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Limited by mining technology, mineral exploitation can produce large amounts of tailings. Heavy summer rainfall or seasonal freeze-thaw can lead to physical and chemical modification of tailing material in mountainous areas, resulting in fluidized tailings flow and severe disaster losses. Therefore, aiming at the problem of tailings fluidization catastrophe, this paper tried to reveal the rheological mechanism of tailings fluidization transformation by combining rheological tests and theoretical analysis. The results show that the yield stress increases with decreasing temperature, and when the density of debris flow (ρ) is more than 1.9 g/cm3, this behavior becomes more pronounced as the density increases. The storage modulus decreases by at least two orders of magnitude at the solid-fluid transition under amplitude test sweep. Storage and loss modulus in the linear viscoelastic range and yield stress have an exponential growth relationship with sediment concentration. In addition, a stress constitutive relation and a new exponential law describing the evolution of yield stress required for solid-liquid transformation were proposed, and the relationship is further strengthened through a comprehensive analysis of existing results, which expands the evaluation application of the rheological characteristics of tailings flow. This paper provides a new insight into the rheological properties of tailing and how they occur through solid-liquid transition under different environments, which is beneficial to geological hazard prevention and the ecological remediation of the mining area. [ABSTRACT FROM AUTHOR]

The currently available heat-sink materials cannot meet the requirements for the 5G and beyond technology. Copper (Cu)/diamond composites have been proposed because Cu and diamond are excellent thermal conductors, while diamond has a very low coefficient of thermal expansion. Mixing Cu and diamond to form a composite seems a straightforward approach. However, this simple approach has never succeeded because, chemically, Cu does not wet diamond. Therefore the Cu-diamond interface cannot be tightly bonded, leading to an inferior thermal conductivity. This study presents a modified press and sinter process for depositing Cu submicronic particles onto diamond reinforcements prior to densification by hot pressing. The initial results obtained from microstructural observations and x-ray photoelectron spectroscopy have shown that our strategy can lead to successful Cu deposition onto diamond particles. The Cu deposition leads to a well-bonded interface between the copper matrix and diamond reinforcement, ultimately resulting in excellent thermal conductivity. [ABSTRACT FROM AUTHOR]

Whereas loess-mudstone landslides are widely distributed and frequently occurred at the loess Plateau, this type of landslides is hard to detect due to its particularity, and easily generates serious losses. To clarify the shear characteristics and formation mechanism of loess-mudstone landslides, field investigations, ring shear tests and numerical simulation analyses were performed on the loess specimens collected from the Dingjiagou landslide in Yan'an city, China. The test results showed that both the peak strength and residual strength of slip zone soils have a decreasing tendency with moisture content, while the increasing of normal stress caused an increase in the shear strength. These phenomena indicate that the rise in the moisture content induced by precipitation or the decreasing of normal stress due to excavation activities would result in the weakening of slip zone soils. Numerical simulations of the evolution process of slope failure using the finite element method were conducted based on the Mohr-Coulomb criterion. It was found that the heavy precipitation played a more important role in the slope instability compared with the excavation. In addition, the field investigation showed that loess soils with well-developed cracks and underlying mudstone soils provide material base for the formation of loess-mudstone landslides. Finally, the formation mechanism of this type of landslides was divided into three stages, namely, the local deformation stage, the penetration stage, the creeping — sliding stage. This study may provide a basis for understanding the sliding process of loess-mudstone landslides, as well as guidelines for the prevention and mitigation of loess-mudstone landslides. [ABSTRACT FROM AUTHOR]

Rock creep properties can be used to predict the long-term stability in rock engineering. In reservoir bank slopes, sandstones which are frequently used in the bank slope undergoing long-term effects of dry-wet (DW) cycles due to periodic water inundation and drainage may gradually accumulate creep deformation, resulting in rock structure's damage or even geological hazards such as landslides. To fully investigate the effect of DW cycles on the creep damage properties of sandstone, triaxial creep tests were conducted on saturated sandstone with different DW cycles by using a triaxial rheometer apparatus. The experimental results show that both the instantaneous strain and the stabilized strain increase with the DW cycles. In addition, using the Burgers model, four kinds of functions including an exponentially decreasing function, a linearly decreasing function, a linearly increasing function and an exponentially increasing function were proposed to express the relationships between the shear modulus, viscoelastic parameters of the Burgers model and the deviatoric stress under different DW cycles. Through comparative analysis, it is found that the theoretical curves generated using proposed four kinds of functions are in good agreement with the experimental data. Furthermore, macromorphological and microstructural observations were performed on specimens after various triaxial rheological tests. For samples with small number of DW cycles, approximately X-shaped fracture surfaces were observed in shear failure zones, whereas several shear fractures including obvious axial and horizontal tensile cracks, and flaws were found for samples with relatively large DW cycles due to long-term propagation and evolution of micro-fissures and micro-pores. Furthermore, as the DW cycles increases, the variation in micro-structure of samples after creep failure was summarized into three stages, namely, a stage with good and dense structure, a stage with pore and fissure propagation, and a stage with extensive increase of pores, fissures and loose particles. It is concluded that the combination effect of permeation of water molecules through pores and fissures within sandstone, and the propagation of preexisting pores and fissures owing to the dissolution of mineral particles leads to further deterioration of the mechanical properties of sandstone as the number of DW cycles increases. This study provides a fundamental basis for evaluating the long-term stability of reservoir bank slopes under cyclic fluctuations of water level. [ABSTRACT FROM AUTHOR]

