To investigate wideband transparent 3D-printed Si₃N₄ antenna enclosures, this study employed Stereolithography (SLA) 3D printing technology to fabricate Si₃N₄ samples and conducted electromagnetic performance testing. Computational simulations were then utilized to evaluate the electromagnetic performance of solid structures, honeycomb structures, and gradient honeycomb structures of Si₃N₄ with varying thicknesses in the Ku(12~18 GHz) and Ka(27~40 GHz) frequency bands. The results revealed that thickness and microstructure design significantly influence the electromagnetic properties of Si₃N₄materials,and the transmittance of the honeycomb Si₃N₄ porous structure was significantly enhanced. Furthermore, by implementing a gradient design, the gradient honeycomb Si₃N₄ porous structure reduced the reflection of electromagnetic waves at the interface, achieving a gradual transition of impedance. Its transmittance exceeded 80% in the Ku(12~18 GHz) and Ka(27~40 GHz) frequency bands, with an extremely low energy loss rate (below 3%) across the entire frequency range.

The friction stir technique was used to connect copper and aluminum with low melting points. The diffusion ability of copper and aluminum atoms at the interface affects the mechanical properties of the interface. Molecular dynamics was used to study the diffusion behavior of atoms at the Cu/Al interface during friction stir welding, and the mechanical properties of the interface were assessed under different strain rates. The results showed that the quantity of copper atoms diffusing into the aluminum lattice is much larger than that of aluminum atoms diffusing into the copper lattice. The atom diffusion is dominated by the nearest-neighbor hopping mechanism with diffusion activation energies of 0.58, 0.75 eV for Cu and Al atoms, respectively. The thickness of the interface transition layer is mainly controlled by the holding temperature with the optimal thickness interface at 800 K. The maximum interfacial tensile strength is 3.19 GPa at the tensile strain rate of 1×10¹⁰s^－1. Plastic deformation primarily occurs within the aluminum side with minimal plastic deformation on the copper side. Dislocation reaction during the deformation process includes the decomposition of perfect dislocation and the formation of stair-rod dislocation. The dislocation energy decreases with the Shockley dislocation being the main slip dislocation.

The greenhouse effect caused by CO₂ emissions from fossil fuel combustion is becoming more and more serious, it is urgent to develop adsorbents with CO₂ adsorption properties. As new adsorbents, metal-organic frame materials (MOFs) and graphene oxide (GO) have the problem of low CO₂ adsorption performance. ZIF-8@GO was prepared by solvothermal method, and the microstructure and adsorption properties of ZIF-8@GO to CO₂ were studied by XRD, SEM and BET. The results showed that ZIF-8@GO maintains the crystal structure of ZIF-8, and GO mainly plays a role in size regulation and structure orientation of ZIF-8. The gas adsorption separation test showed that ZIF-8@GO is the same as ZIF-8, which is dominated by micropores. Notably, when the GO participation ratio is 8%, the BET and Langmuir specific surface areas of ZIF-8@GO(8%) materials are 1 037.18, 1 115.90 m²/g, respectively, and theadsorption capacity to CO₂ is 34.347 cm³/g. Compared with the parent ZIF-8 material, the CO₂ adsorption capacity is increased by 32.3%.

The coupled freeze-thaw cyclic corrosion tests of Na₂SO₄ solution with concentrations of 5%, 10%, and 15% were designed. The effect of glass powder on the corrosion resistance of concrete was analyzed, the effect of Na₂SO₄ solution concentration on the corrosion rate of concrete was revealed, and the effect of glass powder on the pore structure and interface transition zone (ITZ) properties of concrete was studied. The results showed that the glass powder significantly improves the corrosion resistance of concrete at a dosage of 0~10%, while the glass powder deteriorates the corrosion resistance of concrete when the dosage is greater than 15%. At the same time, when the concentration of Na₂SO₄ solution is greater than 7.5%, C_b, i_m, and S all increase with the increase of the concentration of Na₂SO₄ solution, which shows that the corrosion effect of Na₂SO₄ solution on concrete is enhanced with the increase of the concentration. After adding 5% and 10% glass powder, ITZ split tensile strength of concrete increases by13.17% and 10.89%, respectively, while ITZ width decreases by 15 μm and 5 μm, respectively compared with ordinary concrete.

