In marine engineering systems, water-based lubrication is considered an ideal choice for bearings in ship propulsion systems because of its environmental compatibility and operational safety. However, the low viscosity of water increases the risk of lubrication failure under boundary and mixed lubrication regimes, thereby limiting its broader applications. This study proposes a novel polyether ether ketone (PEEK)-based composite (MWCNTs/BN/Gr/PEEK with embedded perfluoropolyether oil) for water-lubricated bearings and introduces a strategy for delivering trace amounts of a secondary lubricant (PFPE) to the water-lubricated interface. Unlike conventional external oil-supply approaches, this study employs multi-walled carbon nanotubes (MWCNTs) as “reservoirs” and embeds trace lubricant within the PEEK matrix through a hot-press sintering process. This approach transforms the lubrication mechanism from an external secondary supply to an internally self-replenishing system. During friction, the synergistic interaction between the lubricant film and the water film enhances tribological performance. This functional complementarity enhances antifriction and antiwear performance. Tribological tests reveal a coefficient of friction as low as 0.013, representing an approximately 97% reduction compared with pure PEEK. This approach significantly reduces friction while maintaining operational stability and environmental compatibility, demonstrating strong potential for applications in water-lubricated bearings.

Intelligent materials with tunable properties have emerged as an important research direction in fields such as biomimetics, tribology, and shape memory. In the field of tribology, polymer materials with adjustable tribological properties can dynamically regulate their frictional behavior in response to external stimuli, enabling adaptation to different operating conditions and meeting the requirements of diverse application scenarios. However, current related studies are mainly focused on coating or complex structure constructed using advanced manufacturing techniques. In this study, an NIR-responsive shape memory cyanate ester composite was fabricated using reduced graphene oxide. Owing to the synergistic effects of photothermally induced lubricant activation and thermal softening of asperities, both the coefficient of friction (COF) and the wear rate exhibit a decreasing-increasing trend with increasing NIR power. Notably, under a specific irradiation power, the composite shows a COF reduction of up to 62%, while the wear rate decreases by more than one order of magnitude, enabling an intelligent transition from a "high-friction" state to a "self-lubricating" state. Cyclic tests further confirm that the COF of the material exhibits excellent response sensitivity and reversibility under NIR regulation. This intelligent composite, owing to its excellent photo-regulation sensitivity, holds great potential for applications in intelligent lubrication of deployable space structures, and precision transmission systems. Moreover, it provides new insights for the development of smart friction and lubrication materials.

To investigate the kinetic impact effects on small asteroids and the corresponding close-range observation requirements, we performed SPH simulations of a 600-kg aluminum projectile impacting a 35-meter basalt asteroid at 1km/s. Our analysis covered observation resolution, instrument positioning, and detectable radiation signatures. Results show that high-strength monolithic asteroids primarily experience cratering, while low-cohesion monolithic and rubble-pile asteroids are prone to fragmentation. A size-mass distribution method was developed to effectively predict the distribution of sub-resolution ejecta. For observer safety, safe positions during cratering lie within a cone above the impact plane, whereas fragmentation scenarios require dynamic avoidance trajectories for cameras based on ejecta mass flux. The study also confirmed that the impactor's vaporization spectrum is elusive due to rapid cooling; visible post-impact spectra are dominated by sunlight reflected from abundant cool, slow ejecta, with minor contributions from incandescent fast-moving ejecta. The integrated numerical and observational analysis methodology developed here provides critical data support for predicting impact outcomes and designing observation strategies in kinetic impact missions.

