Three novel ductile and single-phase BCC structurerefractory high-entropy alloys (RHEAs)Ti₄₀Nb₂₅V₁₅Mo₅Zr₁₅ ,Ti₄₀Nb₃₀V₂₀Mo₅Zr₅ andTi₄₀Nb₃₀V₂₀Mo₅Cr₅were developed, and the alloy, exhibit good strength and toughness at room temperature,the alloy Ti₄₀Nb₂₅V₁₅Mo₅Zr₁₅has a maximum tensile strength of 1 037 MPa. With the decrease of Zr content, the fracture elongation of Ti₄₀Nb₃₀V₂₀Mo₅Zr₅increases from 8.94% to 13.96%.A single layer of corrosion diffusion is only formedafter a static lead-bismuth saturated oxygen corrosion testto Ti₄₀Nb₃₀V₂₀Mo₅Cr₅at 450 ℃ for 100, 300, and 700 h.The thickness of the corrosion layer dno't change significantly with time.

The friction and wear properties of impregnated graphite were explored by TRB³ friction testing machine, and the GCr15 steel ball, Si₃N₄, and Al₂O₃ ceramic ball were used as friction pairs in the form of ball/plane contact. The friction coefficient, wear volume, wear mark contour, and surface morphology of the grinding mark were characterized and analyzed by scanning electron microscope and laser confocal microscope. The friction scratches and wear characteristics of impregnated graphite under different normal loads were explored aiming to establish an energy wear model to explore the changing mechanism of contact state during wear and predict the wear process. The results showed that with the gradual increase of hardness of the upper specimen, the friction coefficient gradually increases under low loads and decreases under high loads. Under different friction pair effects, the surface of graphite presents separately shallow surface wear marks similar to “U”-shaped, “V”-shaped, and “W”-shaped contours, respectively. The main wear mechanisms between graphite and GCr15, Si₃N₄ and Al₂O₃ pairing pairs are adhesive wear, abrasive wear, and slight oxidation wear. Material transfer, peeling, and furrow phenomena are evident between the surfaces of the friction pair.

The effects of metakaolin content on the fluidity, rheological parameters, thixotropy, and viscoelasticity of polymer-modified cement pastes with different water-to-binder ratios were studied. The results showed that the rheological properties of the fresh composite paste incorporating metakaolin conform to the H-B model during the initial mixing stage, and all the pastes show the rheological characteristics of shear thinning. With the increase of metakaolin content, the fluidity, yield stress, and plastic viscosity of the paste all increase. After adding 20% metakaolin, the thixotropic loop area of cement paste increases from its original value of 1 502 Pa·s^－1 to 6 672.63 Pa·s^－1, and lower water-to-binder ratio pastes correspond to a larger thixotropic area. All the composite pastes have obvious viscoelastic properties, and the critical strain amplitude and storage modulus values of linear viscoelastic range increase as the metakaolin content increases.

In order to improve the mechanical properties and durability of geopolymer concrete, experimental studies were conducted on the effects of incorporating polypropylene fibers of varying lengths and dosages on the mechanical properties, frost resistance, chloride ion corrosion resistance, and crack resistance of geopolymer concrete. Furthermore, based on SEM experiments, the mechanism of action of polypropylene fibers was further elucidated from a microscopic perspective. The research results indicated that the addition of polypropylene fibers can improve both the mechanical properties and durability of geopolymer concrete. Specifically, when the fiber content is 0%-0.6%, the improvement effect of geopolymer concrete becomes more pronounced with the increase of fiber content. However, when the dosage exceeds 0.6%, both the mechanical properties and durability begin to decline. SEM analysis further indicated that polypropylene fibers can improve the integrity and compactness of the matrix, thereby significantly improving the mechanical properties and durability of geopolymer concrete. Ultimately, the optimal dosage of polypropylene fibers is recommended to be 0.6% with a length of 12 mm.

