Multi-innovation auto-constructed least squares identification for 4 DOF ship manoeuvring modelling with full-scale trial data

This research is concerned with the problem of 4 degrees of freedom (DOF) ship manoeuvring identification modelling with the full-scale trial data. To avoid the multi-innovation matrix inversion in the conventional multi-innovation least squares (MILS) algorithm, a new transformed multi-innovation least squares (TMILS) algorithm is first developed by virtue of the coupling identification concept. And much effort is made to guarantee the uniformly ultimate convergence. Furthermore, the auto-constructed TMILS scheme is derived for the ship manoeuvring motion identification by combination with a statistic index. Comparing with the existing results, the proposed scheme has the significant computational advantage and is able to estimate the model structure. The illustrative examples demonstrate the effectiveness of the proposed algorithm, especially including the identification application with full-scale trial data.     

Ni,Cr, and Fe surfaces corroded by molten ZnCl2

Understanding the corrosion of molten ZnCl₂ on metal surfaces is significant for the corrosion protection of metals, sustainable use of molten salts, preparation of ZnO coatings, and so on. In this paper, surfaces of pure Ni, Cr, and Fe corroded by molten ZnCl₂ were investigated. The results show that Ni suffered very slight corrosion, while Cr experienced more serious corrosion than Ni, but lighter corrosion than Fe. The morphology of the corrosion of Cr and Fe, respectively, presented pitting and intergranular corrosion characteristics. Furthermore, nanostructured ZnO coatings were obtained on the surfaces of Ni and Fe, but not on the surface of Cr. The ZnO coating on the Ni surface was doped with a small amount of Zn₅(OH)₈Cl₂, and the ZnO coating on the Fe surface was doped with ZnFe₂O₄ and Zn₂OCl₂. The coatings on the Ni and Fe surfaces had an average thickness of 1.5 and 50 μm, respectively.     

地聚合物混凝土配比及力学性能研究

混凝土是巷道支护过程中的重要建筑材料,然而混凝土在巷道施工中常常出现质量问题,为了不影响正常生产,需要对其进行修补。地聚合物混凝土凝结时间快,早期强度高,界面结合能力强,耐高温性和抗冻性强,耐腐蚀性良好,具有用作修补材料的潜力。以粉煤灰和矿粉为原料,Na₂SiO₃溶液和NaOH为碱激发剂制备地聚合物胶砂,研究不同的碱激发剂模数（1.0、1.2、1.4）和掺量（10%、15%、20%）对不同龄期胶砂力学性能的影响。结果表明：当碱激发剂模数为1.2,碱掺量为15%时,胶砂强度达到最大值。设计正交试验,研究了不同水胶比（0.45、0.50、0.55）、粉煤灰掺量（30%、50%、70%）和砂率（30%、35%、40%）对不同龄期地聚合物混凝土的工作性能和力学性能的影响。结果表明：粉煤灰掺量对抗压强度影响最为显著,水胶比次之,而砂率对强度发展几乎没有影响。最优的配合比为水胶比为0.50,粉煤灰掺量为50%,砂率为35%。     

Stability-based preference selection in affinity propagation

Recently, as one of the most popular exemplar-based clustering algorithms, affinity propagation has attracted a great amount of attention in various fields. The advantages of affinity propagation include the efficiency, insensitivity to cluster initialization and capability of finding clusters with less error. However, one shortcoming of the affinity propagation algorithm is that, the clustering results generated by affinity propagation strongly depend on the selection of exemplar preferences, which is a challenging model selection task. To tackle this problem, this paper investigates the clustering stability of affinity propagation for automatically selecting appropriate exemplar preferences. The basic idea is to define a novel stability measure for affinity propagation, based on which we can select exemplar preferences that generate the most stable clustering results. Consequently, the proposed approach is termed stability-based affinity propagation (SAP). Experimental results conducted on extensive real-world datasets have validated the effectiveness of the proposed SAP algorithm.     

滩地刚性植物消浪作用特性研究

滩地植物有利于保障沿海地区的水安全,量化成熟期植物消浪作用是提升生态海岸韧性的基础。本文基于一般试验规律和两种波高消减模型,分析提出了新的滩地植物消浪系数计算方法,结合波高条件可计算林带消浪后波高,相关表达式由大量试验数据进行了验证,最后对比了由本文方法与规范方法计算的林带后波高。结果表明,阻尼因数及消浪系数能直观体现植物消浪作用特性,波浪传播方向上植物面积占横截面比例是影响植物消浪机理的关键无量纲参数。植物非淹没时,本文方法得到的林带后波高与规范方法接近;植物淹没时,本文方法能更准确描述植物消浪作用。相较于规范方法,本文方法考虑了植物淹没情况,直观揭示了林带密度、宽度、高度,植物平均直径,水深等参数的影响,适用于更多工况。基于植物消浪作用的模型可快速研判相关参数变化对植物消浪效果的影响,为生态海堤滩地刚性植物规划设计及数模研究提供科学和技术支撑。     

Mangrove forests as a nature-based solution for coastal flood protection: Biophysical and ecological considerations

