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ObjectiveThis study aims to deeply investigate the influence of different initial circumferential surface crack shapes (elliptical and sectoral) on pipeline crack propagation behavior under axial forces, thereby providing theoretical support for the structural integrity safety of offshore structures. MethodsThe crack propagation process is simulated and analyzed using the phase field method, and cracks are represented in a diffused manner through a continuous field function. Relying on the Francfort−Marigo variational principle, fracture energy is integrated into the total potential energy of the system. A degradation function is introduced to quantify the reduction of strain energy caused by damage. Secondary development is conducted in finite element software ABAQUS, and the staggered solution strategy is used to solve the problem of pipe crack propagation. ResultsThe results show that when the depth of an elliptical circumferential surface crack is less than half the wall thickness, the crack first propagates circumferentially, then extends through the wall thickness until penetration occurs. When the extent of the elliptical crack penetration is larger, the crack first extends through the wall thickness until penetration, then propagates circumferentially. Sectoral cracks tend to penetrate through the wall thickness first, followed by circumferential expansion. ConclusionsThe results of this study indicate that the fracture phase-field method can accurately simulate the local evolution process of cracks in pipes and highlights the impact of the initial crack shape and the extent of crack penetration on the structural integrity of pipes under the action of axial forces. This has significant implications for enhancing the safety and reliability of pipeline structures.

The Yili Valley, located on the border between China and Kazakhstan, serves as the juncture of North and South Xinjiang, and stands as a pivotal outpost on the Silk Road Economic Belt. This area possesses a fragile ecological environment and experiences frequent debris flow disasters. In this study, four machine learning models:Random Forest (RF), Logistic Regression (LR), Support Vector Machine (SVM), and Decision Tree (DT)-- were employed to evaluate the debris flow susceptibility and compute the weights of evaluation factors. The models were fed inputs comprising 398 identified debris flow channels and 14 feature parameters such as fault density, topographic relief, land use, NDVI, multi-year average rainfall, etc obtained through remote sensing and field surveys. Also, the accuracy of the four machine learning models was evaluated by ROC curves and calculating the Area Under the Curve (AUC). The research results show that: (1) High debris flow susceptibility areas are mainly located in the Tianshan Mountains in the deep river valley region and the loess-covered areas in the mountain front slopes; (2) Multi-year average rainfall, drought index, and topographic relief variability are the top three influential factors controlling the spatial development of debris flows; (3) The AUC values for the validation datasets of the four models were 0.938 (RF), 0.932 (SVM), 0.89 (LR), 0.79 (DT), with the Random Forest model exhibiting superior predictive capability in assessing susceptibility in the region; (4) The disruption of ecological vegetation in the loess-covered region of the study area is a significant cause of frequent debris flow occurrences. Ecological governance and protection efforts should be emplasized to reduce soil erosion and effectively mitigate debris flow disasters at their source.

[Objective] Most conventional straddle monorail track beams utilize a profile form with 850 mm width. In response to the urban rail transit construction demands of the third and fourth-tier cities in China, relevant enterprises propose a profile form with 1 250 mm width for straddle monorail train. To address the special requirements of the new straddle monorail train, it is necessary to study the mechanical performance and profile form of the track beams. [Method] A numerical simulation method is employed to establish a pre-bent steel-concrete composite track beam model. Based on the conventional track beam profile form, a preliminary profile form of 1 250 mm wide pre-bent steel-concrete composite straddle monorail track beam is proposed. The mechanical performance of the profile under different load combinations is analyzed, and the profile parameters of the preliminary profile form are optimized with the goal of minimizing steel consumption. [Result & Conclusion] With the increase of steel box beam top plate thickness, the maximum normal stress of steel box beam upper flange decreases. When the steel box beam bottom plate thickness increases, the maximum normal stress of steel box beam lower flange decreases. With the increase of auxiliary plate thickness, the maximum shear stress of steel box beam auxiliary plate decreases. Under the most unfavorable load working condition combinations, the stiffness and strength of the proposed track beam preliminary profile form both meet the allowable limit of the specifications. The optimized top plate thickness, auxiliary plate thickness, and bottom plate thickness are 16 mm, 20 mm and 16 mm, respectively, contributing to approximately 29.89% reduction in steel surface area.