The gearbox is an important component of the wind turbine generation system. However, its large volume and high weight pose significant constraints on the development of wind turbine. Taking the 1.5 MW wind turbine as the research object, a mathematical model is established for the lightweight optimization of the gear transmission system, and the genetic algorithm is used to solve the optimization. The optimization results show that the genetic algorithm is practicable and effective, with a reduction of 4.59% in the volume of the optimization gear transmission system, which consequently to the diminution of both the volume and the total mass of the gearbox system. The feasibility of the optimization results is verified by the transmission efficiency of the planetary gear transmission system. The paper provides a new approach to the lightweight design of gear transmission systems in wind turbines.

When WEDM machines non-circular gears, electrical parameters are recognized as pivotal factors affecting the tooth profile error of non-circular gears. Orthogonal experiments were designed to analyze WEDM non-circular gears by using the maximum tooth profile errors at the gear tooth root, tooth profile middle and tooth top respectively. Through variance analysis and main effect analysis methods, the influence law of WEDM electrical parameters, including peak current, pulse width, pulse interval, and tracking, on the tooth profile error of non-circular gears at the tooth root, tooth profile middle, and tooth top was studied. At the same time, regression analysis was performed on the tooth profile errors, machining duration, and process parameters to establish regression models. The multi-objective optimization of the regression models was conducted using the Grey Wolf Optimization algorithm. The results of this study obtain the optimal parameter combination for different parts of the WEDM non-circular gear tooth profile, which can provide a reference for actual processing.

In addressing the stability concerns associated with the disassembly process of wind turbine tower structures, the finite element numerical analysis method is used to analyze the static force characteristics of the tower when lifting, considering the factors of the hook position and the number of lifting lugs, so as to find a reasonable configuration scheme for tower dismantling. Firstly, focusing on the 2MW wind turbine tower, the tower dismantling scheme process is elaborately discussed. Subsequently, the finite element model of the heaviest section of the tower (the first segment) is constructed, and the finite element numerical analysis method is applied to compare and analyze the deformation-resisting ability and stress response characteristics of the first section of the tower structure with different hook positions and the number of lugs. The results show that compared with the use of two lugs for lifting, the deformation response of the tower can be greatly reduced by using 3 and 4 lugs, with maximum reduction rates of 81% and 87.3%, respectively. In addition, when the ratio of the hook distance from the tower top axis to the height of the first section of the tower is greater than 0.6, using three lugs contributes more to reducing the overall deformation of the first tower segment compared to using four lugs. At the same time, the equivalent stress of the first section of the tower with three lugs is smaller than that with two and four lugs throughout the disassembly process, with the smallest variation in equivalent stress amplitude observed. This shows that the first section of the tower is most stable when using three lugs, and the results of the study can provide a solid scientific basis for the requirements of the relevant standards or technical specifications.

Aiming at the impact of the coking product on the inner wall of the parabolic trough receiver on the heat transfer of the heat conduction oil and the safety of the receiver, the apparent morphology and characteristics of the coking product in the receiver of a trough solar thermal system after three years of operation were studied. The results show that the coking product presents a thick, pit-like rough surface in the circumferential direction of the metal tube, and a thin non-uniform distribution on the non-focusing side. Additionally, the particles of coking products display distinct three-dimensional characteristics, appearing as two forms of coking agglomeration focusing and dispersed coking. The true density of coking products after stacking is 1.259 7 g/cm³, and their specific heat capacity ranged from 0.83 to 2.11 J/(g·K) as measured by the Differential Scanning Calorimetry (DSC) Sapphire method. Furthermore, the thermal conductivity of bulk metal tube samples with coking products is 24.05 W/(m·K), measured using the flash method at 400 ℃, indicating a 21.7% decrease compared to non-coking metal tubes. The coking product significantly affected the heat transfer performance of the metal tube for the parabolic trough receiver.

