Search

In order to obtain the creep characteristics of the surrounding rock of the Dianzhong water diversion tunnel and to study the long-term stability of the surrounding rock of the tunnel, a fully automated triaxial developed by Wuhan Institute of Geotechnics, Chinese Academy of Sciences, is used to carry out the uniaxial creep test of green mud shale. The axial creep curve and isochronous stress-strain curve of green mud shale are obtained. And the long-term strength value of green mud shale is determined based on the characteristics of isochronous stress-strain curve. Based on the classical creep curve characteristics and a large number of experimental creep curves, it is found that the equations describing the attenuation creep curve can be treated by symmetry. Therefore, it is assumed that the acceleration curve and the decay creep curve are symmetric about the midpoint of the stable creep curve. An accelerated creep model based on the symmetry of the creep curve is obtained. And a set of methods to determine the parameters of the creep model is proposed based on the characteristics of the creep test curve. Finally, the parameters introduced into the accelerated creep model for sensitivity analysis. The parameters introduced into the model have a clear physical meaning. The results show that with the increasing axial stress, the instantaneous strain value and creep deformation value of the rock are also increasing, and the instantaneous strain of the rock under the first stage load accounts for the largest ratio of the total creep deformation. The established creep model can not only well describe the attenuation creep and stable creep deformation law of green mud shale, it also better make up for the defects of the Nishihara model that cannot describe the accelerated creep. The agreement between the model curve and the test curve is much higher than that between the model and the test curve, and the correlation coefficients between the model curve and the test curve under different stresses are all above 0.90. Meanwhile, the validation of different types of test curves and model curves also shows that the model can be applied to the prediction of creep curves of different types of rocks. Finally, the value of parameter j is introduced to control the deformation rate and the time to enter accelerated creep. The value of parameter k controls the creep time and the creep rate in the accelerated stage.

To improve the gel quality of chicken blood, a by-product of concentrated slaughter, the effects of different concentrations and formulations of xanthan gum (XG) and guar gum (GG) on the gel properties of chicken blood were investigated using the indices of water retention, texture, and rheological properties, as well as analysis of molecular interactions and sensory scores. The results showed that while individual treatment with either XG or GG improved the water-holding capacity of the chicken blood gel, the action of XG was superior. Addition of 4.0 g/L of XG resulted in a cooking loss rate of 10.02%, centrifugation loss of 12.73%, and syneresis rate of 10.96% (at 48 h), while the hardness, cohesiveness, gelation, mastication, and recovery of the gel were decreased. Addition of 6.0 g/L of GG significantly improved the textural properties of the gel, resulting in a hardness of 366.95 N, elasticity of 0.94 mm, cohesiveness of 0.77, adhesiveness of 281.94, masticatory value of 263.72 mJ, and recovery of 0.25. Analysis of dynamic rheology and intermolecular forces showed that the gelation transformation of the chicken blood gel system was mainly determined by the elastic response. The formulation of XG and GG had a synergistic effect in stabilizing the chicken blood gel, with strengthened ionic bonds (from 29.18% to 32.62%) and hydrogen bonds (from 2.48% to 6.43%), reduced hydrophobic force (from 22.68% to 16.28%), increased water-holding capacity of the gel, and enhanced gel stability. The addition of 4.0 g/L of formulated colloid (XG and GG in a ratio of 7:3) to chicken blood resulted in optimal water retention and texture, together with high sensory scores of the gel.

In order to truly reveal the mechanism of rock deformation and failure and the nature of rock material damage, based on the analysis of rock material deformation law and mechanical characteristics, a rock damage constitutive model based on elastic energy release rate is established using the energy principle. Taking the damage variable as an internal variable that affected the change of rock performance, a new type of statistical damage constitutive model for rock is established based on the effective stress principle and statistical damage theory. It further improves the theoretical system of rock damage constitutive model and mades up for the shortcomings that traditional damage models cannot reasonably explain the causes of rock failure. The parameters of the damage model are determined using the rock test data, and the feasibility and applicability of the damage model are verified through a comparative analysis of the model curve and the test curve. The damage evolution model is substituted into the elastic energy-strain model to analyze the law of rock elastic energy change during loading. The results show that the model curve and the test curve almost coincide in the deformation phase before the peak, indicating that the damage model perfectly reflects the linear elastic deformation characteristics of the rock. The model curve and the test curve do not agree well at the post-peak stage, but they also have a good description of the nonlinear deformation law of the rock. The damage model also better reflectes the relationship between the accumulation and release of elastic energy and the damage and destruction of rocks, and the characteristics of the degree of rock damage increases with the increasing confining pressure. At the same time, in the initial loading stage, the damage variable of the rock increases with the increasing axial strain. This shows that under the load, the internal cracks in the rock gradually develop, so that the damage of the rock material is gradually accumulated. When the confining pressure reaches above 10 MPa, the damage-strain curves basically coincide. The growth rate of the damage-strain curve rises sharply at the moment of initial loading. When the strain of the rock is about 0.01%, the damage-strain curve changes from rapid growth to steady growth. Because the damage quickly accumulates near the peak stress point of the rock, the damage variable rapidly increases to 1 in value.

