leads to an increase in both the CED and solubility parameter of the BR/PW system. Initial oxidation reduces the FFV of the BR/PW system from 0.183 to 0.166, while subsequent chain scission causes the FFV to rise to 0.175. In terms of mechanical properties, the BR/PW system exhibits ductile behavior, with reductions in both Young’s modulus and shear modulus as aging progresses, leading to decreased material stiffness. For the RDX/binder system, oxidation enhances the interfacial binding energy, whereas chain scission in BR leads to a slight decline in the binding energy. Overall, oxidation exerts a more pronounced influence on the interfacial binding energy compared to chain scission. Full article

The adverse-pressure-gradient (APG) severely disrupts the inherent symmetry of the turbulent boundary layer (TBL). The universal physical behavior and scaling laws observed under zero-pressure-gradient (ZPG) conditions are significantly altered under APG, thereby challenging the predictive accuracy of turbulence models. To address this breakdown, we develop a generalized mixing length model by incorporating APG effects into a baseline ZPG framework. The model is directly constructed using APG-extended wall laws—superposing the log law and the half-power law for the mean velocity—and the logarithmic decay law for the total shear stress. Validated against ten databases spanning the entire APG region, various Reynolds numbers, and both equilibrium and non-equilibrium flows, the model demonstrates accurate predictions for both mixing length and mean velocity profiles. The key achievements are as follows: (i) a significant simplification of model parameters, wherein the inner model can be reduced to a parameterless scaling law, while outer parameters were reduced from five to two; and (ii) the unification of predictions across the entire APG range. This work demonstrates that consistent modeling of APG effects bridges slight and strong APGs, enabling a unified description of the APG region before separation and providing critical insights for turbulence modeling. Full article

Background: Accurate intraoperative assessment of sentinel lymph node (SLN) status is critical for staging and guiding surgical management in gynaecological malignancies. Frozen-section histopathology remains the gold standard, but it is time-consuming and resource-intensive. Shear-wave elastography (SWE) quantifies tissue stiffness in real time and may offer a rapid alternative. Methods: In this prospective single-centre study, 63 women (median age 62 years) undergoing primary surgery with sentinel lymph node biopsy (SLNB) for endometrial, cervical, vulvar, or early ovarian carcinoma were enrolled. A total of 172 SLNs were excised, submerged in coupling gel, and scanned ex vivo using a 9 MHz linear probe. Results: A total of 172 SLNs underwent SWE (mean 2.7 nodes/patient). Endometrial primaries accounted for 58% of nodes, mostly retrieved by robotic-assisted surgery (71.8%). Node dimensions were significantly larger in malignant lesions for sonographic (long-axis: 13.02 ± 3.31 mm vs. 10.80 ± 3.28 mm; p = 0.002) and pathological long-axis measurements (11.45 ± 2.83 mm vs. 9.75 ± 2.61 mm; p = 0.004). Mean SWE velocities were similar between groups (1.381 ± 0.307 vs. 1.343 ± 0.236 m/s; p = 0.541). Histopathology identified metastases in 18% of SLNs, comprising macrometastases (7%), micrometastases (5%), and isolated tumour cells (6%). Conclusions: Although ex vivo SWE is rapid, reproducible, and integrates seamlessly into the sterile field, stiffness measurements alone lack sufficient discriminatory power for SLN staging in gynaecological cancers. Future research should focus on three-dimensional SWE, advanced radiomic analyses, and machine-learning algorithms to improve the detection of low-volume metastatic disease. Full article

Efficient soil conditioning is critical for controlling the mechanical behavior of sandy muck in earth pressure balance (EPB) shield tunneling. This study investigates the undrained shear response of sand conditioned with slurry, a newly developed bubble–slurry, and foam under vertical stresses of 0–300 kPa, considering different injection ratios and shear rates. Under atmospheric pressure, conditioning reduces both peak and residual shear strengths by more than 90% compared with untreated sand. Foam- and bubble–slurry-conditioned sands show stable strength within 6 h; after 24 h, peak strength increases from 0.39 to 4.67 kPa for foam-conditioned sand but only from 0.67 to 0.84 kPa for bubble–slurry-conditioned sand. Shear strength increases nearly linearly with shear rate, especially for residual strength. Pore-scale mechanisms were interpreted by considering bubble proportion and size, pore-fluid rheology, and surface tension. Rheology governs whether dynamic or viscous resistance dominates at different shear rates, while surface tension influences stress transmission through bubble stability and interparticle lubrication. The void ratio range of e/e_max = 1.00–1.36 was identified as achieving low shear strength and good flowability. Field application in Jinan Metro Line R2 confirmed that combined conditioning (25% foam + 13% slurry) reduced cutterhead torque by about 37% without spewing. Full article

This study investigates the impact of the expansion ratio on combustion oscillation phenomena and their driving mechanisms in a solid-fuel ramjet (SFRJ) through experimental and numerical simulations. By analyzing flow characteristics, combustion oscillations at varying expansion ratios, heat release patterns, and species distribution within the engine, the following key conclusions are drawn: Ground tests revealed first-order pressure oscillations with a dominant frequency of approximately 600 Hz, exhibiting a half-wavelength oscillation pattern. As the expansion ratio increased from 1.75 to 2.25, the amplitude of the first-order oscillation increased by 21%, from 1.89 kPa, while the dominant frequency initially rose and then decreased, peaking at an expansion ratio of 2. The shear-induced downstream of the step was identified as a critical factor influencing heat release and acoustic pressure oscillations in the combustion chamber, which led to periodic unstable heat release that amplified combustion oscillation amplitudes. The numerical results show that the periodic motion of vortices induced by flow shear downstream of the sudden expansion step causes oscillations in the temperature distribution on the propellant surface, which is one of the key factors contributing to combustion instability and pressure oscillations. When the expansion ratio is increased to 2.0 and 2.25, the dominant frequency of pressure oscillations increases by 15.2% and 13.2%, respectively, while the amplitude rises by 7.9% and 30%, respectively. The vortice development blurs the oxygen-rich and fuel-rich zones, enhancing the mixing of oxygen and fuel-rich gases and exacerbating the instability of heat release. Larger expansion ratios further extended the axial range of unstable species distribution, increasing nonuniformity within the combustion region. Full article