In order to investigate the influence of stress gradient on the fatigue life of notched parts and to assess the fatigue life of notched parts with different failure probabilities, a new fatigue life prediction method based on Weibull distribution is proposed. First, the maximum strain energy density is defined as the damage parameter, and the location of the critical plane reflecting the crack initiation and expansion is determined by combining the coordinate transformation principle. Secondly, the stress distribution of a specific path on the critical plane is extracted by using the finite element method, which is then normalized to obtain the multiaxial equivalent stress gradient factor. Meanwhile, based on the GSP strain energy density model, an appropriate strain energy density model is selected, and the linear relationship between the strain energy density and the experimental life can be obtained. Finally, a new fatigue life prediction method is proposed based on the Von-Mises criterion by combining the equivalent stress gradient factor, the strain energy density model, and the Weibull distribution, which can be used to find the fatigue life at 10%, 50%, and 90% failure probability respectively. In order to verify the accuracy of the proposed model, the calculation results of this paper are compared with those of the SWT model, the FS model, and the Manson-Coffin equation, demonstrating a high degree of precision in the predictions.

The milling force is an important process parameter in the milling of thin-walled aluminium alloy parts, with accurate feedback playing a significant role in reducing the deformation of the work pieces. In order to achieve the accurate prediction of milling force, firstly, the milling force data was obtained through simulation tests for the milling of thin-walled aluminum alloy parts. Secondly, to address the drawbacks of the traditional BP neural network, the Lion Swarm algorithm was used to improve it. The milling force data was imported into the improved network for training, to establish the LSO-BP prediction model. Finally, the LSO-BP model, PSO-BP model, and the traditional BP neural network model were used to predict the milling force respectively. The comparison results of evaluation indexes such as root mean square error, average relative error, and correlation coefficient show that the LSO-BP model significantly outperforms both the PSO-BP model and the traditional BP neural network model in predicting the milling force.

In order to analyze the noise characteristics and the location of the specific sound source of the axial variable piston pump, a noise and vibration test of the pump was carried out by building a noise and vibration test bench. When the rotating speed was at a constant speed of 1 660 r/min and a fixed displacement of 75 mL/min, the noise and vibration signals of the pump were measured and recorded at load pressures of 16, 20, and 24 MPa, respectively. The collected signals were subsequently analyzed by means of spectral analysis and partial coherence analysis to obtain the noise characteristics of the pump and accurately trace the location of the sound source of the pump. The results show that the noise of the pump increases with the increase of the load pressure. The reciprocating impact of the piston, oil flow backward, and the pulsation of oil were the main noise sources of the pump under test. The noise caused by bearing vibration and spindle rotation was the secondary noise source. When the characteristic frequency was less than 200 Hz in the low frequency band, the main structural noise source of the pump under test was the vibration of the spindle rotation and the noise generated by the reciprocating movement of a single plunger. Conversely, when the characteristic frequency was above 200 Hz in the middle and high frequency band, the main structural noise source of the tested pump was the vibration caused by the plunger reciprocating movement.

Aiming at the lightweight design of automobile structures, a design method for automobile structure's reliability with uncertain manufacturing accuracy is proposed. The main design variables are regarded as interval variables, while other design parameters are regarded as probability values. On this basis, the reliability design method with uncertain manufacturing accuracy of automobile structures is established by using the transformation method of interval models and the decoupling strategy of probability models. The optimal solution and the maximum allowable deviation ranges under different reliability requirements are obtained through example analysis, which verifies the effectiveness of the method. The optimized design results show that the optimal variables and the corresponding maximum allowable deviation range can be obtained under acceptable manufacturing conditions. By appropriately increasing the deviation range of design variables, the requirements for manufacturing accuracy can be reduced, thereby reducing manufacturing costs.

