With the rapid development of social economy, the deterioration of environment has become more and more serious; it is urgent to find a balance between economic development and environmental ...protection. Therefore, enterprises are appealed to invest in environmental protection, and local municipalities are appealed to supervise the environmental behaviors of enterprises, while central government plays a role of regulation. In order to study the preconditions for a better environmental strategy combination of local municipalities and enterprises, an evolutionary game theory was first constructed in this paper, then the evolutionary stable strategy (ESS) of local municipalities and enterprises under different scenarios was examined, and finally a simulation was used to test the results of the analysis. The results indicate that central government’s regulation has influence on the strategies chosen by local municipalities and enterprises, the larger the degree of central government’s incentives are, the more possible local municipalities and enterprises would choose environment-friendly strategies; and the intensity of central government's regulation, the cost and benefits of local municipalities’ supervision, and the cost and benefits of enterprises' environmental investment are the key influence factors.
Graphene quantum dots (GQDs) have attracted tremendous research interest due to the unique properties associated with both graphene and quantum dots. Here, a new application of GQDs as ideal ...electrode materials for supercapacitors is reported. To this end, a GQDs//GQDs symmetric micro‐supercapacitor is prepared using a simple electro‐deposition approach, and its electrochemical properties in aqueous electrolyte and ionic liquid electrolyte are systematically investigated. The results show that the as‐made GQDs micro‐supercapacitor has superior rate capability up to 1000 V s−1, excellent power response with very short relaxation time constant (τ0 = 103.6 μs in aqueous electrolyte and τ0 = 53.8 μs in ionic liquid electrolyte), and excellent cycle stability. Additionally, another GQDs//MnO2 asymmetric supercapacitor is also built using MnO2 nanoneedles as the positive electrode and GQDs as the negative electrode in aqueous electrolyte. Its specific capacitance and energy density are both two times higher than those of GQDs//GQDs symmetric micro‐supercapacitor in the same electrolyte. The results presented here may pave the way for a new promising application of GQDs in micropower suppliers and microenergy storage devices.
Graphene quantum dots (GQDs)‐based micro‐supercapacitors are prepared using a simple eletrodeposition approach and their electrochemical properties in aqueous and ionic liquid electrolytes are studied. The GQDs‐based micro‐supercapacitors exhibit superior rate capability, high power response capability, and excellent cyclic stability
Lipid nanovesicles, including endogenous exosomes and synthetic lipid nanoparticles, have shown great potential in disease diagnostics, drug delivery, and cancer biology. Naturally secreted ...nanovesicles are promising biomarkers for early detection of cancers in vitro. Synthetic nanovesicles serve as robust drug delivery systems with enhanced tumor targeting in vivo. Microfluidic platforms with features of excellent flow control and rapid mixing are exploited as versatile tools for studying lipid nanovesicles of small sizes and delicate structures. Here, an overview of microfluidics for precise manipulation and synthesis of lipid nanovesicles is provided. The mechanisms of isolation and detection of exosomes in microfluidics, as well as the clinical utility of exosomes for cancer diagnosis, are discussed. Several microfluidic designs for controlled assembly of a variety of lipid nanovesicles are highlighted. Opportunities and outstanding challenges of microfluidics‐based investigation of lipid nanovesicles are discussed.
Lipid nanovesicles, including endogenous exosomes and synthetic lipid nanoparticles, have shown great potential in disease diagnostics, drug delivery, and cancer biology. An overview of recent advances of microfluidic methods for precise manipulation and synthesis of lipid nanovesicles is provided. A discussion on the clinical opportunities and challenges of lipid‐nanovesicles‐based cancer diagnostics and therapy by microfluidics is presented.
A series of true-triaxial compression tests were performed on red sandstone cubic specimens with a circular hole to investigate the influence of depth on induced spalling in tunnels. The failure ...process of the hole sidewalls was monitored and recorded in real-time by a micro-video monitoring equipment. The general failure evolution processes of the hole sidewall at different initial depths (500 m, 1000 m and 1500 m) during the adjustment of vertical stress were obtained. The results show that the hole sidewall all formed spalling before resulting in strain rockburst, and ultimately forming a V-shaped notch. The far-field principal stress for the initial failure of the tunnel shows a good positive linear correlation with the depth. As the depth increases, the stress required for the initial failure of the tunnels clearly increased, the spalling became more intense; the size and mass of the rock fragments and depth and width of the V-shaped notches increased, and the range of the failure zone extends along the hole sidewall from the local area to the entire area. Therefore, as the depth increases, the support area around the tunnel should be increased accordingly to prevent spalling.
To review the rockburst proneness (or tendency) criteria of rock materials and compare the judgment accuracy of them, twenty criteria were summarized, and their judgment accuracy was evaluated and ...compared based on the laboratory tests on fourteen types of rocks. This study begins firstly by introducing the twenty rockburst proneness criteria, and their origins, definitions, calculation methods and grading standards were summarized in detail. Subsequently, to evaluate and compare the judgment accuracy of the twenty criteria, a series of laboratory tests were carried out on fourteen types of rocks, and the rockburst proneness judgment results of the twenty criteria for the fourteen types of rocks were obtained accordingly. Moreover, to provide a unified basis for the judgment accuracy evaluation of above criteria, a classification standard (obtained according to the actual failure results and phenomena of rock specimen) of rockburst proneness in laboratory tests was introduced. The judgment results of the twenty criteria were compared with the judgment results of this classification standard. The results show that the judgment results of the criterion based on residual elastic energy (REE) index are completely consistent with the actual rockburst proneness, and the other criteria have some inconsistent situations more or less. Moreover, the REE index is based on the linear energy storage law and defined in form of a difference value and considered the whole failure process, and these superior characteristics ensure its accuracy. It is believed that the criterion based on REE index is comparatively more accurate and scientific than other criteria, and it can be recommended to be applied to judge the rockburst proneness of rock materials.
