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To investigate the effects of exogenous γ-aminobutyric acid (GABA) application on the growth, development, and related parameters associated with different physiological and biochemical processes of Isatis indigotica Fortune ( I. indigotica ) seedlings, a pot experiment was conducted. Seedlings were collected from two provenance areas (Gansu and Hebei) and treated at the six-leaf stage with four GABA concentrations: 0 (CK), 2.5 (T1), 5 (T2), and 7.5 (T3) mM·L -1 . Compared with CK, T1 and T2 treatments improved plant height, total fresh mass, and total dry mass at all sampling stages, with increments of 0.99%-7.86%, 2.99%-12.79%, and 1.27%-6.90%, respectively. These promotional effects were attributed to increased photosynthetic capacity, pigment contents, and activities of nitrogen metabolism enzymes. Meanwhile, root morphology was also promoted by T1 and T2 treatments. In contrast, inhibitory effects of T3 treatment on plant height, total biomass accumulation, and root morphology were also observed. Furthermore, exogenous treatments T1 and T2 markedly elevated the antioxidant capacity of I. indigotica seedlings, as evidenced by the increased activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), along with the enhanced soluble protein content in both leaves and roots. Meanwhile, these two treatments significantly reduced the accumulation of malondialdehyde (MDA) and hydrogen peroxide (H 2 O 2 ) in the aboveground and underground tissues of the seedlings. Structural equation modeling (SEM) further revealed that the total antioxidant capacity exerted positive regulatory effects on plant height, total biomass accumulation, and root morphological traits through both direct and indirect pathways. Principal component analysis (PCA) demonstrated that T2 treatment induced the most prominent variation in seedling growth and physiological traits. Specifically, glutamate synthase (GOGAT) activity showed the strongest correlation with the first principal component (PC1), while POD activity was most closely associated with the second principal component (PC2). Collectively, these findings suggest that 5 mM·L -1 is the optimal concentration of exogenous GABA for the cultivation of I. indigotica seedlings.

The foundations of many large onshore and offshore structures are designed to be symmetrical polygons (e.g. octagons). However, the available analytical approaches for the ultimate limit state design of shallow foundations under combined loadings focus predominately on strip, rectangular and circular foundations. Although equivalent inscribed circular foundations have been recommended for foundation design by some guidelines, this simple approximation for octagonal foundations needs to be rigorously assessed due to the high dependence of the failure envelope on foundation shapes. The present study has investigated the general VHM (vertical, horizontal and moment) failure envelope of octagonal foundations under a zero-tension interface for undrained soil conditions using finite element analysis. The effects of soil strength heterogeneity and foundation embedment on the VHM failure envelope have been investigated. Analytical expressions have also been proposed to characterize the failure envelopes for use in design. The results show that octagonal foundations have larger bearing capacity than the corresponding circular foundations, and the difference (around 10%) between them is not negligible. A full 3-D analytical expression for the VHM failure envelope has also been proposed based on the calculated failure envelopes.

The design of shallow foundations for wind turbines is typically governed by serviceability and fatigue limit states. To estimate the deformations of shallow foundations under working loads, existing design standards generally employ analytical uncoupled isotropic elastic solutions based on idealized soil conditions. However, many natural soil deposits exhibit some degree of stiffness anisotropy due to their deposition and complex stress history. This study has investigated coupled elastic stiffness coefficients for circular shallow foundations founded on cross-anisotropic soils under combined VHMT loadings (vertical, horizontal, moment and torsional) using finite element analysis. A three-parameter anisotropic soil model was applied to the problem. The study extensively explores the effects of soil stiffness non-homogeneity (i.e. linear increase of elastic modulus with depth) and foundation embedment on the foundation stiffness coefficients. Fitted expressions of these stiffness coefficients were also derived. In addition, a practical application using the proposed stiffness coefficients was presented to demonstrate the effects of soil stiffness anisotropy on the responses of a typical large wind turbine shallow foundation.

Core–shell structure Cu@Pd/C catalysts were prepared in two steps combining microwave-assisted glycol reduction and chemical impregnation method for the first time. Compared with the traditional one-step synthesis of PdCu/C alloy catalysts by microwave (marked as M-PdCu/C) and impregnation (denoted by I-PdCu/C) method, respectively. The Cu@Pd/C catalysts were prepared in two-step show better catalytic performance toward formic acid oxidation, due to its special core–shell structure and better dispersion. On this basis, different proportions of Cux@Pdy/C (x:y = 1:1, 1:2, 1:3, 1:4 and 1:5) catalysts were synthesized by the two-step strategy. The relationship between lattice strain, electron distribution and catalytic performance were explored by physical and chemical characterization. X-ray diffraction and X-ray photoelectron spectra analyses showed that the introduction of Cu lead to the lattice contraction and modified electronic structure of Pd. The electrochemical test showed that Cu@Pd3/C sample has the highest activity toward formic acid electro-oxidation. Its mass activity is about 3.3 times that of Pd/C catalyst that was synthesized by impregnation method (labelled as I-Pd/C). At the same time, the Cu@Pd3/C catalyst also demonstrated improved stability.The low-palladium catalyst with a Pd–Cu shell–core structure was synthesized by two-step method and has excellent catalytic activity and stability for formic acid electro-oxidation.

A spacecraft deployable arm is one of the key components of spacecraft. The assembly accuracy of space deployable arms restricts the improvement of spacecraft performance. Therefore, it is important to analyze the factors influencing the assembly accuracy of deployable arms to optimize the assembly process. This paper studies the precision assembly of deployable arms, with a spacecraft deployable arm as the specific research object. In the study, the assembly process is modeled theoretically and analyzed by Finite Element Analysis. Finally, the assembly experiment of the deployable arm is carried out based on the research.