Hetao Plain is one of the most serious area of local arsenic poisoning in China.Based on shallow groundwater arsenic samples, the paper used the semivariogram to reveal the spatial distribution and heterogeneity of groundwater arsenic concentration, and further discussed the influencing factors.The results show that the arsenic concentration in groundwater generally increases from south to north in the Hetao Plain.The residual groundwater arsenic concentration is fitted to the pure nugget effect model under the assumption of isotropic conditions, which means it is random on the measured scale, so there is no spatial autocorrelation and the variance is great in short distances.The fractal dimension value is large(D=1.999), further indicating the distinct variation of groundwater arsenic concentration within the measured scale.Groundwater arsenic is closely related to organic matters in sediments.Since the Late Quaternary, the tectonic movements of the northern mountains and changes in the sedimentary environment of the basin has caused multiple sedimentary facies, resulting in a high degree of spatial variability in burial conditions of organic matters.The high spatial variability of organic matters characteristics further leads to high spatial variability of groundwater arsenic concentration.The slow groundwater flow plays an important role in maintaining this pattern.This article focuses on the spatial heterogeneity of groundwater arsenic in the Hetao area, which has scientific significance for effectively predicting the potential risk of arsenic exposure in drinking water in unknown areas, accurately preventing endemic diseases and ensuring water supply safety.

In order to solve the background clutter interference, occlusion and other practical problems faced by infrared imaging guided missile in the process of tracking aerial small target, an improved algorithm based on fully-convolutional Siamese networks is proposed. This algorithm judges target tracking state by the average peak to correlation energy and the maximum peak of deep feature response map. When target is jammed by background clutter, the deep feature response value combined with the local contrast between target and clutter is used to select target. When target is judged to be obscured, the target position is predicted by Kalman filter. Compared with the benchmark algorithm SiamFC, the tracking success rate and accuracy of the improved algorithm are improved by 33.4% and 21.9% respectively, when tested on the infrared aerial dim small target dataset. Experimental results show that the proposed algorithm can adapt to complex and diverse infrared aerial scenes, and realize effective and stable real-time tracking for infrared aerial small target.

Objective: The effect of sandblasting on the bond strength between 3mol% yttrium-stabilized tetragonal zirconium polycrystal (3Y-TZP) zirconia framework and veneering porcelain was evaluated., Methods: A total of 21 specimens [(25 ± 1) mm x (3 ± 0.1) mmx (0.5 ± 0.05) mm] were prepared according to ISO 9693. The specimens were then randomly divided into 3 groups. Sandblasting was performed on 2 meshes of Al₂O₃ particles: group A with mesh 110 and group B with mesh 80. Group C, which was not sandblasted, was the control group. The surface roughness of the zirconia framework, as well as the bond strength between 3Y-TZP zirconia framework and veneering porcelain, was measured. The interface microstructure was observed by scanning electron microscope (SEM), and elemental distribution was detected by energy dispersive spectroscopy (EDS)., Results: Surface roughness values were (1.272 ± 0.149) μm for group A, (0.622 ± 0.113) μm for group B, and (0.221 ± 0.065) μm for group C. Statistical significance were found among groups (P < 0.05). The bond strength values were (28.21 ± 1.52) MPa for group A, (27.71 ± 1.27) MPa for group B, and (24.87 ± 3.84) MPa for group C. Statistical significance was found between group A and group C (P < 0.05), whereas the other groups had no statistical significance (P > 0.05). Interface adhesion failure was the primary performance. SEM images showed the close interface bonding, and EDS showed that the interface had no obvious element penetration., Conclusion: Al₂O₃ sandblasting can slightly enhance the bond strength between zirconia framework and veneering porcelain.