Latest ArticlesTo explore the process and evolution of large-scale flight delay propagation, and avoid previous research mainly focusing on observing real data and the distribution of delay propagation networks. Drawing inspiration from the classic susceptible-explored-infected-recovered(SEIR) model and taking into account the impact of node closure on large-scale flight delays. Based on this, the state of airport nodes was added to five categories, and a large-scale flight delay propagation model based on susceptible-explored-infected-death-recovered (SEIDR) was constructed and applied to air traffic networks. Using a combination of phase trajectory analysis and related parameter analysis, the propagation threshold and propagation law of large-scale flight delays were obtained, and the influence of propagation parameters between airport nodes on the propagation law of large-scale flight delays was further analyzed. Finally, a large-scale flight delay in 2022 was taken as an example for analysis and verification. The results show that the established model can more accurately describe the evolution process and propagation law of large-scale flight delays.
In practical production processes, equipment performance gradually degrades over time, leading to extended processing durations. To address this issue, an improved nondominated sorting genetic algorithm II (NSGA-II) was proposed for a re-entrant hybrid flow-shop scheduling problem that considers deterioration effects. Firstly, a mathematical model was formulated with the optimization objectives of minimizing makespan and reducing processing energy consumption. Secondly, a job-sequence-based encoding method was employed, and an energy-efficient scheduling decoding method that accounts for deterioration effects was designed. Additionally, to enhance population diversity, various mutation operators were introduced, and algorithm parameters were adaptively adjusted to prevent convergence to local optima. A variable neighborhood search strategy was also integrated to reinforce the local search capability of the algorithm. Finally, comparative experiments with other algorithms on ten different scale test instances demonstrated that the proposed algorithm delivers superior solution quality, along with better diversity and convergence properties.
Considering the technical issues related to the construction of extremely small radius and ultra large diameter shield tunnels in stratified strata, taking the shield tunnel project of the Pazhou Station to Beigang Park Station section of the Pearl River Delta intercity rail transit in Guangzhou as the research object, key construction technologies of shield excavation were elaborated in detail. Solutions to outward deviation of the excavation axis because of the small curve radius and strata disturbance caused by the excavation were provided. Built upon the analysis of on-site real-time monitoring data, variation patterns of vertical and horizontal displacements, pore water pressure and soil pressure during the construction of the small radius shield tunnel were revealed. Monitoring data shows that the shield excavation of the turning section in rock layers has little impact on surface settlements. The influence of shield tunneling on the surrounding soil decreases with the increasing distance, the maximum horizontal displacements occur in the area above the tunnel. There is a high similarity in the changing trend of pore pressure and soil pressure and the impact on the soil outside the turning is greater when the shield turns.
low-temperature fracture is the normal distress of the thin-layer overlay asphalt mixture. To reveal the low-temperature cracking behavior, semicircular bending tests combined with crack observation, digital image correlation and a finite element numerical simulation based on the meso-structure cohesive zone model were carried out. The applicability of the model was verified by the load-displacement curve and crack paths. The results show that the low-temperature cracking behavior of asphalt mixture can be well demonstrated by digital image processing. The simulation of asphalt mixture meso-structure is suitable for analyzing the cracking behavior. Furthermore, the maximum tensile stress and neutral axis positions on the mid-span section are correlated with the properties of the materials.
