Search Results (122)

The realization of broad-wavelength tunability of the structural color in Double layered Cholesteric Liquid Crystal Elastomers (DCLCEs), along with good flexibility and processability, presents a significant challenge. This research introduces a facile and effective fabrication technique, Solvent Evaporation-Induced Self-Assembly (SEISA), for the production of DCLCEs exhibiting broad wavelength tunability, superior flexibility, and robust mechanical characteristics. Focusing on initial color tuning, bubble defect minimization, UV photopolymerization, and coating procedures, this research systematically optimizes the fabrication process through experimental investigation of factors like chiral dopant amount, temperature, UV exposure duration, coating thickness, and speed. The method enabled the successful fabrication of DCLCEs with uniform and controllable coloration, demonstrating the effectiveness of this controlled synthesis approach in significantly enhancing structural color features. Upon stretching to 2.8 times its original length, the center wavelength shifted from 613 nm to 404 nm, yielding a tunable bandwidth of up to 209 nm across the visible spectrum. Full article

In the continuous casting of special steel blooms, low casting speeds result in slow renewal of the molten steel surface in the mold, adversely affecting mold flux melting and liquid slag layer supply, which may lead to surface cracks, slag entrapment, and breakout incidents. To optimize the flow and heat transfer behavior in the mold, a three-dimensional numerical model was developed based on the VOF multiphase flow model, $k-ϵ$ RNG turbulence model, and DPM discrete phase model, employing the finite volume method with SIMPLEC algorithm for solution. The effects of casting speed, argon injection rate, and mold flux properties were systematically investigated. Simulation results demonstrate that when casting speed increases from 0.35 m·min⁻¹ to 0.75 m·min⁻¹, the jet penetration depth increases by 200 mm and meniscus velocity rises by 0.014 m·s⁻¹. Increasing argon flow rate from 0.50 L·min⁻¹ to 1.00 L·min⁻¹ leads to 350 mm deeper bubble penetration, 10 mm reduction in jet penetration depth, 0.002 m·s⁻¹ increase in meniscus velocity, and decreased meniscus temperature due to bubble cooling. When mold flux viscosity increases from 0.2 Pa·s to 0.6 Pa·s, the average liquid slag velocity decreases by 0.006 m·s⁻¹ with a maximum temperature drop of 10 K. Increasing density from 2484 kg·m⁻³ to 2884 kg·m⁻³ results in 0.005 m·s⁻¹ higher slag velocity and average 8 K temperature reduction. Comprehensive analysis indicates that optimal operational parameters are casting speed 0.35–0.45 m·min⁻¹, argon flow ≤ 0.50 L·min⁻¹, mold flux viscosity 0.2–0.4 Pa·s, and density 2484–2684 kg·m⁻³. These conditions ensure more stable flow and heat transfer characteristics, effectively reducing slab defects and improving casting process stability. Full article

The existence of bubble defects in ultra-low expansion quartz glass will affect the optical properties and mechanical strength of the material. The present paper proposes a novel defect characterization method based on ultrasonic nondestructive testing. The simulation model of bubble defect detection in ultra-low expansion quartz glass was established using numerical simulation technology, and experimental verification was carried out. The propagation mechanism of the ultrasound and its interaction with bubble defects were then analyzed. The results showed that the shape of the reflected wave was similar to that of the corresponding defect, and the scattering of the reflected wave was different due to the different curvature radius of the defect interface. The acoustic scattering characteristics of the circular defect were more obvious than those of the elliptical defect. Finally, an analysis of the interaction between different depth defects and different size defects and the ultrasound was conducted, leading to the conclusion that the relative amplitude of the defect echo corresponding to a 6 mm probe diameter shows a monotonic decreasing relationship with the defect depth, and there is also a monotonic corresponding relationship between the relative amplitude of the defect echo and the size of bubble defect. Therefore, it can be concluded that the relative amplitude of the defect echo can be used to characterize the size of the bubble defect. This study not only analyses the interaction between defects and ultrasound but also provides a quantitative characterization of defects using the proposed method. Full article