A considerable number of deep engineering cases show that strain rockbursts occur on both sidewalls of circular caverns and ultimately form a symmetrical V-shaped notch. To investigate the occurrence ...process and mechanism of strain rockbursts in deep circular cavern under high stresses, simulation experiments under four different three-dimensional (3D) stress conditions were conducted on cubic granite specimens with a prefabricated circular hole using the true-triaxial electro-hydraulic servo mutagenesis testing system. The rock bursting process was monitored on the sidewalls of the hole and recorded in real-time with a wireless microcamera. The results show that the entire rock bursting process on the sidewalls can be divided into four distinct periods for every 3D stress condition: calm period, pellet ejection period, rock fragment exfoliation period, and rock bursting period. Under the conditions that the vertical stress is constant and the horizontal radial stress is equal to the horizontal axial stress, the rockburst severity of the sidewalls clearly decreases with increasing horizontal stress. When the vertical stress is constant and the horizontal axial stress is low, the rockburst severity clearly decreases with the increase of horizontal radial stress. In contrast, when the horizontal axial stress is high, the rockburst severity becomes more serious with increasing horizontal radial stress. During the process of rock fracture and bursting, the damage zones on both sidewalls form two symmetrical V-shaped notches, and the line connecting the centres of the two V-shaped notches is perpendicular to the maximum principal stress direction. The symmetrical V-shaped failure modes on both sidewalls under the four stress conditions are in line with the statistical relationship of the far-field stress state and failure mode of a deep circular cavern without support (Martin et al. in Can Geotech J 36(1):136–151, 1999).
To study the energy storage and dissipation characteristics of deep rock under two-dimensional compression with constant confining pressure, the single cyclic loading-unloading two-dimensional ...compression tests were performed on granite specimens with two height-to-width (
H/W
) ratios under five confining pressures. Three energy density parameters (input energy density, elastic energy density and dissipated energy density) in the axial and lateral directions of granite specimens under different confining pressures were calculated using the area integral method. The experimental results show that, for the specimens with a specific
H/W
ratio, these three energy density parameters in the axial and lateral directions increase nonlinearly with the confining pressure as quadratic polynomial functions. Under constant confining pressure compression, the linear energy storage law of granite specimens in the axial and lateral directions was founded. Using the linear energy storage law in different directions, the elastic energy density in various directions (axial elastic energy density, lateral elastic energy density and total elastic energy density) of granite under any specific confining pressures can be calculated. When the
H/W
ratio varies from 1:1 to 2:1, the lateral compression energy storage coefficient increases and the corresponding axial compression energy storage coefficient decreases, while the total compression energy storage coefficient is almost independent of the
H/W
ratio.
With the rapid development of social economy and the increasing environmental pollution in China, the government’s environmental investment has been gradually increasing, and an effective evaluation ...system is required to study the benefits from environmental investment. Based on the literature review and current situation analysis of the benefits from environmental investment, the selection of indicators was determined after the analysis of the economic, environmental, and social benefits of environmental investment. The gray relation analysis (GRA) method was adopted to test the correlation between each indicator and environmental investment, the combination of analytic hierarchy process (AHP) and Delphi method was used to determine the relative weight of each indicator, and a fuzzy comprehensive evaluation model was established for benefits from environmental investment. The study found that benefits from environmental investment in China had been improving over years but still not satisfying, and several suggestions had been proposed according to the analysis.
The effects of high strain rates and low confining pressures on the dynamic mechanical properties of sandstone were investigated experimentally with a modified triaxial split Hopkinson pressure bar ...(SHPB) system. For comparison, dynamic uniaxial compression tests of the sandstone were also conducted by using a conventional SHPB system. The confining pressures used in the dynamic triaxial compression tests are 5, 7.5, 10, 12.5 and 15 MPa, and the strain rate of these tests varied from approximately 40 s−1 to 160 s−1. The results show that the dynamic uniaxial and triaxial compressive strengths of the sandstone will linearly increase with the logarithm of the stain rate. Under approximately the same strain rate, the dynamic triaxial compressive strength will linearly increase with the confining pressure. Although the peak strain has no dependence on the confining pressure, it will generally increase with the strain rate. The secant modulus is independent of the strain rate and confining pressure. Three trend diagrams, which reflect the influences of strain rate or confining pressure on the dynamic mechanical properties of sandstone in the uniaxial and triaxial compression tests, are given, and the correlation between the failure modes of the sandstone specimens and the characteristics of the stress-strain curves is also analyzed.
To evaluate the deterioration degree of rock freeze–thaw damage in cold area engineering, it is necessary to establish an accurate freeze–thaw rock damage model and its uniaxial compression numerical ...simulation method. Therefore, indoor freeze–thaw cycle tests of saturated yellow sandstone were carried out. The porosity and P-wave velocity were measured, and uniaxial compression tests were conducted after different numbers of freeze–thaw cycles. The findings indicate that with an increasing number of freeze–thaw cycles, the elastic modulus, peak strength and wave velocity of the yellow sandstones gradually decrease, while the peak strain and the average porosity increase. The energy evolution law with different numbers of freeze–thaw cycles was analyzed, a freeze–thaw damage model was established according to the relative change in the dissipated energy ratio before and after freezing–thawing, and the accuracy of this damage model and five common damage models was evaluated by the uniaxial compressive strength and peak strain. The functional relationship between mesoscopic parameters and the number of freeze–thaw cycles was formulated to establish a numerical simulation method for saturated sandstones under uniaxial compression after freeze–thaw cycling. The reliability of the numerical method was verified by comparing the stress–strain curve, peak stress, peak strain and energy law with the experimental results.
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