Nature-based coastal protection is increasingly recognised as a potentially sustainable and cost-effective solution to reduce coastal flood risk. It uses coastal ecosystems such as mangrove forests to create resilient designs for coastal flood protection. However, to use mangroves effectively as a nature-based measure for flood risk reduction, we must understand the biophysical processes that govern risk reduction capacity through mangrove ecosystem size and structure. In this perspective, we evaluate the current state of knowledge on local physical drivers and ecological processes that determine mangrove functioning as part of a nature-based flood defence. We show that the forest properties that comprise coastal flood protection are well-known, but models cannot yet pinpoint how spatial heterogeneity of the forest structure affects the capacity for wave or surge attenuation. Overall, there is relatively good understanding of the ecological processes that drive forest structure and size, but there is a lack of knowledge on how daily bed-level dynamics link to long-term biogeomorphic forest dynamics, and on the role of combined stressors influencing forest retreat. Integrating simulation models of forest structure under changing physical (e.g. due to sea-level change) and ecological drivers with hydrodynamic attenuation models will allow for better projections of long-term natural coastal protection.     

Polyether-b-Amide Based Solid Electrolytes with Well-Adhered Interface and Fast Kinetics for Ultralow Temperature Solid-State Lithium Metal Batteries

Solid-state lithium metal batteries (SSLMBs) are highly desirable for energy storage because of the urgent need for higher energy density and safer batteries. However, it remains a critical challenge for stable cycling of SSLMBs at low temperature. Here, a highly viscoelastic polyether-b-amide (PEO-b-PA) based composite solid-state electrolyte is proposed through a one-pot melt processing without solvent to address this key process. By adjusting the molar ratio of PEO-b-PA to lithium bis(trifluoromethanesulphonyl)imide (ethylene oxide:Li = 6:1) and adding 20 wt.% succinonitrile, fast Li⁺ transport channel is conducted within the homogeneous polymer electrolyte, which enables its application at ultra-low temperature (−20 to 25 °C). The composite solid-state electrolyte utilizes dynamic hydrogen-bonding domains and ion-conducting domains to achieve a low interfacial charge transfer resistance (<600 Ω) at −20 °C and high ionic conductivity (25 °C, 3.7 × 10⁻⁴ S cm⁻¹). As a result, the LiFePO₄|Li battery based on composite electrolyte exhibits outstanding electrochemical performance with 81.5% capacity retention after 1200 cycles at −20 °C and high discharge specific capacities of 141.1 mAh g⁻¹ with high loading (16.1 mg cm⁻²) at 25 °C. Moreover, the solid-state SNCM811|Li cell achieves excellent safety performance under nail penetration test, showing great promise for practical application.     

Self-Standing Covalent Organic Framework Membranes for H2/CO2 Separation

Covalent organic frameworks (COFs) are proposed as promising candidates for engineering advanced molecular sieving membranes due to their precise pore sizes, modifiable pore environment, and superior stability. However, COFs are insoluble in common solvents and do not melt at high temperatures, which presents a great challenge for the fabrication of COF-based membranes (COFMs). Herein, for the first time, a new synthetic strategy is reported to prepare continuous and intact self-standing COFMs, including 2D N-COF membrane and 3D COF-300 membrane. Both COFMs show excellent selectivity of H₂/CO₂ mixed gas (13.8 for N-COF membrane and 11 for COF-300 membrane), and especially ultrahigh H₂ permeance (4319 GPU for N-COF membrane and 5160 GPU for COF-300 membrane), which is superior to those of COFMs reported so far. It should be noted that the overall separation performance of self-standing COFMs exceeds the Robeson upper bound. Furthermore, a theoretical study based on Grand Canonical Monte Carlo (GCMC) simulation is performed to explain the excellent separation of H₂/CO₂ through COFMs. Thus, this facile preparation method will provide a broad prospect for the development of self-standing COFMs with highly efficient H₂ purification.     

Crystallographic analysis on small fatigue crack propagation behaviour of a nickel-based single crystal superalloy

In situ observations by scanning electron microscopy show that small fatigue cracks in a nickel-based single crystal superalloy are inclined to the loading direction and propagate in dominant crystallographic manners. In order to evaluate the driving forces for inclined crack propagation, three-dimensional anisotropic linear elastic finite-element analysis is conducted. The plastic zone size on the dominant slip plane has been calculated and proposed to correlate the fatigue crack growth. It is shown that this parameter takes into account both material anisotropy and octahedral fracture modes, and it can effectively characterize small crack propagation behaviour.     

Corrosion kinetics and patina evolution of galvanized steel in a simulated coastal-industrial atmosphere

The corrosion kinetics and patina (corrosion products) layer evolution of galvanized steel submitted to wet/dry cyclic corrosion test in a simulated coastal-industrial atmosphere was investigated. The results show that zinc coating has a greater corrosion rate during the initial period and a lower corrosion rate during the subsequent period, and the patina composition and structure can greatly affect the corrosion kinetics evolution of zinc coating. Moreover, Zn₅(OH)₆(CO₃)₂ and Zn₄(OH)₆SO₄ are identified as the main stable composition and exhibit an increasing relative amount; while Zn₁₂(OH)₁₅Cl₃(SO₄)₃ cannot stably exist and diminish in the patina layer as the corrosion develops.