In order to study the phase difference between the circumferential polygons of wheels on the same axle, a coupled rigid-flexible vehicle-track dynamic model based on wheelset flexibility was established. The effects of phase difference variation on the wheel-rail dynamic response are analyzed under different operating speeds when wheels on the same axle exhibit polygons of the same order. Furthermore, its influence on the evolution of wheel wear behavior is explored. The results show that when there is a phase difference in the third-order wheel polygon, the vertical impact between the wheel and rail decreases as the phase difference increases, while the lateral impact intensifies. Additionally, the wheel-rail creep characteristics and wear power between the wheel and rail are significantly affected. Moreover, when there is a phase difference in the 3rd-order wheel polygon, the speed increase is more sensitive to the influence of the wheel-rail creep characteristics, increasing the wheel-rail wear power and exacerbating the formation of wheel polygons. When the 25th-order wheel polygon has a phase difference, especially around half the phase difference period, the fluctuation range of wheel-rail forces is considerable, significantly affecting the wheel-rail creep characteristics and resulting in the greatest fluctuation range of the wear power, thereby further aggravating the wear evolution of the wheel polygon. The existence of the phase difference aggravates the wear rate of the wheel on one side and changes the wear position of the wheel. It is recommended to repair it in time.

By using 2,3-epoxypropan-1-ones and arylamine, boron trifluoride acetic acid complex/acetylacetone-promoted in situ ring opening-aryl migration reaction at 80 ℃ was developed in 1,4-dioxane, synthesizing a series of N-aryl enaminones in good yields. The structures of all products were characterized by ¹H NMR, HRMS and IR spectra. In addition, the structure of compound 3 was further confirmed by single-crystal X-ray diffraction analysis.

The presence of fog severely reduces the image quality and hinders further image processing as well as the corresponding feature information extraction. An end-to-end image defogging algorithm based on a multi-scale hole residual block and multi-scale attention mechanism is proposed to address the problems of inadequate feature extraction of existing defogging algorithms. First, the shallow features of the fog map were extracted by three small-scale convolution kernels, which can obtain a large receptive field and reduce the number of parameters. Then, it was input into a plurality of network modules composed of a multi-scale residual hole convolution feature extraction module and multi-scale attention mechanism module in series, in which the multi-scale hole convolution residual feature extraction module could extract the fog map features of different receptive fields and fuse the features of different dimensions to effectively solve the problem of single feature scale, while the multi-scale attention mechanism module reasonably allocated the weights of different features and suppressed irrelevant redundant information. Finally, the fog features in the fog map were filtered to obtain the feature map of the defogging map, followed by restoring the fog-free image using convolution operation. By testing on the sots test set, better visual effects are obtained compared with other classical methods, and the performance on PSNR and SSIM is also better than other classical methods.

As one of the core components of electric vehicles, IGBTs' health monitoring and remaining life prediction play a vital role in proactive maintenance. The Bi-LSTM model based on Bayesian optimization and attention mechanism is proposed to predict the remaining useful life of IGBT in this paper. The proposed method can effectively improve the accuracy of IGBT remaining service life prediction. V_CE-on through IGBT accelerated aging test is collected in this study, verifying its feasibility as a failure characteristic parameter. This data is used as an experimental data set to validate the proposed method through simulation. The experimental analysis results show that the proposed hybrid prediction model has lower degradation prediction error than the classical LSTM and other prediction models, demonstrating significant theoretical and practical value.

In response to the challenges posed by convolutional neural network (CNNs) commonly used for hyperspectral image classification, namely, their high parameter count, extended training times, and sensitivity to sample quantity, a classification network MDSR&SE-Net based on improved squeeze and excitation network and depth-separable residuals was proposed for limited training samples. First, the principal component analysis is employed in this model to reduce the dimension of the original HSI. Then, the multi-feature residual structure is connected by 3D convolutional neural network, and the spatial & spectral details of hyperspectral images are extracted by embedding the improved squeeze and excitation block. Finally, the extracted feature information is input into Softmax classifier to activate classification. To further lightweight the network, the number of parameters is reduced by using the depth separable convolution in the residual structure and introducing global average pooling. Experimental results show that overall accuracy of the three common hyperspectral data sets with the limited training samples are above 99%.