The ejection of disturbed surfaces under multiple shocks is a critical phenomenon in pyrotechnic and inertial confinement fusion. In this study, the elastic–plastic ejection from grooved aluminum surfaces under double supported shocks was investigated using the SPH method. A spallation region developed at the bottom of the bubble during the first ejection, and the subsequent second ejection comprised three distinct components: low-density; high- and medium-velocity ejecta; and high-density, low-velocity ejecta. Recompression of the spallation material generated high- and medium-velocity ejecta, resulting in a limited second ejecta mass. The significant increase in the defect area of the bubble and the convergence of the first ejecta generated low-velocity ejecta, resulting in a substantial increase in the second ejecta mass. The shock pressure threshold required for the second ejection was significantly reduced compared with the first ejection. The second ejecta mass increased with shock pressure, but the increase rate gradually decreased, primarily affecting the low-velocity ejecta. The time interval between shocks primarily influenced the second ejection, driven by the evolution of the spallation region at the bottom of the bubble and the convergence of the first ejecta. The second ejecta mass increased and asymptotically approached a constant value with increasing time intervals. Full article

The FLASH-COMP project aims to introduce novel inspection and monitoring technologies to develop a digital solution to predict defects during manufacturing, aiming to reach a zero-waste approach in composites manufacturing. Particularly, it’s studied the integration of two different Fiber Optic Sensor (FOS) technologies: Fiber Bragg Grating (FBG) and distributed All Grating Fiber (AGF^®), to retrieve relevant data during the preforming stage and later resin infusion process for aero-space materials. During the study, both FOS technologies were introduced into the materials, varying process conditions and the introduction of some artificial defects to evaluate the sensors response to correlate them after with their signals. Both systems can retrieve relevant information during the process such as vacuum, leaks and temperature changes, presence of voids and air bubbles, detection of dry zones, and resin flow monitoring. Further developments have to be focused on the scalability in the implementation, since FOS are fragile to handle and need specific training to use it in a more industrial field. Full article

Insulation pull rods used in gas-insulated switchgear (GIS) inevitably contain the micro defects generated during production. The intelligent identification method, which requires large datasets with a balanced distribution of defect types, is regarded as the prevailing way to avoid insulation faults. However, the number of defective pull rods is limited, and the occurrence of different types of defects is highly imbalanced in actual production, leading to poor recognition performance. Thus, this work proposes a data preprocessing method for the insulation pull rod defect feature dataset. In this work, the YOLOv5s algorithm is used to detect defects in insulation pull rod images, creating a dataset with five defect categories. Two preprocessing methods for impurities and bubbles are introduced, including copy–paste within images and bounding box corrections for hair-like impurities. The results show that these two methods can specifically enhance small-sized defect targets while maintaining the detection performance for other types of targets. In contrast, the proposed method integrates copy–paste within images with Mosaic data augmentation and corrects bounding boxes for hair-like impurities significantly improving the model’s performance. Full article

Superconducting radio-frequency niobium cavities processed using buffered chemical polishing (BCP) sometimes show typical W-shaped pits on their surface, which may greatly limit their performance. However, the causes of such pits and effective solutions are not fully understood. In this study, we reproduced the formation of W-shaped pits on the cavity surface through niobium sample BCP experiments, directly observed the sample surface’s evolution during the polishing process and the polished surface’s morphology, and analyzed the cause of W-shaped pits in detail: the formation and attachment of bubbles on the niobium surface during the BCP process. Then, we systematically investigated the effects of different process parameters on the bubbles and pits, including the acid ratio, temperature, and flow rate. We also investigated how the formation of bubbles and pits was affected by the Nb facing orientation and grain size. This study provides insights into the mechanisms by which bubbles and W-shaped pits are formed on niobium surfaces, and highlights possible directions for reducing pit defects in Nb cavities processed using BCP treatment. Full article

A creative industry company producing resin-based decorative lamps is facing quality issues due to production defects. This study applied the Six Sigma and FMEA methods to identify controls, analyze causes, and propose improvements. Six Sigma reduces defects using the DMAIC approach, while FMEA assesses risks through the Risk Priority Number (RPN). The analysis showed a DPMO of 14,587.89 and a sigma level of 3.7, aligning with industry standards in Indonesia. Key defects included bubbles (57%), uneven surfaces (24%), and cracks (19%). Suggested improvements included training, production evaluations, rotary casting tools, safety measures, and enhanced cleanliness in the sanding area. Full article