Intrinsic self-healing materials are crucial for preventing unexpected shutdowns and extending service life. However, such materials often fail to simultaneously achieve high strength, high-temperature resistance, and creep resistance, which severely limits their practical applications. Therefore, developing intrinsic self-healing materials that combine high strength and creep resistance remains a significant challenge. Inspired by the “pulley” mechanism, we introduce a “dual-dynamic nanobridge” structure containing dynamic imine and boroxine bonds into a “pulley-like” polyimide network to enhance the network load-bearing capacity, thereby breaking the trade-off among high strength, creep resistance, and self-healing performance. The resulting TBPI-AFGO1 polymer exhibits excellent thermal stability (Td5% = 349 °C), a high mechanical strength of 103.9 ± 1.11 MPa, the residual strain is only 0.72% after creep recovery at 180 °C. At the same time, after the damage to TBPI-AFGO1 was healed, the mechanical strength of TBPI-AFGO1 recovered to 93.32% of its original value, and the elongation at break recovered to 80.42% of its original value, demonstrating good self-healing capability. Furthermore, integrating TBPI-AFGO1 into carbon fiber fabric endows the fabric with self-healing and recyclability, significantly extending the service life of carbon fiber composites.

Polyimides (PIs) are used in cutting-edge engineering fields due to their high mechanical strength, excellent electrical insulation, and low friction coefficient, attributed to their rigid benzene ring structures. However, under prolonged service in harsh environments, PI components are prone to mechanical damage, which substantially increases the risk of operational failure and maintenance costs. Thus, developing self-healing PI materials has become crucial for enhancing operational reliability and extending service life. Nevertheless, achieving a material that simultaneously exhibits high mechanical strength, high healing efficiency, and rapid healing capability remains a formidable challenge. In this work, the formylphenylboronic acid is introduced as a single monomer to concurrently incorporate dynamic imine bonds (-C=N-) and reversible boroxine structures (-B3O3-) into the PI backbone, achieving a "two birds with one stone" molecular design. This strategy endows the resultant PI with excellent mechanical properties (a tensile strength of 87.03 MPa and a break elongation of 21.41%) and a breakthrough self-healing property, enabling repair efficiency of 99.92% and damage repair in just 30 s. Notably, it resolves the critical bottleneck in the field-the typical trade-off between strength/toughness and rapid/healing efficiency-with the achieved efficiency and speed being the highest values reported to date. Furthermore, inspired by the perspiration and healing mechanisms of human skin, a heterogeneous bilayer architecture is constructed to further enhance the healing material's resistance to extreme mechanical damage such as severe abrasion under heavy-load conditions. This work not only opens up a new avenue for designing integrated materials that combine high strength, thermal stability, and ultrafast self-healing capacity, but also provides a practical strategy for prolonging the service life of PIs in extreme environments while mitigating risks associated with unexpected mechanical failures.

Kinetic impact is regarded as the most technically feasible method for asteroid defense.Conducting an on-orbit demonstration and verification mission would not only enhance the technological maturity of kinetic-impact deflection,but also reveal the orbital deflection behavior of near-Earth asteroids,thereby providing decision-making support for future responses to real near-Earth asteroid impact threats.The orbital dynamical characteristics and structural,physical,and chemical properties of near-Earth asteroids are critical to the successful implementation of kinetic-impact missions.At the same time,such missions would provide an unprecedented opportunity to investigate the internal structure,composition,and mechanical properties of near-Earth asteroids.In addition,kinetic impact would serve as a unique"natural experiment,"offering a key case study for impact physics from the perspective of comparative planetology and thereby promoting the coordinated development of planetary science and planetary defense technologies.Focusing on China's first asteroid defense demonstration and verification mission planned before 2030,this paper systematically reviews the frontier scientific questions in kinetic-impact asteroid defense,with the aim of providing a reference for mission design,implementation,and preliminary scientific research.

Lubrication systems that can autonomously adapt to dynamic operating conditions remain a longstanding challenge in tribological materials. Here, we report hierarchical hollow MoS2 microspheres that function as both solid lubricants and micron-scale reservoirs for lubricating oil, enabling adaptive solid–liquid synergistic lubrication. The hollow MoS2 architecture was synthesized via a hydrothermal route and impregnated with polyalphaolefin (PAO10) to produce PAO10@MoS2 microcapsules (MMCs) with an oil loading of 54.7 wt%. Incorporation of 10 wt% MMCs into epoxy reduced the friction coefficient to 0.059 and the wear rate to 6.55 × 10−8 mm3/(N·m). The superior tribological performance originates from the synergistic lubrication mechanism, in which layered MoS2 provides continuous solid lubrication while encapsulated PAO10 is released in situ during sliding to replenish the lubricating interface. Beyond passive lubrication, the composite exhibits rapid, reversible, and on-demand regulation of friction under near-infrared (NIR) irradiation owing to the excellent photothermal conversion capability of MoS2. NIR illumination immediately decreases the friction coefficient, whereas the initial friction state is fully restored after the light is removed, demonstrating dynamically switchable tribological behavior. These findings establish a versatile strategy for integrating lubricant storage, controlled release, and photothermal regulation into a single material platform, providing a pathway toward intelligent tribological systems with actively tunable frictional performance.

