Abstract:In order to study the seismic performance of side joints in ancient-style double-beam-column structures,quasi-static tests were carried out on two steel joints connected by split-type unilateral high-strength bolts and T-stub connection between circular steel tube columns and H-shaped steel beams,with different T-stub connections thicknesses.Through the tests,the hysteresis curves,skeleton curves,stiffness degradation,energy dissipation,ductility and other seismic indicators of the joints were obtained.The influence of the thickness of the T-stub connectors on the failure mode,flexural bearing capacity,and rotational stiffness degradation of the double-beam-column joint was analyzed.The ABAQUS software numerical simulation was used to further investigate the influence of flange and web thickness of the T-stub connectors on joint performance.The results show that both joint specimens exhibit spindle-shaped hysteresis curves,with certain pinching phenomena.Due to the increase in the thickness of the T-stub connectors,the initial stiffness of the joints increased by 23.93%.In the parametric analysis,compared with increasing the web thickness of the T-stub connector alone,increasing the flange thickness had a greater influence on the joint.Properly increasing the flange thickness can more effectively improve the strength of the T-stub connectors.Therefore,this type of joint is more suitable for use in earthquakes.

Abstract:Duckbill terminals often degrade after multiple mating cycles.Key issues include significant wear,enlarged blade gap,higher contact resistance,and elevated temperature rise.This study combines theoretical analysis with indoor single-factor tests to examine how terminal spring arm(TSA)length(L)affects mechanical and electrical performance over multiple mating cycles.Results show that reducing the L amplifies changes in plug force,minimum gap of the spring arm,and surface roughness under different cycles.However,it also significantly reduces contact resistance(p<0.05).Terminals with L≤3.3 mm showed a noticeable resistance increase after 100 cycles.Still,their resistance remained much lower than those with L≥4.3 mm.After 500 cycles,terminals with L≥3.8 mm exhibited increased contact resistance.A longer TSA led to a slower rise in resistance over cycles.Although longer TSAs reduced wear and spring arm gap,contact resistance was higher.This indicates that TSA length affects contact resistance more than spring arm gap or surface roughness.To enhance plug force and maintain low contact resistance after multiple mating cycles of duckbill terminals,it is advisable to use a shorter TSA length—preferably L≤3.3 mm.

Abstract:The nonlinear and non-stationary characteristics of liquefied natural gas price series limit the forecasting accuracy of traditional models.To address this,a hybrid forecasting model is developed following the framework of"mode decomposition-sequence reconstruction-heterogeneous modeling-error correction."Specifically,variational mode decomposition is employed to decompose the original price series into multiple modes,which are then reconstructed into low-frequency and medium-frequency subsequences using sample entropy clustering.ARIMA and GRU networks with integrated attention mechanisms are applied to forecast these subsequences respectively,followed by XGBoost for secondary residual correction.Single-step rolling forecasting experiments on China's daily LNG ex-factory prices demonstrate that the proposed model outperforms all benchmark models,achieving a 44％reduction in MAE compared to the best baseline GRU-Attention,with the Diebold-Mariano test confirming the statistical significance of its forecasting superiority.Ablation analysis validates the effectiveness of the error correction module,while tests across different market scenarios further confirm the model's robustness.

Abstract:In order to solve the problem of excessive displacement of main girders and falling girders in small and medium-span girder bridges under strong earthquakes,a gap-type integrated energy dissipation and anti-falling girder device was proposed in this paper,with the aim of realizing the functions of energy dissipation and damping under small and medium-span earthquakes and limiting the position under strong earthquakes,as well as meeting the demand for small displacements caused by temperature effects in normal use.Firstly,the hysteretic behavior of the device was investigated through variable amplitude cyclic loading tests to analyze its energy dissipation effect.Then,the relationship between the damping force of the device and the loading rate was investigated by low and fast performance tests.After that,the fatigue performance of the device under seismic action was verified by fatigue tests.Finally,the effects of different friction materials on the mechanical properties of the device were investigated.The results show that the hysteresis curve of the proposed energy dissipating anti-falling beam device is full and the energy dissipation is stable.The polytetrafluoroethylene material shows better stability,and the damping force of the device is basically unchanged under various loading rates,but the damping force is smaller.On the contrary,the two selected polyester materials can produce large damping force,but damping force of the device decreases with the increase of loading rate,and the maximum decreases are 13.4％and 24.1％,respectively,and the damping force decreases by about 21.3％and 28.4％in fatigue tests.The proposed new anti-falling beam device,with obvious gap characteristics,reduces the requirement for durability of the friction material and can provide a more economical option for vibration damping limiters.