Industrial production today increasingly prioritizes sustainability, emphasizing not only efficiency but also minimizing environmental and social impacts. Quality control is key in steel production. The continuous casting process is crucial, as early defect detection can lower costs and prevent unnecessary material use, thereby conserving energy and raw materials. Eliminating defects early reduces the need for costly reworking, saving resources and reducing equipment wear. Additionally, this defect prevention supports efficiency in later steps, like rolling, benefiting overall energy and material consumption. During this research, we identified several parameters whose influence we analyzed on the surface quality of deep-drawn steel. The research confirmed that, for example, the casting speed has a significant influence on the occurrence of surface defects, while, for example, the final bubbling had no statistically significant effect on the surface quality. From a sustainability perspective, monitoring and optimizing key production parameters, like the casting speed, is essential, as improper speeds can cause surface defects that risk the functionality of the final products. By optimizing these parameters, it is possible not only to reduce the risk of product failure but also to contribute to the long-term sustainability of the entire production process, reducing waste and fostering a more considerate approach to natural resources. Full article

Background and Clinical Significance: Pulmonary hypertension (PH) is characterized by an increase in mean pulmonary arterial pressure and pulmonary vascular resistance. It is frequently encountered in patients with significant intracardiac shunts, often necessitating the implementation of a closure device or surgical correction. Nevertheless, the occurrence of a concomitant atrial septal defect (ASD) with a right-to-left shunt inducing left ventricular dysfunction is a rare phenomenon. Case Presentation: A 69-year-old female patient with a history of heart failure (with preserved ejection fraction) and end-stage renal disease on hemodialysis presented to an outside facility, with syncope and hypoxia. She was recently diagnosed with severe pulmonary hypertension (measuring 86 mmHg). Right heart catheterization (RHC) revealed precapillary pulmonary hypertension (88/37/54 mmHg), prompting the initiation of intravenous epoprostenol. Nevertheless, the patient was persistently hypoxic, raising the possibility of a concomitant diagnosis. Upon review of the prior echocardiogram, which included a bubble study, an intracardiac shunt was identified. It was hypothesized that a combination of right ventricular failure and the right-to-left shunt resulting from the ASD contributed to the persistent hypoxemia. In light of this, prostacyclin therapy was continued alongside adjunctive vasopressors, resulting in clinical stabilization. The patient was eventually discharged with a treatment regimen that included subcutaneous Treprostinil. Conclusions: It is important to recognize that the consequences of PH are extensive, and that a rare yet significant etiology for persistent hypoxemia may be attributed to right-to-left shunting. Full article

Ultrasonic melt processing (UMP) has garnered significant attention from both academic and industrial communities as a promising solution to critical challenges in the metal casting industry. This technique offers a clean, environmentally friendly, and energy-efficient approach to improving melt quality and achieving structural refinement. However, due to the opaque nature of metals, understanding the fundamental mechanisms governing the interactions among ultrasonic bubbles, acoustic streaming, and the melt remains still challenging. This review traces the evolution of UMP research, from its inception in the mid-20th century to recent advancements, with particular emphasis on the application of state-of-the-art synchrotron X-ray imaging and computational modeling. These approaches have been instrumental in unraveling the complex, multiscale dynamics occurring across both temporal and spatial scales. Key findings in various metallic alloy systems are critically reviewed, focusing on new insights into cavitation bubbles, acoustic streaming, and the interactions of growing solid phases in different alloys. Additionally, the review discusses the resulting phenomena, including grain refinement, fragmentation, and the mitigation of solidification defects, in detail. The review concludes by identifying critical research gaps and emerging trends, underscoring the indispensable role of in situ studies and robust theoretical frameworks in advancing UMP. These developments are poised to reshape the future of innovation in materials science and engineering. Full article

Microbubbles have been applied in various fields. In the mercury targets of spallation neutron sources, where cavitation damage is a crucial issue for life estimation, microbubbles are injected into the mercury to absorb the thermal expansion of the mercury caused by the pulsed proton beam injection and reduce the macroscopic pressure waves, which results in reducing the damage. Recently, when the proton beam power was increased and the number of injected gas bubbles was increased, unique damage morphologies were observed on the solid–liquid interface. Detailed observation and numerical analyses revealed that the microscopic pressure emitted from the gas bubbles contracting is sufficient to form pit damage, i.e., the directions of streak-like defects which are formed by connecting the pit damage coincides with the direction of the gas bubble trajectories, and the distances between the pits was understandable when taking the natural period of gas bubble vibration into account. This indicates that gas microbubbles, used to reduce macroscopic pressure waves, have the potential to be inceptions of cavitation damage due to the microscopic pressure emitted from these gas bubbles. To completely mitigate the damage, we have to consider the two effects of injecting gas bubbles: reducing macroscopic pressure waves and reducing the microscopic pressure due to bubble dynamics. Full article