This paper presents the design and implementation of a high-density, deterministic trigger distribution system tailored for the C-band photocathode electron gun test platform at the Southern Advanced Photon Source (SAPS). Implemented within a scalable 6U VME modular architecture, the system achieves high-density integration by consolidating a master controller, clock distribution network, and 80 heterogeneous output channels into a single chassis. This design leverages a high-performance FPGA core combined with custom backplane interconnections to establish a master-slave topology, significantly reducing the system footprint compared to stacked standalone generators. To guarantee timing determinism in high-noise environments, precise placement and timing constraints are applied to the FPGA logic, while optical isolation is employed to mitigate electromagnetic interference. Furthermore, a dual-channel SFP optical signaling architecture enables seamless expansion to 160 synchronized channels. A remote control framework based on a serial server and a virtual machine Input/Output Controller (IOC) facilitates flexible configuration. Performance tests demonstrate adjustable trigger frequencies from 1 Hz to 100 Hz, with delays and pulse widths tunable from 0 to 10 ms at a resolution of 10 ns (or the RF period). The local electrical output exhibits an ultra-low RMS jitter of 6.55 ps (60 ps peak-to-peak). For remote optical distribution, the system maintains a sub-nanosecond RMS jitter of 119.5 ps, with peak-to-peak variation confined to 1 ns due to the combined effects of transceiver optoelectronic conversion (utilizing HFBR-1414T/2412T modules) and fiber transmission. The system has been successfully commissioned and is currently in reliable routine operation, verifying the architecture as a robust, highly integrated, and cost-effective solution for compact accelerator facilities.

Efficient and accurate querying of Process Variables (PVs), core parameters in the EPICS control system used in particle accelerators like the China Spallation Neutron Source (CSNS), is vital for real-time monitoring, rapid fault diagnosis, and precise experiment tuning. PVs often include Chinese meanings and descriptions alongside English strings. Traditional query methods struggle with the volume, diversity, and ambiguity of PV information due to incomplete user memory, synonym usage, spelling errors, and the inability to identify semantically similar PVs, impacting efficiency and accuracy. This paper proposes a PV query algorithm based on a multi-way recall weighted mechanism to address these challenges. The algorithm integrates deep semantic understanding recall using semantic similarity based on advanced word embedding models, efficient text feature recall employing keyword matching based on the BM25 algorithm, and intelligent fusion and optimized re-ranking of multi-way recall results through a dynamic weighting mechanism. A dynamic truncation strategy, adaptively filtering results based on the similarity score gradient, further optimizes query result quality and reduces redundancy. Experimental results demonstrate that the proposed method maintains low query latency while improving both recall rate and F1-score compared to single recall models. These results validate the algorithm’s effectiveness in significantly optimizing the efficiency and accuracy of PV data retrieval in particle accelerator environments, providing strong technical support for the intelligent operation and maintenance of large scientific facilities.

The 2029 close encounter of near-Earth asteroid (99942) Apophis, at approximately 38,000 km from Earth center, offers a unique opportunity to advance planetary science, defense, and public engagement. This rare event enables real-time observations of tidal effects, surface displacement, spin changes, and dust ejection, deepening our understanding of rubble-pile asteroids and improving models of their evolution. Detailed data will refine predictions of the Yarkovsky and YORP effects, enhancing asteroid dynamics research. From a planetary defense perspective, Apophis provides a critical test case for impact risk assessment and mitigation strategies, informing rapid-response reconnaissance missions. Public outreach during the event will raise awareness of asteroid science and planetary safety, fostering interest in space exploration. International collaborations, including NASA’s OSIRIS-APEX and ESA’s RAMSES missions, along with the potential contributions from China, aim to maximize scientific returns, making the 2029 Apophis flyby a milestone in global planetary exploration and defense efforts.