Abstract:To clarify the release characteristics of fumes under the coupling effect of multiple factors and solve the issues of low efficiency of single fume suppressant and unclear synergy mechanism,the emission patterns and gas components of fumes under various conditions were investigated in this study.The response surface method was adopted for multi-objective optimization design,and a multi-objective optimization model for fume suppression rate,penetration,softening point,ductility,and fume suppressant ratio was established.The optimal dosage was calculated,and the effect and synergy mechanism of the composite fume suppressant on asphalt were analyzed.The results show that the effect of stirring rate on the generation rate of asphalt fumes initially increases and then tends to be stabilized;with the rise in temperature,the generation rate of asphalt fumes is divided into three stages:slow growth,rapid growth,and subsequent slow growth.The amount of asphalt fumes produced varies with the extension of heating time.The fume emissions of 70# and 90# asphalt are higher than that of 30# asphalt,while the lowest fume release is exhibited by SBS modified asphalt.Both the quantity and composition of fumes released differ across various asphalt types.When the composite fume suppressant is formulated with a mass ratio of 4.38％magnesium hydroxide,2.19％expandable graphite,and 3％activated carbon,the fume suppression rate reaches 82.52％,the asphalt structure distribution is uniform,and the modification mechanism is dominated by physical effects.

Abstract:A butterfly-shaped gain-enhanced metasurface antenna structure employs a 5×5 array unit structure as an antenna radome.When positioned at an appropriate distance directly above the radiating antenna,it significantly enhances both the gain and operating bandwidth of the microstrip patch antenna.The radome optimizes the radiation direction by adjusting the phase distribution and redistributing the energy of electromagnetic waves.The metasurface structure achieves uniform phase allocation through rectangular slots and triangular cuts,thereby concentrating the radiation beam energy more effectively and significantly enhancing gain.At the central frequency of 5 GHz,the antenna gain increases from 7.33 dBi to 16.24 dBi,while the operating bandwidth expands from 4.81～5.09 GHz(5.6％)to 4.66～5.09 GHz(8.0％).The radome can also be extended to other types of antennas,enabling bandwidth broadening and radiation gain enhancement for specific antenna systems.

Abstract:Dairy cow teat parameters are an important part of linear scoring.However,due to the small teat target and complex morphology of teats,achieving the rapid and accurate detection of multiple teat parameters remains challenging.This paper proposes an automatic detection method of dairy teat linear scoring parameters based on the improved PointNet++network model.Firstly,the Kinect DK camera was used to obtain the RGB-D data of the dairy cow scene,and the three-dimensional reconstruction was realized based on the ORB-SLAM2 algorithm fused with depth information.Secondly,in view of the characteristics of small teat target and difficult segmentation of dairy cows,the Heatblock attention mechanism was introduced to improve the segmentation accuracy of PointNet++network model.Finally,point cloud processing and principal component analysis were used to calculate the parameters of teat length,height difference between front and rear udders,and distance between front and rear teats.The results show that the segmentation accuracy of the improved model reaches 95.7％,with an average intersection over union of 80.2％,and the error of the parameters of the cow's teat is less than 3.85％.The method has the characteristics of high degree of automation,high precision and low stress on dairy cows,which can meet the requirements of automatic detection of dairy cow teat parameters.