It is well known that the hydromechanical behavior of both saturated and unsaturated loess soils is significantly influenced by the soil fabric. However, there is limited understanding of how the soil fabric or structure evolves due to mechanical, hydraulic and chemical changes on loess soils. Information of the microstructural evolution or change in pore-size distribution (i.e., PSD) of loess soils along different stress paths is valuable for proposing an advanced constitutive model that considers the microstructure and can better model the hydromechanical behavior of loess soils. For this reason, in the present study, the microstructure is characterized on intact and saturated loess specimens before and after oedometer consolidation tests, using scanning electron microscopy and mercury intrusion porosimetry methods. The results suggest that the loading-induced change in PSD varies with stress level and saturation state of the loess soil. A reduction arises in the cumulative intrusion void ratio due to an increase in vertical stress, which accounts for compression of inter-aggregate pores greater than 6 μm. However, loading saturated loess leads to transformation from a bimodal PSD into a trimodal one that defines three major pore series, namely large-pore series (i.e., more than 6 μm), medium-pore series (i.e., between 0.1 and 6 μm) and small-pore series (i.e., less than 0.1 μm). The trimodal nature of PSD is, however, destructed under higher vertical stresses. Both large pores and medium pores are compressed under higher vertical stresses (i.e., > 600 kPa). The inundating-induced change in PSD is dependent on loading condition and can be discerned to take place in the same three pore series. Not only large pores but also medium pores collapse upon inundating under higher vertical stresses (i.e., > 600 kPa). The microstructural evolution is consistent with the mechanical responses of both intact and saturated loess. [ABSTRACT FROM AUTHOR]

Since it is difficult to obtain a large number of failure data in a short time, performance degradation analysis is a reliability analysis method which can effectively compensate for the lack of data. Linear degradation process is used to describe the performance degradation process of mechanical systems. Considering the extreme impact and operation impact of products, the threshold effect of performance degradation process on sudden failure is analyzed. Based on the performance degradation process of variable failure threshold and the impact process of variable failure threshold, a competitive failure reliability model with both sudden failure and performance degradation failure is established. The reliability model is analyzed with an example. The results show that the reliability of the product is overestimated if the invalidation threshold is fixed and the change of the invalidation threshold is neglected. [ABSTRACT FROM AUTHOR]

After water is impounded in a reservoir, rock mass in the hydro-fluctuation belt of the reservoir bank slope is subject to water saturationdehydration circulation (WSDC). To quantify the rate of change of rock mechanical properties, samples from the Longtan dam area were measured with uniaxial compression tests after different numbers (1, 5, 10, 15, and 20) of simulated WSDC cycles. Based on the curves derived from these tests, a modified Hoek- Brown failure criterion was proposed, in which a new parameter was introduced to model the cumulative damage to rocks after WSDC. A case of an engineering application was analyzed, and the results showed that the modified Hoek-Brown failure criterion is useful. Under similar WSDC-influenced engineering and geological conditions, rock mass strength parameters required for analysis and evaluation of rock slope stability can be estimated according to this modified Hoek-Brown failure criterion. [ABSTRACT FROM AUTHOR]

To investigate the formation mechanism and the stability of Wanjia middle school slope in Wenchuan Earthquake Area, the macroscopic geological characteristics and the failure process of the landslide are researched by engineering geology analysis method, limit equilibrium method, and finit element method. The results show that after the Wenchuan Earthquake, retaining walls, houses and other infrastructure on the foot of Wanjia middle school slope were severely destroyed, 10 cm wide tension fracture appeared at the trailing edge of the slope. Wanjia middle school slope is a type of medium-sized soil landslide. The area of the deformation body is about 19,314 m, the total volume of the deformation body is about 23 × 10 m. There may be two potential sliding surfaces in the unstable slope: shallow and deep landslide. The analysis results of the limit equilibrium method and the finite element method show that: under dead weight, dead weight + rainstorm, dead weight + earthquake conditions, the plastic zone occurs mainly at the middle part or the trailing edge of the slope, and it doesn't fully cut through the deep landslide body, so the deep landslide is stable. However, under rainstorm or earthquake conditions, the plastic zone almost completely cut thorough the shallow landslide body, it shows that the shallow landslide is in the understable-basic stable state. It is found that the results of finite element method is concordant with the results of the limit equilibrium method ( F = 1.06-1.29, the shallow landslide is in the basic stable-stable state). The calculation results show that shallow landslides are likely to occur in Wanjia middle school slope during a rainstorm or an earthquake, so monitoring and control of the slope should be strengthened. The shallow landslide should be managed by some measures, such as anti slide pile retaining structures and drainage works, and the dangerous rock bodies on the slope surface should be cleaned up. [ABSTRACT FROM AUTHOR]