Studying the tectonic activity characteristics of the Yinchuan basin is of great significance for understanding the interaction among the three major blocks of Qinghai Tibet, Ordos and Alxa. The terrain elevation difference in the Mianzishan-Zhutouling area on the southeastern margin of the Yinchuan basin is significant, and the linear trace on satellite image is obvious, indicating the development of an unknown active fault. This article conducted field geological surveys, trench excavation and stratigraphic dating along the Mianzishan-Qingshuiying line. The results showed that the linear trace along the Mianzishan-Qingshuiying line had been dominated by fault, which was developed on the southeastern margin of the Yinchuan basin with a total length of 50 km. It is divided into two segments, the Mianzishan fault and the Qingshuiying fault. The Mianzishan fault is mainly characterized by high angle normal faults, the scratches on the fault surface show a sinistral strike slip motion, heading northeast, several gullies across the fault layer display left-handed twisting characteristics. The Qingshuiying fault, on the other hand，exhibits a reverse fault trending NEE, developing steep slope landforms. The fault has displaced sedimentary strata deposited at (23.65 ± 1.17) ka BP and (33.16 ± 1.82) ka BP, indicating its latest activity was postdated by Late Pleistocene. The discovery of this fault indicates that the boundary of the northwestern Ordos block is a complex zone associated with a wide structural deformation zone. This zone is not strictly controlled by the boundary faults of Yinchuan basin, but expanded to interior of the Ordos block, which may be related to the continuous northeast pushing and expansion of the Qinghai Tibet Plateau.

[Objective] To adapt to the building characteristics of a new-model straddle monorail train, mechanical performance analysis and interface optimization research are conducted on a new type of PRCTB (pre-stressed reinforced concrete track beam). [Method] A PRCTB suitable for the characteristics of this new-model train is proposed, and an empirically validated numerical analysis model is used to conduct static analysis on eight 25 m-span track beams with different span-height aspect ratios. [Result & Conclusion] The mechanical performance of the proposed new PRCTB meets the regulatory requirements. The 25 m-span new-model track beam exhibits favorable mechanical performance when the span-height aspect ratio ranges from 16∶6 to 18∶5.

ObjectivesThe wetting gradient surface has potential application value in such fields as ship anti-fouling and submarine drag reduction, requiring further research on low-cost and low-complexity wetting gradient surface preparation technology.MethodsThe preparation and static wetting characteristics of a silica-based wetting gradient surface are analyzed using vapor deposition, alkali corrosion and a combination of both.ResultsThe contact angle using vapor deposition reaches 104.9°, with a largest range of about 23°; that using alkali corrosion reaches 80.2°, with a largest range of about 60°; and that using both methods reaches 102.1°, with a largest range of about 40°.ConclusionsThe results of this study can provide references for the preparation of functional surfaces for marine equipment.

To improve the stability and oral absorption effect of salidroside, W/O/W multiple emulsion was prepared with salidroside as the internal aqueous phase and rapeseed oil containing polyglycerol polyricinoleate as the oil phase, and dextran, chitosan and soybean polysaccharide mixed casein as the external aqueous phase. The effects of three polysaccharides with different concentrations on the microstructure, particle size, potential, storage stability, surface hydrophobicity, emulsifying property, embedding rate, drug loading, and in vitro digestion of multiple emulsions were studied. The results showed that compared with the casein control group, chitosan-casein group, and soybean polysaccharide-casein group, dextran-casein W/O/W multiple emulsion had the best stability. A high concentration of dextran could significantly improve the storage stability of dextran-casein multiple emulsions. When the addition of dextran was 1.2%, the average particle size of the multiple emulsions was the smallest, up to 623.03±5.21 nm (P