Abstract:To investigate the improvement effect of cement on Luoyang expansive soil,and to reveal the strength degradation laws and crack evolution characteristics under wet-dry cycles,indoor experiments were conducted on Luoyang expansive soil with different cement ratios under dry-wet cycles.The grey relational degree and random forest methods were introduced to establish a macro-meso analysis model for expansive soil.The results indicate that the incorporation of cement alters the composition of Luoyang expansive soil and significantly reduces the free swelling rate.When the cement content reaches 6％(mass fraction),the expansive soil is transformed into non-expansive soil.With the increase in cement content,the compactness,unconfined compressive strength,and elastic modulus of the expansive soil first increase and then decrease,and the failure mode of the specimen transitions from plastic to brittle failure.As the number of dry-wet cycles increases,the strength and elastic modulus of the improved expansive soil exhibit a nonlinear decreasing trend and eventually stabilize.The optimal cement content is determined to be 6％.Analysis reveals that crack indicators are significantly correlated with compressive strength,with the mean crack width showing the strongest correlation.A random forest model was established for regression analysis,and the model demonstrated high accuracy and excellent performance in prediction.

Abstract:In order to improve the combustion efficiency of methanol swirl burners and reduce NO emissions,the combustion state and NO emissions of methanol swirl burners were investigated through numerical simulation.The results were compared and optimized with experimental data.A laser particle size analyzer was used to examine the atomization effect and droplet size distribution of methanol spray.This provided the spray size parameters for the discrete phase model of methanol droplets in the numerical simulation.The results show that the simulated spray size closely matches the experimental data.The study focuses on analyzing the effects of different blade angles on velocity distribution,temperature distribution,and NO mass concentration in the combustion chamber.The results indicate that as the blade angle increases,axial velocity of the gas mixture is suppressed.Stable recirculation zones are formed in the combustion chamber at blade angles of α=40° andα=60°,significantly improving the mixing of methanol and air.Regarding temperature distribution,under small blade angles,high-temperature zones are concentrated but relatively low in temperature,with noticeable low-temperature regions at the bottom.Under large blade angles,high-temperature zones expand,temperature increases significantly,and bottom temperature uniformity improves.Combustion efficiency improves as blade angle increases,but the improvement weakens when the angle exceeds 40°.NO generation concentration in the combustion chamber and at the outlet rises with increasing blade angles.The swirl vane angle significantly affects velocity,temperature,NO distribution,and combustion efficiency in the combustion chamber.The optimal performance is achieved at α=40°.

Abstract:To address the issues of large draught force and high energy consumption in moldboard plow tillage,the scale structure of pangolins and the dermal denticle structure of sharks were taken as bionic prototypes to design a coupled bionic moldboard plow body surface.Based on the Moore-Coulomb soil shear theory,the composition and action mechanism of draught force were clarified through theoretical analysis,with a focus on bionic drag reduction targeting the frictional resistance between the soil and the surface of the plow body.The drag reduction effect of the coupled bionic moldboard plow body surface and the reliability of simulation results were verified through a combination of discrete element method simulation and field experiments.The simulation results show that under a tillage speed of 1.5 m·s-1 and a tillage depth of 150 mm,the coupled bionic moldboard plow reduces draught force by 14.75％,and increases the soil disturbance area by 4.22％compared with the traditional moldboard plow.This indicates that the coupled bionic plow body significantly reduces draught force while ensuring effective soil disturbance.The field test results show that the coupled bionic moldboard plow reduces draught force by 13.57％and increases the soil disturbance area by 2.62％compared with the traditional moldboard plow.The field test results are highly consistent with the simulation test results,which verify the drag reduction effect of the bionic design and the reliability of the simulation model.The research results provide a theoretical basis and technical solution for the surface drag reduction design of single large-width moldboard plow body.

Abstract:Traditional manual inspection suffers from issues such as inconsistent standards and susceptibility to fatigue interference.However,existing deep learning methods based on real-time object detection algorithms tend to lose feature details due to downsampling operations and exhibit high computational complexity,making it difficult to meet precise detection requirements.To address these challenges,this paper proposes a lightweight high-resolution network detection method for metal surface defects.This method preserves subtle defect signals through a full-process high-resolution feature preservation architecture,achieves a lightweight design by integrating depthwise separable convolutions,introduces a conditional channel weighting mechanism to optimize multi-resolution feature fusion,and proposes a global spatial feature extraction method to enhance contextual correlation.Experiments show that the network achieves mAP50 scores of 79.6％and 70.9％on the NEU-DET and GC10-DET datasets,respectively,with a parameter count of only 5.3M and 7.1 GFLOPs.When tested on a dual RTX 4090 GPU setup,it reaches a frame rate of 117 FPS.Compared with previous benchmark models,the proposed method demonstrates significant advantages in both detection accuracy and computational efficiency.Ablation experiments verify the effectiveness of each module,providing a high-precision and low-power solution for real-time industrial detection of metal surface defects.