Restoring soil quality is the main evaluation norm of the reclamation. In order to reveal the effects of mushroom waste on the quality improvement of reclaimed soil in coal mining areas, the physical, chemical and microbial characteristics of soil are studied. The results show clear improvement in the soil after using mushroom waste. Because of human cultivation and fertilization, cultivated soil after reclamation exhibits high comprehensive quality and the index of quality of surface soil reaches 0.64 and 0.73. The average index of surface soil quality is as high as 0.52 and 0.54. In comparison, the quality of reclaimed soil of forest land is low, with average index of 0.40. The effects of mushroom waste are mainly on the surface soil in the first 2 years after the application. After that period, with the decomposition of mushroom waste, soil quality index tends to be the same as the original soil. The quality of surface soil is higher than that of subsoil, especially after the application of mushroom waste, at which point the soil quality reaches a peak at about 15 cm. Cultivated soil after reclamation has great variance in quality, after the coefficient of 24.74%. Mushroom waste can reduce such variation, particularly with long-term use. The variance efficient falls to 3.59% after 3-year application. [ABSTRACT FROM AUTHOR]

Objective: To investigate the relationship between renal function and clinical outcomes among patients with acute ST-segment elevation myocardial infarction (ASTEMI), who were treated with emergency percutaneous coronary intervention (PCI). Methods: 420 patients hospitalized in Peking University First Hospital, diagnosed with ASTEMI treated with emergency (PCI) from January 2001 to June 2011 were enrolled in this study. Estimated glomerular filtration rate (eGFR) was used as a measure of renal function. We compared the clinical parameters and outcomes between ASTEMI patients combined renal insufficiency and the patients with normal renal function. Results: There was a significant increase in the concentrations of fibrinogen and D-Dimer ( P<0.05) and a much higher morbidity of diabetes mellitus in the group of patients with chronic kidney disease (CKD; eGFR<60 ml/(min·1.73 m)) ( P<0.01). CKD (eGFR<60 ml/(min·1.73 m)) was an independent predictor of in-hospital mortality for patients hospitalized with ASTEMI receiving PCI therapy rapidly ( P=0.032, odds ratio (OR) 4.159, 95% confidence interval (CI) 1.127-15.346). Conclusions: Renal insufficiency is an independent predictor of in-hospital mortality for patients hospitalized with ASTEMI treated with primary PCI. [ABSTRACT FROM AUTHOR]

Based on the random perturbation technique for reliability sensitivity design, some realistic reliability-based sensitivity issues are discussed, some of which have a structure of high nonlinear performance functions. Combining the related theories of the moment method of the reliability analysis, the matrix differential, and the Kronecker algebra, the reliability-based sensitivity method based on the perturbation method is modified if the first four moments of random variables are given. Meanwhile, a reliability-based sensitivity computation method is proposed. Some examples are used to show that using this method can effectively improve the accuracy of the reliability-based sensitivity computation and offer a reliable theoretic basis in engineering. [ABSTRACT FROM AUTHOR]

We study dynamical behaviors in coupled nonlinear oscillators and find that under certain conditions, a whole coupled oscillator system can cease oscillation and transfer to a globally nonuniform stationary state [i.e., the so-called oscillation death (OD) state], and this phenomenon can be generally observed. This OD state depends on coupling strengths and is clearly different from previously studied amplitude death (AD) state, which refers to the phenomenon where the whole system is trapped into homogeneously steady state of a fixed point, which already exists but is unstable in the absence of coupling. For larger systems, very rich pattern structures of global death states are observed. These Turing-like patterns may share some essential features with the classical Turing pattern. [ABSTRACT FROM AUTHOR]

By a small-size complex network of coupled chaotic Hindmarsh-Rose circuits, we study experimentally the stability of network synchronization to the removal of shortcut links. It is shown that the removal of a single shortcut link may destroy either completely or partially the network synchronization. Interestingly, when the network is partially desynchronized, it is found that the oscillators can be organized into different groups, with oscillators within each group being highly synchronized but are not for oscillators from different groups, showing the intriguing phenomenon of cluster synchronization. The experimental results are analyzed by the method of eigenvalue analysis, which implies that the formation of cluster synchronization is crucially dependent on the network symmetries. Our study demonstrates the observability of cluster synchronization in realistic systems, and indicates the feasibility of controlling network synchronization by adjusting network topology. [ABSTRACT FROM AUTHOR]