For the high-energy-density power batteries of electric vehicles, a double-layer serpentine channel cold plate on the battery bottom is proposed for a nickel-cobalt-manganate lithium battery module in order to improve the batteries thermal management and ensure their safety. The optimal coolant flow scheme is the first scheme and the optimal channel width is 10 mm determined by numerical simulation.The influences of coolant mass flow rate, battery’s discharge rate and ambient temperature on the maximum temperature, temperature difference of battery module, and coolant pressure loss were analyzed successively. The results show that with the increase of discharge rate and ambient temperature, both the maximum temperature and temperature difference of the module increase. Increasing the flow rate of coolant can effectively control the maximum temperature of the battery, but this comes at the cost of increased pressure loss. Notably, when the discharge rate is less than 0.7 C, it is no longer necessary to start the liquid cooling system.

To avoid strength damage and improve the service life of LNG aluminumplate-fin heat exchangers, the tensile fracture mechanism of their aluminum plate-fin structures atroom/low temperature is studied using axial tensile testing and scanning electron microscope observation. The result shows that, compared to mechanical properties at room temperature, the yield limit of plate-fin specimens atlow temperature increases by 42.6%, the tensile strength increases by 48.9%, and the strain increases by 27.8% during failure. The fracture trend of plate-fin specimens at room/low temperature conditions primarily involved crack propagation from the fin root and vice versa. The overall fracture morphology of cleavage sections and dimples account for a large area of fracture surface. However, the morphology of cleavage sections is observed with high distribution at low temperature, and the plastic morphology accounts for a small area of fracture surface. The fracture of plate-fin specimen at room temperature is mainly located in the brazing zone, whereas the fracture at low temperature is confined to the brazing zone. Therefore, the fracture of the aluminum plate-fin structure in the brazing zone can be avoided by improving the brazing process of the aluminum plate-fin structure and increasing the solder in the brazing zone.

In the radar observer trajectory planning (OTP) of the target tracking process, for the intelligent decision-making problem of Markov stepping planning, a radar trajectory planning method based on the Monte Carlo policy gradient (MCPG) algorithm is proposed in the discrete action space. First, the OTP process is modeled as a continuous Markov decision process (MDP) by combining the target tracking state, reward mechanism, action plan, and radar observer position. A global intelligent planning method based on MCPG is then proposed. Next, by considering each time step in the tracking episode length as a separate episode for policy updates, a step-wise intelligent planning method based on the observer trajectory in MCPG target tracking is proposed. Then, the tracking estimation characteristics of the target are deeply studied, and a reward function for the purpose of tracking performance optimization is constructed. Finally, the simulation experiment of the intelligent OTP decision-making based on reinforcement learning in the optimal nonlinear target tracking shows the effectiveness of the proposed method.

In this paper, the design problem of H-infinity robust control is investigated for networked systems with access constraints and packet dropout. Firstly, the Bernoulli random process is utilized to describe the packet loss process of the networked system, and a discrete-time Markov jump system model is established according to the random-access mechanism of medium access constraints. Secondly, sufficient conditions for stochastic stability of the closed-loop system are derived by using Lyapunov stability theory and LMI technology. Correspondingly, H-infinity robust controller is designed to render the closed-loop system stochastic stability with the given H-infinity performance. Finally, an example is given to verify the correctness and effectiveness of the proposed control method.

Wind power has strong volatility and randomness, and the changes in unit monitoring data are complex. In order to improve the accuracy of wind power prediction, a wind power prediction feature selection method based on multi-information metrics fusion (MIMF) is proposed. Based on the analysis of three typical feature selection methods, including decision tree, L₁-regularization, and recursive feature elimination, it was determined that while decision trees offer clarity in expressing feature importance, L₁-regularization mitigates overfitting, and recursive feature elimination accounts for inter-feature correlations. Leveraging the strengths of these methods, a composite feature selection framework was devised, wherein the union of features selected by each technique is further refined based on their respective intercorrelations. Subsequently, the constructed feature selection method fused with multi-information metrics is simulated and analyzed. The simulation results on the measured data of a wind farm show that compared with the single feature selection method, this method can effectively improve the prediction accuracy of wind power.