Abstract:In order to address the problem of incomplete images and severe deformation and ghosting in the stitching of cylindrical labels on penicillin bottles,a cylindrical label image stitching method based on cylindrical correction and weighted fusion was proposed.Firstly,the curved label image was unfolded using a cylindrical correction algorithm,and the overlapping area of the label image was roughly extracted using a phase correlation algorithm.Then,the speeded up robust features(SURF)algorithm and random sample consumus(RANSAC)algorithm were used to extract feature points in the overlapping area and eliminate mismatched points,respectively.Finally,combining the dynamic programming suture search criteria and nonlinear weighted fusion algorithm,seamless stitching of cylindrical label images of penicillin bottles was achieved.The experimental results show that this algorithm not only accelerates the speed of image registration,but also effectively avoids the generation of ghosting and stitching lines.It can effectively unfold label images of curved surfaces,greatly improve image quality,and contribute to the extraction of cylindrical label information.

Abstract:Based on the project of Xiaotun Bridge of Fuyi Expressway,the key technologies involved in the integral intelligent lifting of large-span heavy steel box girders were discussed.The mechanical properties of steel box girders in both synchronous and asynchronous integral lifting states were investigated using the finite element method.And the mechanical properties of the steel box girders during the lifting process were analyzed in conjunction with the on-site monitoring data.In conjunction with construction techniques such as informal lifting and micromotion lifting,an integral intelligent lifting scheme for steel box girders was proposed to address extreme conditions.An alignment system has been incorporated into the existing synchronous lifting hydraulic system,enabling precise control over the aerial orientation of the steel box girder and the stresses on each component.This approach offers valuable insights for similar projects.

Abstract:By delving deeply into the research themes of journals and forecasting academic development trends,researchers can more precisely grasp disciplinary directions and keep pace with cutting-edge dynamics.However,journal abstracts,being short texts,present significant challenges to traditional topic modeling methods due to their structured characteristics,high-dimensional sparse vector representations,semantic structural complexity,and data noise.To address this issue,this paper proposes a BERTopic-based model for topic evolution analysis.This model integrates the strengths of pre-trained language models in semantic representation with the structural modeling capabilities of hierarchical clustering algorithms.It also reconstructs the term weighting strategy by introducing a sublinear transformation mechanism for term frequency to optimize traditional term weight calculation methods.This effectively mitigates the interference of high-frequency terms,highlights terms that are critical for distinguishing topics,and significantly enhances the model's topic discriminability and semantic representation capabilities.Using the journal Assessing Writing as the research object,this paper conducts an empirical analysis of research achievements in the field of writing assessment across different periods.By systematically organizing research themes and development directions at each stage,it reveals the dynamic evolutionary patterns of these themes.The experimental results demonstrate that this method can accurately capture changes in research hotspots within the field of writing assessment,clearly reveal its developmental trajectory,and exhibit good practicality and effectiveness in handling short-text data such as journal abstracts.It provides reliable technical support for academic research and trend forecasting in related fields.

Abstract:To ensure the welding quality of hot-melt joints of high-density polyethylene(HDPE)pipe,this paper proposes a total focusing method algorithm based on the time reversal algorithm and instantaneous phase coherent weighting factor.The method first processes signals through the time reversal algorithm,then extracts the instantaneous phase from the signals to construct the instantaneous phase coherent weighting factor,and weights the amplitude of each pixel of the total focusing imaging.Imaging detection experiments are carried out on φ1 mm,φ2 mm,and φ3 mm transverse through-hole defects in HDPE test block and φ3 mm hole defects in HDPE pipe butt fusion joint specimens.The experimental results show that the proposed algorithm can effectively suppress background noise and artifacts,reduce the amplitude of near-field noise(0～10 mm depth)and artifacts by about 30 dB,improve the resolution of total focusing imaging.Compared with the TFM algorithm,the average signal-to-noise ratios of the four defects are improved by 9.6 dB,11.8 dB,4.9 dB,and 3.5 dB,respectively,and the average array performance indicators are reduced by 56％,49％,38％,and 48％,respectively.This provides an effective improved scheme for the ultrasonic phased array detection of defects in butt fusion joints of HDPE pipe.