ObjectiveThis paper aims to explore the hydrodynamic characteristics of underwater vehicles under the action of internal solitary waves.MethodsBased on the internal solitary wave mKdV theory under the strong stratification assumption, the incompressible Navier-Stokes （N-S） equation is discretized by the finite volume method. Combining the velocity entrance wave-making and overset grid methods, a numerical model of an underwater vehicle coupled with internal solitary waves in stratified flow is established. Through this model, the coupling process of internal solitary waves and fixed and suspended vehicles in different internal wave environments is simulated, and the variation law of the hydrodynamic load is obtained by numerical solution. ResultsThe amplitude of the force and moment of the underwater vehicle increases with the increase in wave amplitude. When the position of the fixed vehicle is close to the interface of two layers of fluid, it is more severely affected. When the suspended vehicle is close to the wave trough, the impact is more significant. The increase in the initial pitch angle will lead to a sharp increase in the horizontal force amplitude of the vehicle. In addition, the "falling depth" phenomenon occurs when a vehicle with initial speed is affected by the main wave and coda wave of an internal solitary wave.ConclusionThe results obtained in this paper have reference value for safe operation of underwater vehicles.

Attention deficit hyperactivity disorder (ADHD) is one of the most common mental disorders during childhood, which lasts until adulthood in most cases. In recent years, ADHD classification based on functional magnetic resonance imaging (fMRI) data has become a research hotspot. Most existing classification algorithms reported in the literature assume that samples are balanced; however, ADHD data sets are usually imbalanced. Imbalanced data sets can cause the performance degradation of a classifier by imbalanced learning, which tends to overfocus on the majority class. In this study, we considered an imbalanced neuroimaging classification problem: classification of ADHD using resting state fMRI. We used the functional connection matrix of fMRI as the classification feature and proposed a multi-objective data classification scheme based on a support vector machine (SVM) to aid the diagnosis of ADHD. In this scheme, the imbalanced data classification problem is formulated as an SVM model with three objectives: maximizing the margin, minimizing the sum of positive errors, and minimizing the sum of negative errors. Accordingly, the positive and negative sample empirical errors can be separately handled. Then, the model is solved by a multi-objective optimization method, i.e., normal boundary intersection method. A set of representative classifiers are computed for selection by decision makers. The proposed scheme was tested and evaluated on five data sets from the ADHD-200 consortium and compared with traditional classification methods. Experimental results show that the proposed three-objective SVM classification scheme is better than traditional classification methods reported in the literature. It can effectively address the data imbalance problem from the algorithm level. This scheme can be used in the diagnosis of ADHD as well as other diseases, such as Alzheimer’s and Autism.

In order to identify the faults of rolling bearing of wind turbines, the variational modal decomposition (VMD) was combined with two methods, including calculation order tracking (COT) and reversed sequence squared envelope spectrum (RE-SES), to carry out the envelope order analysis. The non-stationary signals in time domain were converted into stationary signals in angle domain by equal angle sampling. And the bearing fault characteristic information was obtained by envelope method. The results show that the modulation order of amplitude modulation signal can be extracted more effectively by VMD combined with RE-SES envelope order method. The VMD filter could make the fault feature order more prominent, and it is easy to identify the fault, and it provide reference for the fault diagnosis of rolling bearing of wind turbine under variable speed condition.

cDNA microarray technique was used to study the mechanisms of liver injury caused by Huangyaozi at level of gene expression based on the biological functions of those differentially expressed genes. For the mice taking Huangyaozi for 15 days,there were 83 differentially expressed genes,among them 18 genes were up-regulated and 65 genes were downregulated, and the increase of serum ALT,AST and tissue total protein were notable. For the mice taking Huangyaozi for 30 days, there were 1658 differentially expressed genes,among them 917 genes were up-regulated and 741 genes were down-regulated. And the liver index, serum ALT and tissue total protein were all increased significantly but AST,AKP decreased significantly. There were 45 common differentially expressed genes in the two groups,among them 9 genes were upregulated,while the other 36 genes were down-regulated. According to the differentially expressed genes with different duration for taking Huangyaozi, the phased change about occurrence and development of liver injury was analyzed. The results indicated that the gene expression profile of mouse liver cell could be changed significantly by taking Huangyaozi, which might be important for elucidating the mechanisms of liver injury caused by Huangyaozi.