The bridge health monitoring system based on sensor data acquisition has become standard for new bridge construction. However, this scenario presents challenges due to the massive volume of monitoring data that is difficult to store. Therefore, focusing on the time-series characteristics of bridge monitoring data, compression schemes were explored for bridge monitoring data. Differential compression was investigated based on the arithmetic progression properties of bridge monitoring timestamps and floating-point exclusive OR(XOR) compression based on the low frequency of changes in monitoring value data. Compared to the Gorilla time series database algorithm, the XOR compression method added control bits to avoid degradation of compression results. Experimental analysis reveals that both algorithms exhibit varying degrees of superiority over common compressors. The differential compression of timestamp sequences demonstrates superior compression rates compared to common compressors, achieving a compression rate of 0.015 6 for timestamp sequences that conform to arithmetic progression characteristics, approaching the compression limit value. Compression and decompression speeds are above average, and the method is insensitive to monitoring type. On the other hand, the XOR compression method performs well on datasets with low frequency of change, achieving compression rates of 0. 302 8 for bridge data and 0. 662 8 for non-bridge data, indicating sensitivity of the XOR compression method to monitoring type. In practical applications of bridge monitoring, suitable compression storage schemes can be selected based on the characteristics of the bridge monitoring dataset.
The blowout preventer (BOP) is a key well control equipment, in which the shear ram BOP is the last line of defense against blowout accidents. Therefore, its shear performance under extreme working conditions is crucial for the safety of drilling operations. A super shear ram BOP was taken as the research object, and the numerical analysis was carried out by using the dynamics module. The simulation results were compared with experimental and theoretical values to verify the accuracy and applicability of the model. In order to investigate the influence of extreme working conditions on the shear capacity of the ram BOP, the shearing performance of the drill pipe joints was evaluated under high pressure working conditions, eccentric working conditions and moving conditions. The response surface method was applied to develop a shear force prediction model under extreme working conditions. Based on the prediction model and the actual shearing capacity provided by the ram BOP, the shearing failure scenarios under extreme working conditions were determined. The results show that the relative errors between the theoretical values and the simulation results are less than 3%. In the shearing process, the larger the axial tension and compression load, the more unfavorable the shearing. While the certain deviation distance is conducive to the shearing. The research results can provide technical guidance for preventing the shearing failure of ram BOP.
In order to reduce the vibration of fracturing branch pipe during fracturing operation, the fluid-structure coupling analysis method was used to carry out the modal analysis and harmonious response analysis of fracturing branch pipe, considering the impact of fracturing pump vibration and high-pressure fracturing fluid on fracturing branch pipe. The influence of angle of bend and number of fracturing branch pipe supports on fracturing branch pipe vibration was studied. The results show that under the current layout, the main vibration positions of the first six modal modes of the manifold appear at double elbows 2, 3, and 4, indicating that the main vibration deformation of the fracturing branch pipe occurs at its lower end, that is, at the double elbows far away from the fracturing truck. Considering the weak points at double elbows 2, 3, and 4, the smaller displacement response amplitudes of each double elbow at each connection angle are obtained based on the maximum displacement response amplitude. Indicating that each connection angle is the best choice for the actual fracturing operation. When four elastic supports are used, the maximum amplitude is much smaller than that of two or three elastic supports, indicating that adding elastic supports at the lower end of the fracturing branch pipe can weaken the vibration amplitude, and the optimal scheme can be obtained under the specific working range. The research results can provide theoretical guidance for the vibration characteristics and vibration reduction of fracturing branch pipe.
The pathogenesis of diabetic nephropathy is complex and can ultimately progress to end-stage renal disease, imposing a heavy burden on patients. Current treatment methods show limited efficacy. The protein kinase RNA-like endoplasmic reticulum kinase (PERK)-eukaryotic initiation factor-2$\alpha$(elF2$\alpha$) -activating transcription factor 4 (ATF4)-C/EBP homologous protein (CHOP) signaling pathway serves as a critical pathway in endoplasmic reticulum stress, with downstream regulation of pathological processes such as apoptosis and autophagy closely related to the progression of diabetic nephropathy. Traditional Chinese medicine regulates the PERK-eIF2$\alpha$-ATF4-CHOP pathway through methods that tonify$\mathrm{{Qi}}$and nourish$\mathrm{{Yi}}$, strengthen the spleen and benefit the kidneys, promote diuresis and reduce edema, clear heat and detoxify, as well as invigorate blood and eliminate stasis. These interventions protect the glomerular filtration barrier, reduce capillary basement membrane thickening, enhance protein reabsorption in urine, and delay renal interstitial fibrosis. The mechanistic role of the PERK-eIF2$\alpha$-ATF4-CHOP signaling pathway in diabetic nephropathy was elucidated, the theoretical basis for traditional Chinese medicine interventions in this pathway was summarized, and recent advances were reviewed in the mechanisms of action of effective components of traditional Chinese medicine targeting this pathway, aiming to provide new ideas and methods for the prevention and treatment of diabetic nephropathy through traditional Chinese medicine.