Abstract:As a tertiary relict plant species,Cercidiphyllum japonicum holds significant ecological and scientific value,yet faces conservation urgency due to its endangered status and challenges in natural regeneration.The MaxEnt model was employed to predict the future potential distribution patterns of Cercidiphyllum japonicum using 75 occurrence records and 19 bioclimatic variables,while analyzing climate change impacts on its habitat in this study.The results show that the MaxEnt model demonstrate excellent predictive accuracy(AUC=0.986),with precipitation of the warmest quarter(Bio 18),temperature seasonality(Bio4),and precipitation seasonality(Bio15)identified as dominant factors influencing distribution.Current suitable habitats are concentrated in central-southern China(22.0°～34.3° N,98.3°～121.6° E),covering approximately 3.12×106 km2,with highly suitable areas accounting for 33.65％.Under future climate scenarios(RCP2.6 and RCP8.5),suitable habitats will experience continued contraction(up to 10.58％reduction),distribution centroid shift southeastward,and notable contraction of highly suitable areas.The study provides scientific support for habitat conservation and climate change adaptive management of Cercidiphyllum japonicum,suggesting that priority should be given to enhancing conservation efforts in newly identified potential suitable regions along the southeastern coast while optimizing management strategies for existing protected areas.

Abstract:A closed-loop heat pump drying system based on air heat recuperation was designed to enhance drying performance.To optimize system efficiency,adjustable parameters during the drying process were investigated.Multiple experiments were conducted to analyze the effects of bypass ratio,drying chamber temperature,and circulating airflow velocity on the recuperation system,and performance comparisons were made with a non-recuperative system.The experimental results indicate that each of these three factors,including bypass ratio,drying chamber temperature,and circulating airflow velocity,has an optimal value.The recuperation system improved the specific moisture extraction rate(SMER)by 5.57％～37.40％,depending on the conditions.Compare with the non-recuperative system,the optimized recuperation system achieve an SMER enhancement of 7.71％～22.78％.

Abstract:Accurate modeling between physical devices and digital twins in industrial digital twins requires synchronizing massive amounts of sensing data.This results in difficulty ensuring real-time virtual-physical mapping.To address this issue,this paper proposes a four-layer bidirectional closed-loop architecture suitable for digital twins,consisting of a device,federated,cloud,and application layers.We develop a distributed federated bucketized decision tree algorithm utilizing histogram-based gain for global aggregation based on this architecture.Additionally,we design a pruning algorithm with adaptive gradient-weight redistribution to accelerate model convergence.Experimental results on the dataset demonstrate that the proposed federated aggregation model achieves accuracy improvements of 10％,11％,and 22％compared to baseline methods.It also achieves convergence improvements of 15％,20％,and 27％.Moreover,the proposed model maintains additional communication overhead within 300 mJ,even under the worst channel conditions.

Abstract:Aiming at the damage monitoring problem of typical marine composite material structures,a new method for monitoring the damage location of composite materials is proposed,and the relationship between static loading load and damage expansion coefficient is established.For damage location monitoring,based on signal spectrum and correlation coefficient,a Bayesian-based damage probability imaging method is proposed,and a multi frequency weighted damage imaging update method is proposed.For damage expansion research,three damage expansion coefficients are constructed according to the time-domain signal characteristics of ultrasonic guided waves and hyperbolic tangent function,and the damage expansion coefficients under different static loading loads are obtained.Experimental results show that the Bayesian-based damage probability imaging method can accurately locate the damage location;the variation law of damage expansion coefficient with increasing load provides technical support for the damage expansion of typical composite material structures.