The Gravity Tractor (GT) is a spacecraft that deflects an asteroid using its gravitational force to gradually alter the asteroid’s trajectory without making physical contact. This paper proposes a comprehensive mission optimization framework to maximize orbital deflection distance in variable-mass GT missions, incorporating key constraints: launch performance, warning time, and operational strategies. Simulation results suggest that the deflection distance of GT does not increase linearly with warning time due to launch window constraints, and the three-pulse transfer scenario does not provide significantly greater deflection distance compared to the two-pulse transfer scenario. Moreover, in the static hovering scenario, the deflection distance first increases and then decreases with the effective tractor distance, whereas in the displaced orbit scenario, it decreases monotonically. Finally, considering the launch performance of CZ-5, a 10-year warning time enables the defense against 50-meter asteroids, while a 20-year warning time enables the defense against 100-meter asteroids. This research provides valuable insights into the evaluation of GT deflection efficiency and the engineering design of GT-based missions.

Nucleotide bases encode genetic information through specific structural arrangements. Their abnormalities in structure and composition, such as gene mutations and epigenetic modifications, can trigger multiple diseases. Precise discrimination of bases is critical yet challenging due to their high structural similarity. Herein, we report triphenylamine-based covalent organic framework nanosheets (TPA CONs) as a fluorescent biosensor for nucleobase discrimination and deoxyribonucleic acid (DNA) methylation quantitative profiling, driven by electrostatic potential-mediated base selectivity. Combined experimental and computational studies reveal that the electrostatic potentials of four bases govern their affinity to the negatively charged CONs following an order of thymine (T) > guanine (G) > adenine (A) > cytosine (C). Consequently, T-rich sequences interact strongly with CONs and trigger efficient fluorescence quenching via photoinduced electron transfer, while C-rich sequences restore fluorescence. Leveraging this property, we detected human estrogen receptor α (ERα) gene regional methylation in cultured breast cancer cells with a limit of detection of 2.4% and further extended the platform to human hepatocellular carcinoma (HCC) specimens for eyes absent homologue 2 (EYA2) gene methylation analysis, yielding results highly consistent with gold standard pyrosequencing. This work is the first to exploit COF for direct nucleobase discrimination and quantitative DNA methylation analysis, elucidating the COF-nucleobase interaction mechanism and highlighting their potential for epigenetic detection.

Polyimide (PI), a special engineering plastic, features robust mechanical properties and exceptional thermal stability. However, its processing and molding are limited by thermal pressing, making the fabrication of high performance customized complex 3D shapes a significant challenge. Here, we present a PI combines high performance with the ability to access 3D printing and recyclability, facilitated by a snap-hook polyimide (SHPI) strategy based on dynamic boroxine network. Capping the liner PI with phenylboronic acid, which could reversible formation of six-membered boroxine rings occurs at both ends of the liner PI under heat and specific solvents, resulting in dynamic crosslinked PI (DCPI) and liner SHPI. Due to the stability and high bond energy of the boroxine, DCPI exhibits exceptional mechanical properties (tensile strength ti 110 MPa, Young's modulus ti 3 GPa) and thermal performance (Tg ti 223 degrees C, Td ti 539 degrees C). The selective cleavage of boroxine bonds enables the snap-hook functionality that allows reversible conversion between DCPI and SHPI, imparting solubility and facilitating infinite recyclability, 3D printability, and sustainable printability, thereby achieving the creation and elimination of high-performance PI 3D structures. Moreover, the 3D-printed PI sealing ring structure, as a demonstration, showcases its limitless potential for applications in the aerospace industry. This work opens new avenues for the personalized construction of high-performance engineering polymers and provides a viable approach for the development of sustainable 3D printing.