To investigate the deformation mechanism of underground electrical conduits in soft soil considering the softening effect under traffic loads, a USDFLD subroutine was developed based on the dynamic modulus attenuation model. This subroutine was imported into ABAQUS software to establish a three-dimensional finite element model of electrical conduits buried in soft soil foundations. The finite element method was used to analyze the dynamic response of underground electrical conduits under traffic loads. The effects of different traffic load magnitudes (${50}\%$full load,100% full load,200% overload,300% overload) and burial depths (800,850,900,950mm)on the mechanical properties of electrical conduits were studied. The results show that the softening effect of soft soil has a significant impact on the dynamic response of electrical conduits under traffic loads. As the traffic load magnitude increases, the settlement of the electrical conduit gradually increases, and the strain at the bottom of the conduit shifts from symmetric to asymmetric distribution, with an increase in the strain concentration area. Increasing the burial depth of the electrical conduit can significantly reduce the impact of traffic loads on the conduit. When the burial depth increases from${800}\mathrm{\;{mm}}$to${950}\mathrm{\;{mm}}$, the vertical displacement decreases by${39}\%$. The research results provide a scientific basis for the design and construction of power pipes in soft soil areas, and help optimize the depth of pipe embedding and cope with the influence of different traffic loads.
With the depletion of fossil fuels and the emergence of biofuels, ethanol-hydrogen fuel as a new generation of clean renewable fuel has attracted widespread attention. It is necessary to study the effects of ethanol-hydrogen air premixed flame combustion characteristics. Based on the constant volume combustion system, the laminar combustion characteristics of ethanol/hydrogen/air premixed flame were studied under the conditions of initial temperature of${400}\mathrm{\;K}$, hydrogen ratio of${20}\%$, equivalent ratio of${0.7}\sim {1.4}$and initial pressure of$2 \times {10}^{5},3 \times {10}^{5}$and$4 \times {10}^{5}\mathrm{\;{Pa}}$. Based on the mechanism of ethanol oxidation of Marinov and experimental data, the laminar combustion rate of Marinov was studied and the influencing factors were analyzed. Based on Chemkin-Pro software, the chemical reaction kinetics and numerical study were carried out. The results show that the laminar combustion rate of mixed fuel slows down with the increase of pressure.$\mathrm{H}$group is the main pathway of ethanol consumption, and$\mathrm{H},\mathrm{O}$, and$\mathrm{{OH}}$radicals play a leading role in the reaction of${\mathrm{{SC}}}_{2}{\mathrm{H}}_{4}\mathrm{{OH}}$and${\mathrm{{PC}}}_{2}{\mathrm{H}}_{4}\mathrm{{OH}}$from$\mathrm{H}$extracted by ethanol.$\mathrm{R}1 :\mathrm{H}+ {\mathrm{O}}_{2}\rightleftharpoons \mathrm{O}+ \mathrm{{OH}}$has the most positive effect on laminar combustion speed. The peak molar fraction of the active radical pool composed of active free radicals(H, OandOH) has a good correlation with the laminar combustion rate of ethanol in the whole equivalent ratio range, and the influence is huge. Further exploring this correlation, it is found that there is an approximate linear relationship, and the expression of laminar combustion rate with the peak molar fraction of$\mathrm{H}+ \mathrm{{OH}}+{\mathrm{{CH}}}_{3}$and$\mathrm{H}+\mathrm{{OH}}$is fitted.