Based on the single resistor tuned Wen-bridge oscillator, first, the oscillation conditions and oscillation frequency of the oscillator are derived. Moreover, two design schemes of the second-order band-pass filter are given. The advantage of the first design scheme is that the pole frequency can be adjusted by a single resistor, while the advantage of the second scheme is that the pole frequency and quality factor can be adjusted separately. Both schemes can realize two band-pass outputs and adjust the resistance to make the circuit oscillate, which the oscillation conditions and oscillation frequency can be adjusted separately. The designed circuit is proved to be correct and effective by computer simulation.

In order to overcome the limitations of traditional radio frequency self-interference cancellation (SIC) technology due to electronic bottlenecks such as frequency, bandwidth, and resistance to electromagnetic interference, and to meet the development needs of future wireless communication and radar systems, a microwave photonic self-interference cancellation scheme based on polarization multiplexed Mach-Zehnder modulator (PDM-MZM) is proposed. This scheme introduces a reference signal that is of the same frequency, amplitude, and phase as the self-interference signal and directly cancels it in the optical domain. Besides self-interference cancellation and down conversion functions, this scheme can also be used for IQ demodulation of vector signals. During IQ demodulation, the polarization controller in both channels can be flexibly adjusted to make the amplitude of the IQ signals strictly equal and the phase strictly orthogonal, thereby eliminating the impact of IQ amplitude imbalance on the receiving end of the full duplex system. Theoretical analysis and simulation testing were conducted in the article, and the results showed that the elimination depth of self interference signals can reach over 72 dB, and the SFDR of the system can reach 95.2 dB·Hz ^2/3, with a gain of －16.2 dB. This scheme has advantages such as large bandwidth, tunability, strong resistance to electromagnetic interference, small size, and low loss, and has great potential for application in wireless communication and radar systems.

For steel fiber reinforced self-compacting concrete (SFRSCC), the fiber content is one of the important factors affecting its performance. In order to investigate the influence of the steel fiber content on the performance of SFRSCC, six sets of specimens with different proportions of steel fiber were designed and fabricated to test their workability and mechanical performance under axial compression.The results show that the addition of steel fiber effectively delays the crack development, increases the peak strain of SFRSCC. The equivalent compressive toughness index increases with the increase of fiber content. The addition of steel fiber reduces the fluidity of freshly mixed concrete, and the shape factor related to rheological behavior of SFRSCC is less than that of ordinary self-compacting concrete (SCC). The addition of steel fiber has little influence on the compressive strength of SFRSCC. With the increase of steel fiber content, the compressive strength of SFRSCC decreases first and then increases.

The earth temperature mainly depends on meteorological factors such as atmospheric temperature, solar radiation intensity, rainfall, and air humidity. Taking the hilly and gully region of the western Weihe River basin in the Loess Plateau as the research area, a field observation site was established. The response of ground temperature of the shallow zone of aeration in situ to climate change was monitored in real-time. Through field monitoring data and theoretical analysis, it is found that the distribution law and change mode of soil temperature are as follows: meteorological factors only affect the soil temperature in the variable temperature zone, with the atmospheric temperature and solar radiation intensity being the main influencing factors. The deeper the soil layer, the lesser the impact. The phase of soil temperature shifts linearly with the depth of the soil, which means that the soil temperature has a hysteresis effect with depth. Analysis shows that the phase of the temperature curve of the soil at a depth of 760cm is exactly opposite to that at the surface, where the temperature lags behind the surface for half a year. Monitoring data predicts that the depth of the constant temperature zone in this area is 1193cm with a temperature of 13.152℃. When calculating the theoretical lag time of the soil temperature, the thermal diffusivity of the soil is regarded as a constant. It will cause discrepancies between theoretical and observed values, with the difference diminishing with increasing soil depth.