Developing polyurethane that can withstand ultra-low temperatures is key to expanding its applications in low- temperature environments. Spider silk demonstrates high toughness in low-temperature environments due to its hierarchical hydrogen bonds network. Inspired by spider silk, a polyurethane elastomer (SPU-DTPx) with exceptional strength, superior toughness, low-temperature resistance, and recyclability were synthesized. The dense hydrogen bonds in the urethane bonds lead to curled and entangled molecular chains at low temperature. SPU-DTP0.8 achieves a maximum tensile strength of 86.71 MPa, maximum elongation at break reaching 226.93 % at-90 degrees C, with toughness of SPU-DTP0.8 of 109.98 MJ m- 3 , only 37.27 % lower than that at 20 degrees C. Utilizing hydrogen bonds and molecular chain migration, SPU-DTP0.8 demonstrates excellent recyclability, maintaining key mechanical properties after reprocessing. This elastomer could endure extreme supercold temperatures and offer considerable promise for creating elastic devices, flexible spacecraft, and soft robots designed for use in extremely low-temperature environments like outer space or polar areas.

To enhance the mechanical properties of polyurethane elastomers, various strategies have been developed, including the incorporation of multiple hydrogen bonds, mechanical interlocking, and supramolecular interactions. However, achieving an optimal balance between strength and toughness while maintaining high tensile properties at both room and cryogenic temperatures remains a significant challenge. In this study, we synthesized a poly(boron-urethane) with ultra-high performance by introducing aromatic side chains into the polyurethane matrix. The resulting poly(boron-urethane) demonstrates remarkable mechanical properties, with tensile strength (70.1 +/- 4.4 MPa) and fracture toughness (437.5 +/- 61.1 MJ/m3). These exceptional mechanical properties were attributed to the synergistic effects of pi-pi stacking interactions and hierarchical hydrogen bonding. This synergy not only serves as reversible cross-linking points and sacrificial bonds that facilitate substantial energy dissipation, but also forms nanostructured domains that act as nanofillers, thereby enhancing the mechanical properties. Furthermore, the incorporation of bulky aromatic rings of the chain extenders mitigate the crystallization tendency of PTMEG, resulting in improved low-temperature flexibility. This chemcial modification contributes to significant tensile strength (100.6 MPa) and fracture toughness (237.5 MJ/m3) at -40 degrees C, along with excellent solvent resistance. Overall, the combination of pi-pi stacking and hierarchical hydrogen bonding, synergistically enhances the entropic elasticity of the elastomer network, effectively balancing the strength and toughness of the material across varying temperatures, making it well-suited for extremely cold environments.

Machine learning, as an advanced technology, has achieved remarkable success across various fields due to its powerful data processing and pattern recognition capabilities. When applied to particle accelerators, it has the potential to optimize performance, enhance operational efficiency, and drive innovation in accelerator technology. However, the adoption of machine learning often necessitates extensive knowledge of algorithms and programming, which can be time-consuming and create barriers to accessibility. To overcome these challenges, the development of the machine learning as a service for accelerators (MLaaS4ACC) system is proposed. This system is designed to simplify the use of machine learning tools for accelerator researchers, efficiently perform machine learning tasks, and continuously expand and optimize functionalities tailored to the unique requirements of accelerator systems. Currently, MLaaS4ACC can effectively perform several straightforward machine learning tasks. Compared to traditional methods, it reduces the time required for actual tasks and simplifies the model training process, while yielding results that are not significantly different. The model already meets the necessary requirements. Looking ahead, it is essential to enhance and expand the system in various aspects to address more complex demands. Improvements in both the performance and functionality of MLaaS4ACC are necessary to ensure it meets these evolving requirements.