Aiming at addressing challenges such as the extensive data requirements for feature extraction, prolonged model training times, and reduced computational efficiency in present assessment, a method for evaluating transient voltage stability in wind power integration systems is proposed based on the combination of kernel principal component analysis(KPCA) and chaos particle swarm optimization (CPSO) and back-propagation (BP) neural network. Firstly, the raw feature set is collected according to the input features, followed by nonlinear data processing using KPCA to extract the optimal feature set. Then, the reduced dimension feature set is used as the input of the CPSO-BP neural network for supervised learning. The obtained model is categorized according to the margin of critical fault removal time. The classified samples are used for transient voltage stability evaluation and critical fault removal time margin prediction of wind power grid-connected systems. Finally, the simulation analysis results show that reducing the dimension of the input features, retaining the important input features, and eliminating the redundant features, not only simplifies the model but also improves the accuracy and calculation efficiency of network evaluation.

Based on the Python program, two mechanical objects, discontinuous displacements of bar element and ideal rigid rods, are associated and unified. Then the finite element model analysis of the planar bar system structure is carried out, and a computational mode of centralized processing of degrees of freedom based on “variable tagging” is realized. Based on the principle of virtual work, the load transfer theorem of the rigid body is introduced and proved, which elucidates that within the finite element built-in algorithm, the process entails an inherent “stiffening” treatment of element stiffness matrices when handling coupled elements, rigid rods, and the omission of specific degrees of freedom. The analysis of a numerical example shows that the computational mode of “variable tagging” and the "stiffening" treatment of the element stiffness matrix have the characteristics of universality and unity of mechanical model, feasibility of programming, and reliability of results, which can solve the modeling problem of arbitrary bar structure in plane. The results show that “master-slave nodes”, “rigid rods” and other modeling methods have important participation value for advancing finite element methodologies, particularly in finite element secondary development, large deformation, and nonlinear functional expansion. Moreover, it is feasible to apply the Python program to structural finite element analysis.

In order to reveal the constant amplitude fatigue failure mechanism of bolt pin shaft in pin hinge joint of spatial structure and explore the influencing factors of fatigue strength, the fatigue test of M36 bolt pin shaft was carried out. Based on the self-designed loading device, the constant amplitude fatigue tests of 9 bolt pin shafts were conducted. The nCode fatigue simulation analysis software was used to do parameterized analysis of 32 models with 4 factors for fatigue simulation. The results shows that the maximum equivalent stress in the pin hinge joint appears at the junction of the inner and outer padeye and the bolt pin shaft, where the stress concentration is serious. Neglecting unfavorable factors such as initial defects of the specimen and experimental loading, the fatigue life obtained from numerical simulation is partially higher than the corresponding fatigue test life. The S-N curve and theoretical fatigue life estimation formula of the bolt pin shaft are obtained based on linear fitting. The constant amplitude fatigue strength of bolt pin shaft is positively correlated with the loading stress ratio and bolt diameter, negatively correlated with the initial growth of pin hole clearance, and has nothing to do with the ear plate spacing. The sensitivity order of influencing factors of constant amplitude fatigue performance of bolt pin shaft is: the gap of pin hole, the bolt diameter, the loading stress ratio, the ear plate spacing.

Relying on the bridge pile foundation project in the salt marsh area of the De Xiang Expressway in Qinghai Province. To investigate the influence of different corrosion damages on the bearing capacity of foundation pile in salt marshes, a response model of the vertical and horizontal bearing capacity of foundation pile was established using the response surface method, considering factors such as pile length, pile diameter, corrosion depth, and spalling thickness. The interaction between two factors was analyzed using response surface plots. The results show that the accuracy of the corrosion-damaged foundation pile bearing capacity model established by the response surface method is relatively high. The vertical bearing capacity increases with the increase of pile length and pile diameter, and the decrease of corrosion depth and spalling thickness. The horizontal bearing capacity increases with the increase of pile diameter and the decrease of spalling thickness, but first decreases and then increases with the increase of pile length. When the pile length is relatively small, the influence of corrosion depth on bearing capacity is relatively small, while the influence of spalling thickness is much greater. Therefore, attention should be paid to the protection against horizontal corrosion damages in engineering practice.