Considering the effects of various factors on inner-bracing stiffness, including the initial deflection, the second-order effect of compression and bending in the inner-bracing, the interaction between the inner-bracing and diaphragm wall, the deformation of diaphragm wall, etc., an effective stiffness calculation method for the inner-bracing was put forward for diaphragm wall and inner-bracing system. Taking the excavation engineering of a Beijing subway station project as a case study, the excavation process was simulated with ABAQUS finite element software, incorporating both the current standard support stiffness and the effective support stiffness. The simulation results were then compared with the measured data. The results show thateffective stiffness calculation method for the inner-bracing accords with the real force and deformation state of the foundation pit support system.

To investigate the effects of cross-section size, beam length, number of stiffeners, and number of floors on the structural influence coefficient (R) and the displacement amplification factor (C_d) of eccentrically braced frames with replaceable double-channel shear links, incremental dynamic analysis (IDA) was conducted on 18 models with varying parameters using the OpenSees finite element software. The structural influence coefficients and displacement amplification factors were calculated for each respective model. The results indicate that the seismic performance and deformation capacity of the eccentrically braced frame with replaceable double-channel shear links can be enhanced through the judicious design of the shear link structural parameters. Additionally, proposed values of R and C_d are provided to serve as a reference for further studies on the structural influence coefficient of eccentrically braced frames.

Based on the measured data during the excavation of a deep foundation pit in Shenzhen, the physical and mechanical parameters of soil are obtained by back analysis program. After obtaining the soil parameters in line with the actual conditions, the finite element software ABAQUS is used for numerical calculation to analyze the influence of layered excavation on the deformation of foundation pit under seepage conditions, mainly including the uplift of the soil at the bottom of the foundation pit, the deformation of the foundation pit after excavation, and the underground. The deformation of the diaphragm wall and the permeability coefficient of the strong permeability soil layer are changed to analyze the deformation of the foundation pit. The back analysis program and finite element software are used to simulate the construction process of the actual project, and the simulation results are compared with the actual monitoring results. The results show that the deformation of foundation pit calculated by the combination of back analysis program and finite element software is closer to the actual situation. The change of permeability coefficient of strong permeability soil layer has the greatest impact on the uplift of soil at the bottom of foundation pit.

Based on a project in Lanzhou New District, this paper conducted a comparative study on the strengthening effect of compacted pile composite foundation with different pile types, such as plain soil compacted pile, SDDC compacted pile, and two kinds of compacted pile combination in collapsible loess area through a large number of tests to evaluate the bearing capacity of compacted pile composite foundation, the compaction coefficient of pile body soil, the compaction coefficient of soil between piles, and the collapsibility of loess. The results show that all three pile types of compacted piles can effectively improve the bearing capacity of the foundation and improve the collapsibility of loess. Plain soil compaction pile has limited ability to improve the bearing capacity of the foundation, with the soil compaction degree between piles greatly affected by the particle size of backfill soil, resulting in uneven densification. SDDC compaction pile has a better effect on improving foundation bearing capacity and settlement control than plain soil compaction pile.

The existence of positive solutions to a class of fractional integral boundary value problems with p-Laplacian operators is studied. By employing the fixed point theorem of mixed monotone operators, sufficient conditions for the existence of a unique positive solution to the boundary value problems are established. In addition, two specific examples are given to illustrate theoretical results.

By the Gauss theorem and Cauchuy-pompeiu formula in C, the Dirichlet problem and Neumann problem for higher order complex partial differential equations on the unit disc are discussed, and the integral representations and the conditions of the solutions are obtained, which lead to the conclusion of the boundary value problem for poly-analytic functions.

The r-component (edge) connectivity is used as an important reliability measure to analyze the reliability of the enhanced hypercube interconnection network, and the r-component (edge) connectivity is obtained. It is proved that cκ₂(Q_n,k)=cλ₂(Q_n,k)=n+1 for 2≤k≤n－1,cκ₃(Q_n,k)=2n,cλ₃(Q_n,k)=2n+1 for 4≤k≤n－1,cκ₄(Q_n,k)=3n－2 for 4≤k≤n－1, cλ₄(Q_n,k)=3n－1 for 6≤k≤n－1.