Estimation of the bearing capacity and deformations of large shallow foundations under combined loadings can be of great significance. Some geotechnical design guidelines recommend the failure load envelope method for ultimate limit state analysis. Since many investigations of this method focus primarily on undrained failure envelopes using unlimited-tension interfaces, zero-tension interfaces have not been well investigated. In addition, less work is available on drained failure envelopes. For serviceability limit states, the majority of approaches used are based on uncoupled, isotropic assumptions. Further work needs to be done on more appropriate elastic solutions for combined loadings.General VHMT failure envelopes for circular foundations under undrained and drained soil conditions have been investigated using finite element analysis. The effects of soil strength heterogeneity, foundation embedment and surficial crustal layer have been examined for undrained soil conditions. In addition, cohesive-frictional soils have been considered for drained soil conditions. In comparison, classical bearing capacity theories appear to be rather conservative for combined loadings.To estimate the deformations of large shallow foundations under combined loadings, researchers have proposed many analytical isotropic elastic solutions based on idealized soil conditions. However, many natural soils will be anisotropic or at least transversely isotropic due to their complex deposition history. This research has investigated the coupled elastic stiffnesses for circular foundations founded in cross-anisotropic soils. Gibson and embedment correction factors have been derived to account for the effects of soil stiffness non-homogeneity and foundation embedment.

PurposeThe purpose of this study is to establish an assembly accuracy analysis model of deployable arms based on Jacobian–Torsor theory to improve the assembly accuracy. Spacecraft deployable arm is one of the core components of spacecraft. Reducing the errors in assembly process is the main method to improve the assembly accuracy of spacecraft deployable arms.Design/methodology/approachFirst, the influence of composite connecting rod, root joint and arm joint on assembly accuracy in the tandem assembly process is analyzed to propose the assembly accuracy analysis model. Second, a non-tandem assembly process of “two joints fixed-composite rod installed-flange gasket compensated” is proposed and analyzed to improve the assembly accuracy of deployable arms. Finally, the feasibility of non-tandem assembly process strategy is verified by assembly experiment.FindingsThe experiential results show that the assembly errors are reduced compared with the tandem assembly process. The errors on axes x, y and z directions decreased from 14.1009 mm, 14.2424 mm and 0.8414 mm to 0.922 mm, 0.671 mm and 0.2393 mm, respectively. The errors round axes x and y directions also decreased from 0.0050° and 0.0053° to 0.00292° and 0.00251°, respectively.Originality/valueThis paper presents an assembly accuracy analysis model of deployable arms and applies the model to calculate assembly errors in tandem assembly process. In addition, a non-tandem assembly process is proposed based on the model. The experimental results show that the non-tandem assembly process can improve the assembly accuracy of deployable arms.

A new perturbation technique and finite-element method, which incorporates an undetermined-coefficients approach, is proposed to conduct stochastic simulation for problems of groundwater flow. Formulas of the mean value and variance of groundwater head are derived to exclude the process of computing the first and second-order derivatives of groundwater head with respect to stochastic variables (coefficient of transmissibility, storage coefficient, etc.) in the calculation process of common finite element methods. For ordinary stochastic groundwater problems, the statistical properties of groundwater head can be easily obtained by using the proposed method, which is especially efficient for the stochastic problems that have fewer input stochastic variables. A stochastic numerical simulation of a two-dimensional confined-groundwater flow problem has been conducted to validate effectiveness and determine the limitations of the proposed method. The results illustrate that the accuracy and efficiency of the method proposed are satisfactory, and that the computing time is shorter when there is a small number of input stochastic variables.

As museums shift their responsibilities and functions towards audience-centered approaches, research on exploring museum cultural communication strategies through visitor experiences has gained increasing attention from both academia and industry. This study focuses on the newly opened Nan Song Deshou Palace Relics Site Museum in Hangzhou, China, completed at the end of 2022, and its visitors. Data were collected through on-site surveys and in-depth interviews. The research findings indicate that the current motivations of museum visitors manifest primarily in three forms: knowledge exploration, social interaction, and psychological restoration. After evaluating the existing museum service quality based on the field of experiential value in marketing management, two main issues and features were identified. The issues include sub-optimal visitor pathways and layout, dissatisfaction with staff services, and shortcomings in promotion and communication. The overall cultural learning and interactive experience for the entire visitor base also require improvement. The features are characterized by differentiated cultural and creative consumption in the museum and the emergence of interrelated consumer demands. Based on these findings, the study provides targeted recommendations for future museum construction and communication strategies.

Highly stretchable, soft silicone elastomers are of great interest for the fabrication of stretchable, soft devices. However, there is a lack of available chemistries capable of efficiently preparing silicone elastomers with superior stretchability and softness. Here we show an easy curing reaction to prepare silicone elastomers, in which a platinum-catalyzed reaction of telechelic/multi-hydrosilane (Si–H) functional polydimethylsiloxane (PDMS) in the presence of oxygen and water leads to slow crosslinking. This curing chemistry allows versatile tailoring of elastomer properties, which exceed their intrinsic limitations. Specifically, both highly stretchable silicone elastomers (maximum strain of 2800%) and extremely soft silicone elastomers (lowest shear modulus of 1.2 kPa) are prepared by creating highly entangled elastomers and bottle-brush elastomers from commercial precursor polymers, respectively. Several strategies have been explored for overcoming limitations on the ultimate extensibility and softness of silicone elastomers but they either increase process complexity or lead to mechanical instabilities in the resulting elastomers. Here the authors report an easy curing reaction which allows versatile tailoring of elastomer properties exceeding their intrinsic limitations