Metal Industries Research & Development Centre

This paper discusses an <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> control problem as observer-based delay-dependent stability of time-varying stochastic systems represented by Linear Parameter Varying (LPV) description. For the control problem, the integral delay terms in the derivatives are dealt with a proposed novel extended reciprocal convex inequality. Based on the proposed inequality, some extra matrices are created to decrease the conservatism of the developed stability criterion. Furthermore, a Lyapunov-Krasovskii Function (LKF) possessing a parameter-dependent positive definite matrix and the integral term is utilized for the stability criterion. Besides, an additive inequality is proposed to constrain the bounds of the state and estimated error to the external disturbance for achieving <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> performance. Through the proposed lemma, the indexes for the state and the error can be individually assigned to avoid the high-gain response. Based on the convex calculation, the proposed criterion can be directly utilized to design an observer-based controller so that the delay-dependent stability and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i><sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> performance of the closed-loop system is achieved. And then, some numerical simulations are used to show the contributions of this paper.

• Meta-corrector reduces focal spot from 5.68 μm to 4.03 μm, near diffraction limit • Smooth phase profile of meta-corrector simplifies fabrication and enhances efficiency • Integration with Cooke triplet enables compact, high-performance imaging systems We demonstrate a hybrid optical system that integrates a meta-corrector with a conventional Cooke triplet to improve focusing performance significantly. In this study, the Cooke triplet offers primary focusing, while the meta-corrector compensates for spherical aberration with a smooth phase profile. This design enhances spatial resolution and simplifies fabrication. Experimental results show that the focal spot size decreases from 5.68 μm to 4.03 μm, approaching the diffraction-limited Airy radius of 4.11 μm, validating the effectiveness of the meta-corrector. This approach provides a promising pathway for enhancing traditional lens systems and can be extended to advanced commercial optics for compact, high-performance imaging.

This study presents a novel DBD-based sterilization system for the on-site treatment of small medical devices in local clinics. In a specially designed chamber, potent antimicrobial agents-namely, ozone and hydroxyl radicals-are generated to inactivate microorganisms. The ability to sterilize is verified through two commercial chemical sterilization indicators. This study also describes the development of a disposable chemical indicator that can monitor and verify the sterilization process in real time. The system has been shown to achieve a qualified sterilization within six minutes, which is approximately 10% of the process time compared to that of commercial facilities. The self-developed indicator exhibits a significant color change during the sterilization process, showing that this self-developed indicator is potentially a low-cost and disposable indicator for plasma sterilization.

Clinching is an advanced cold joining method for sheet metals that eliminates the need for additional materials to assemble parts. It involves the plastic deformation of metal sheets to create a joint. The process relies on the interaction between a punch and a die, without the use of any coatings or additives. The punch applies a predetermined force, causing the metal sheets to be pressed through the die cavity and filling the groove, resulting in an interlock point. The final shape of the clinched joint is determined by the tool's geometry. In this study, we investigated the clinching process using segmented die and finite element (FE) methods. The numerical analysis was conducted using LS-DYNA software on AA5052 aluminium and mild steel sheets. Additionally, we compared the compression between spot welding and clinching. The results of our study revealed that various process parameters significantly influence the clinching process, including the bottom thickness, neck thickness and interlock length. Among these factors, die height emerged as the primary influencing factor. Furthermore, we found that the energy absorption and stiffness of the clinched joints were lower compared to those of spot welding.

Nanoscale amorphous calcium phosphate (ACP) exhibits superior bioactivity, degradability, and osteoblast adhesion compared to hydroxyapatite (HAp), making it a promising bioactive ceramic material for bone regeneration applications. This study explores the integration of ACP as a bioactive additive in polylactic acid/polycaprolactone (PLA/PCL) composites. Nanoscale ACP powder was synthesized through low-temperature wet chemical methods without additional reagents. The composite, consisting of 10 wt.% ACP, 80 wt.% PLA, and 20 wt.% PCL, achieved optimal tensile strength (&gt;12 MPa) and elongation (&gt;0.1%). Utilizing the Taguchi experimental design, the microinjection molding parameters were optimized, and they are a material temperature of 190 °C, an injection speed of 50 mm/s, and a holding pressure speed of 30 mm/s. Variance analysis identified the injection speed to be the most significant factor, contributing 50.73% to the overall effect. Immersing ACP in simulated body fluid (SBF) for six hours reduced its calcium ion concentration by 28%, with this concentration stabilizing thereafter. Biocompatibility was confirmed through an MTT assay with NIH-3T3 cells, demonstrating the PLA/PCL/ACP composite’s compatibility. Bone differentiation and mineralization tests showed the enhanced performance of both ACP and the composite material. Degradation tests indicated an initial 0.29% weight increase in the first week, followed by a 2% reduction by the fifth week. These results underscore the PLA/PCL/ACP composite’s excellent mechanical properties, biocompatibility, and suitability for injection molding, positioning it as a strong candidate for biodegradable bone screw applications.

Wind turbines’ volume and power generation capacity have increased worldwide. Consequently, their inspection, maintenance, and repair are garnering increasing attention. Structural defects are common in turbine blades, but their detection is difficult due to the relatively large size of the blades. Therefore, engineers often use nondestructive testing. This study employed an unmanned aerial vehicle (UAV) to simultaneously capture visible-light and infrared thermal images of wind power blades. Subsequently, instant neural graphic primitives and neural radiance fields were used to reconstruct the visible-light image in three dimensions (3D) and generate a 3D mesh model. Experiments determined that after converting parts of the orthographic-view images to elevation- and depression-angle images, the success rate of camera attitude calculation increased from 85.6% to 97.4%. For defect measurement, the system first filters out the perspective images that account for 6–12% of the thermal image foreground area, thereby excluding most perspective images that are difficult to analyze. Based on the thermal image data of wind power generation blades, the blade was considered to be in a normal state when the full range, average value, and standard deviation of the relative temperature grayscale value in the foreground area were within their normal ranges. Otherwise, it was classified as abnormal. A heat accumulation percentage map was established from the perspective image of the abnormal state, and defect detection was based on the occurrence of local minima. When a defect was observed in the thermal image, the previously reconstructed 3D image was switched to the corresponding viewing angle to confirm the actual location of the defect on the blade. Thus, the proposed 3D image reconstruction process and thermal image quality analysis method are effective for the long-term monitoring of wind turbine blade quality.

Various warm forming processes for AA 7075 alloy sheets integrate pre-aging, optimized process parameters, and paint bake treatment to enhance formability while minimizing strength loss. Previous studies link these improvements to matrix precipitates (MPts) characteristics, but mainly focus on post-formed strength rather than formability under warm conditions. This study evaluates the formability of AA 7075 sheets subjected to peak aging, pre-aging, and W-temper using isothermal warm tensile and limit dome height tests. Microstructural features before forming were analysed via transmission electron microscopy and small-angle X-ray scattering. The correlation between microstructural characteristics and formability was then investigated. Results indicate that the product of MPts volume fraction and average radius (fvRavg) has a greater effect on formability than MPts spacing (Sp) in conditions with significant strength differences. This is attributed to the dominant influence of deformation resistance over dynamic recovery, especially when MPts are shearable.