Aiming to address the problems of uneven brightness and small defects of low contrast on the surface of lithium battery electrode (LBE) coatings, this study proposes a method for detection and identification of coatings defects in LBEs based on an improved Binary Tree Support Vector Machine (BT-SVM). Firstly, adaptive Gamma correction is applied to enhance an image, and an improved Canny algorithm combined with morphological processing is used to accurately detect the defect regions. Secondly, the shape and grayscale features of the defects are extracted from the connected defect areas, and these features are then fused and normalized. Finally, a BT-SVM multi-class classification model is constructed, with the Whale Optimization Algorithm (WOA) employed to assist in hyperparameter tuning. The experimental results show that the proposed method can effectively detect and identify five common types of defects in the coating of LBEs, including scratches, bubbles, metal leakage, particles, and decarbonization, with an average detection accuracy of 94.4% and an average detection time of less than 0.2 s, meeting the real-time detection requirements for online defect inspection. After Whale Optimization, the BT-SVM defect recognition model achieves an average recognition accuracy of 98.7%, significantly enhancing the performance of current defect detection technologies for LBE coatings. Full article

Laser–electrochemical hybrid machining (LECM) is promising in the processing of thin-wall parts, which avoids problems such as the weak stiffness of structures and thermal defects. However, while most studies focus on precision machining via LECM, few investigate the potential of this technique in macro-area processing. In this paper, the synergistic effects on the coupling of thermal field and electrochemical field on bulk material removal mechanisms in the LECM of additively manufactured Ti6Al4V are comprehensively analyzed experimentally and theoretically. According to the experimental results, LECM improved the material removal rate (MRR) by up to 28.6% compared to ECM. The induction of the laser increases local heating, accelerating the temperature rise of the electrolyte, eventually promoting the electrochemical reaction. The hydrogen bubble flow promotes overall heat convection between the electrode and workpiece, which facilitates the removal of the facial precipitates and increases the efficiency of electrochemical dissolution. Higher voltages and laser powers promote the formation of hydrogen bubble flow; meanwhile, they also aggravate laser energy scattering, limiting the overall machining efficiency. Additionally, laser irradiation causes the ablation and rupture of hydrogen bubbles, which weakens the bubble flow effect and ultimately decreases the material removal efficiency. This study reveals the underlying mechanisms of the joint effects of the laser field and electrical field in LECM, and the findings can provide valuable insights for the optimization of LECM parameters in industrial applications. Full article

A variety of NiP-TiC-SiC nanocomposite coatings were deposited to acrylonitrile–butadiene–styrene (ABS) substrates at varying plating periods and bath temperatures using electroless plating. A field emission scanning electron microscope (FESEM) demonstrates the production of various coating morphologies. Morphology analysis of the deposit coatings shows homogenous, compact, and nodular structured coatings free of any apparent defects in most deposition conditions, except at extra high-temperature deposition baths, some gas bubbles under the coating layers were seen. The patterns of X-ray diffraction (XRD) illustrate nickel peaks at 44.5 which relates to Ni (111). Energy-dispersive X-ray spectroscopy (EDX) data show that the coating’s main constituents are nickel, phosphorus, and nanoparticles. According to the results of the contact angle test, the potentiodynamic polarization, and the impedance spectroscopy (EIS) tests conducted in (3.5%) of NaCl by weight at (25 °C), the nanocomposite coating that was created at 90 min and 75 °C exhibited the best hydrophobic qualities and corrosion resistance. The coating formed at 30 min and 75 °C illustrates the best hardness value. The adhesion force was calculated using the ASTM D 3359 method (B). The findings demonstrate that the coating made under the following deposition conditions, 30 min at 75 °C, 30 min at 95 °C, and 90 min at 75 °C, produces the best bonding strength between the coating and ABS substrate (standard classification 5B); however, the complete gas bubble rejection process from the substrate is rendered difficult by deposition times longer than 30 min in a bath over 85 °C, which decreases the adhesion between NiP-TiC-SiC and the acrylonitrile–butadiene–styrene substrate. The wear rate shows a direct relationship with the coefficient of friction rather than hardness, and the coated prepared at 90 min at 75 °C offers a lower wear rate and coefficient of friction. Full article