The consolidation settlement of soil has a great influence on negative friction acting on the sides of piles. Under the framework of unsaturated soil mechanics, based on the interaction principle of the soil-pile interface, a computation methodology for consolidation settlement of soil is proposed in this study. Firstly, according to the hydraulic equivalent principle of collapsible loess, the equivalent load after immersion is calculated. Subsequently, considering the consolidation characteristics of unsaturated soil, the governing equation of pore air and liquid under the equivalent load is established, and the formula for calculating the settlement of soil in the exhaust stage is deduced. Finally, the negative friction of the pile side is obtained according to the relationship between the settlement of soil around the pile, the axial force, and the negative friction. The rationality of the proposed method is then verified through relevant case studies. The results show that the proposed calculation method is feasible and enriches the calculation model of negative friction of the pile side.

The metal roof system is particularly sensitive to wind load, and the roof components are fixed by connectors, which is easy to cause connection failure under high wind loads. According to the stress distribution and failure mode of metal roof and connector under wind load, a novel snap-in type connector with free rotation capability puts forward. The rotation of the connector can offset the deformation of the roof and relieve the temperature-induced stress, rendering the whole roof system flexible and adaptable, so as to improve the anti-wind performance of the whole roof panel. The finite element model is established by the finite element software ANSYS, and the wind resistance bearing capacity and wind resistance failure mode of the new T-shaped connector is obtained. The effectiveness and rationality of the new T-shaped connector in enhancing the wind resistance of the metal roof system are verified by comparing it with the original T-shaped connector.

Based on strength subtraction,through practical project cases,the slope failure process under the three kinds of elastoplastic models w analyzed numerically to explore the slope surface deformation law in this process. The results show that the safety factor is obtained by the reduction coefficient corresponding to the deformation mutation point,which provides ideas for the study of the relationship between deformation and slope safety factor.And that conducives to the establishment of slope monitoring and early warning system,and is of great significance to the progress of slope engineering informatizationin the future.

Let R be an associative ring with identity, m and n be fixed positive integers. The notions of (m,n)-injective functors and (m,n)-flat functors are introduced. Some properties of these two classes of functors are studied and some equivalent characterizations for (m,n)-coherent rings and Von Neumann regular rings are given in terms of (m,n)-injective functors and (m,n)-flat functors.

The definitions of L-anti fuzzy subsemigroups and L-anti fuzzy Γ-subsemigroups are given, and the basic properties of L-anti fuzzy ideals of Γ-semigroups are studied. Furthermore, the necessary and sufficient conditions for L-fuzzy subsets of Γ-semigroups to be L-anti fuzzy bi-Γ-ideals are confirmed.

The modal inverse problem of constructing the stiffness matrix of a vibrating beam model from partial or missing modal information under certain constraints on the stiffness main submatrix of the system is discussed in this paper.The matrix equations are obtained from the characteristic information and are solved in three cases according to whether the given frequency data belongs to the system. Using the Newton-Kantorovich theorem and the basic theory of linear equations, the necessary and sufficient conditions for the existence of a unique solution to the inverse modal problem are obtained. The explicit expression and numerical algorithm of the solution are given. The convergence and numerical stability analyses of the corresponding algorithm are presented and proven. Combined with an engineering example, numerical experiments indicate the correctness of the theory and the effectiveness of the algorithm. Additionally, the computational process is shown to be numerically stable through further analysis.

Whether the (G,N) implication satisfies Modus Ponens, Modus Tollens, and Hypothetical Syllogism is discussed in this paper, and some criteria that (G,N)-the implication satisfies the corresponding inference rules under some common t-norms is given, which provides a reference for optimizing the design of fuzzy inference algorithm.

The multiplicity of periodic solutions for a class of second-order Hamiltonian systems with local superquadratic conditions is studied via the Symmetric Mountain Pass Lemma. Infinitely many critical points of the energy functional of the system are obtained. Under this local superquadratic condition, it is demonstrated that the second-order Hamiltonian system has infinitely many periodic solutions.