Implementing the flyby to Near-Earth Asteroids (NEAs) with the potential impact risks to the Earth allows for obtaining detailed physical parameters, thereby supporting the high-precision orbit prediction and planetary defense strategy. Different from those conducted asteroid flyby missions, in the 12th China Trajectory Optimization Competition (CTOC-12), a NEAs flyby trajectory design problem using reusable probes that depart from a Lunar Distant Retrograde Orbit (DRO) station in the cislunar space was released. The objective was flyby to as many NEAs as possible using up to 20 probes within a total of 10 years. The ∑ team proposed a solution that can explore 47 NEAs using 11 probes, ranking the first in the competition. In this paper, the methods and results from the winning team are introduced, including mission analysis and preliminary design, and low-energy transfer trajectory optimization. In particular, a round-trip trajectory is divided into three phases: deep space transfer, indirect transfer between the Earth to DRO, and DRO phasing and rendezvous. With the combination of global optimization and local optimization algorithms, the required velocity increments to change the orbital planes are effectively reduced, thus increasing the number of the explored NEAs. The final solution of our team is presented and the results are compared with those of the top three teams. The competition demonstrates that the regularization of flyby missions from the cislunar space to explore NEAs with the potential impact risks to the Earth is the feasible and promising.

Achieving 4D printing of shape memory polymers with both high strength and high transition temperature remains challenging due to the inherent incompatibility between the rigid molecular structure required for high strength and the molecular structure that moves on demand necessary for the shape memory effect, the limitations of high-performance polymer reaction kinetics, as well as internal stress during the printing process. Here, a direct ink writing (DIW) printed high-precision cyanate ester-urethane (CU) shape memory polymer with excellent performance was accomplished by incorporating two dynamic covalent bonds (carbamate and cyanuric acid) through copolymerizing cyanate ester with polyurethane acrylates. During curing, carbamate and cyanuric acid enable stress relaxation and polymer network rearrangement, facilitating the permanent reconfiguration of CU to form a novel triazine network structure. As a result, a high mechanical properties CU with excellent strength (83 MPa) and superior Young's modulus (2.37 GPa) were obtained, besides, the transition temperature (near 250 degrees C) is the highest in comparison to currently reported 4D-printed shape memory polymers. Furthermore, this reconfigurability was demonstrated by imprinting various surface patterns at microscopic level. Moreover, the reconfigurability of CU provides a novel strategy for smart molds in deformation and easy demolding. Overall, this study opens up a new avenue for the development of high-performance 4D printed shape memory polymers. (c) 2024 Kingfa Scientific and Technological Co. Ltd. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

To improve the modulus and tensile strength of polyimide films, this study utilized diamines with amide bonds as monomers, introducing hydrogen bonding into the material. Additionally, a microbranched cross-linked structure was created by incorporating a triamino compound, and its effect on film properties was analyzed. The results showed that the microbranched cross-linked structure and amide bonding significantly improved the storage modulus, tensile strength, shape memory properties, and toughness of the polyimide films. Specifically, at 2% concentration of 1,3,5-tris(4-aminophenoxy)benzene, the storage modulus of the polyimide films reached 12.97GPa, the tensile strength was 243 MPa, the elongation at break was 5.58%, and the toughness was improved by 2.59 times. At this concentration, the shape fixation rate of normal polyimide was 96.7%, and the shape recovery rate was 92%. These findings suggest that the modified polyimide films exhibit high strength and are suitable for applications in high-temperature environments.

Responsive materials have significant application value because of their ability to actively adjust their structure or properties in response to external stimuli. Poly(N-isopropylacrylamide) (PNIPAM) is widely used to form micelles, particularly for drug delivery, because its lower critical solution temperature (LCST) is close to body temperature. However, the preparation of micelles based on PNIPAM block copolymers often involves complex processes, which limit their broader application. Here, we employed polymerization-induced self-assembly (PISA) combined with in situ crosslinking to synthesize stabilized thermoresponsive micelles, such as poly(glycerol methacrylate)-b-poly(N-isopropylacrylamide)-B (PGMAx-b-PNIPAMy-B), which are spherical micelles with a thermoresponsive core of PNIPAM and a crosslinked shell of PGMA formed by sodium tetraborate decahydrate. The micelles exhibited rapid and reversible self-assembly and collapsed at 31 degrees C, enabling temperature regulation through light transmittance, which makes them suitable for smart window applications. Furthermore, these micelles demonstrated excellent friction-reducing and wear-resistant properties at various temperatures (25-36 degrees C) and under various loads (20-70 N), indicating their adaptive lubrication as additives. This work presents the facile fabrication of thermoresponsive micelles and expands the application of PISA technology in the tribological field.