A Numerical Research on Crack Process of Gypsum Containing Single Flaw with Different Angle and Length in Uniaxial Loading

To investigate the crack behaviour of rock or rock-like material in uniaxial loading, a series of numerical simulations were conducted on gypsum specimens containing a single flaw with different inclination angle (0°–90°) and length (10 mm–30 mm). Based on the numerical simulations results, the effect of flaw length on peak strength, the CI stress, and the CD stress were investigated with different inclination angles. The results show that the peak strength decreased initially and then increased with increasing of the flaw angle. Meanwhile, the peak strength decreased gradually when the length of the preexisting flaw increased. When the inclination angle was 30°, 45°, and 60°, the reduction degree of peak strength increased with increasing of the flaw length. The CI stress and CD stress not only depend on the inclination angle but also depend on flaw length. Four types of crack were observed in numerical simulations. The present research facilitates increased understanding of crack behaviour of rock under different conditions

Experimental study on microbial mineralization for removing contaminants from groundwater in mining areas of in-situ uranium leaching

BackgroundThe remediation technology for U(VI), Ca2+ and other pollutants in the groundwater of the mining area of in-situ leaching of uranium has become a key technical bottleneck restricting the decommission of uranium mine, and the microbial-induced calcium carbonate precipitation (MICP) technology can well mineralize and remove heavy metals in the groundwater.PurposeThis study aims to remove the pollutants in groundwater of uranium mining areas with MICP.MethodsFirst of all, bacillus pasteurianus was selected, and its acid resistance and tolerance to uranium were analyzed. Then, the effects of initial U(VI) concentration, initial Ca2+ concentration, initial pH value, concentration of bacterial solution, and the time of mineralization on the removal of pollutants by MICP were explored. In addition, scanning electron microscopy (SEM) and X-ray diffraction spectroscopy (XRD) were employed to characterize the composition and microstructure of the mineralization products of MICP, in order to reveal the mechanism of mineralization and decontamination. Finally, water with low uranium concentration was treated by bacillus pasteurianus to verify the application of MICP.ResultsThe results show that Bartonella pasteurii has good urease activity at pH value of 4 and can adapt to the groundwater containing U(VI) concentration of 100 mg∙L-1. When the initial pH value is 4, the initial uranium concentration is 50 mg∙L-1, the Ca2+ concentration is 8 000 mg∙L-1, and the time of mineralization by MICP is 48 h, the removal rates of U(VI) and Ca2+ in the groundwater are 61% and 54%, respectively. The removal rate of U(VI) further increases to 91% when the initial pH value is increased to 7. Meanwhile, the increase of Ca2+ concentration promotes the removal of U(VI) in groundwater by MICP, however, the removal rate of Ca2+ is relatively low if the concentration of Ca2+ is too high.ConclusionsThe composition of MICP mineralization products is mainly uranium-containing calcium carbonate, in which the uranium is immobilized mainly by co-precipitation. Therefore, Bacillus pasteurianus can well remove U(VI) and Ca2+ in the groundwater of the mining area of in-situ leaching of uranium, and has a good prospect of application

Preparation and Photocatalytic Performance of ZnO/Sepiolite Composite Materials

Photocatalytic technology is a widely used water treatment method, whose efficiency can be increased by developing a suitable photocatalyst fabrication procedure. In this study, five different synthesis methods were utilised for the preparation of novel ZnO/sepiolite photolytic composites, namely, sol-gel method, hydrothermal reduction, hydrolytic precipitation, powder sintering, and impregnation-reduction. The obtained photocatalysts were characterised by scanning electron microscopy, infrared spectroscopy, and X-ray diffraction. The differences between the applied photocatalyst preparation methods and the reasons for these differences were discussed, and the photocatalytic activities of the prepared composite materials were compared. The obtained results revealed that the physical structure, chemical properties, and photocatalytic performance of the composite produced by the sol-gel method were superior to those of the materials fabricated by the other four methods. Moreover, this material also exhibited high photocatalytic stability, while its photocatalytic degradation of methylene blue dye proceeded via a quasi-first-order reaction. The prepared composites have broad application prospects in photocatalysis and can be potentially used for treating environmental pollutants

Experimental Study on the Mechanical Properties and Damage Evolution of Hollow Cylindrical Granite Specimens Subjected to Cyclic Coupled Static-Dynamic Loads

To study the characteristics of roadway surrounding rock damage caused by frequent disturbances under different static stress conditions, cyclic impact tests on granite with vertical holes under different axial prestress conditions were performed by a modified split Hopkinson pressure bar test, and the damage of the specimens was recorded with a high-speed camera process. The test results show that under the same air pressure cyclic impact, the rock specimens mainly undergo the compaction-fatigue-failure transition. As the axial prestress increases, the compaction-fatigue phase gradually weakens, and the dynamic compressive strength decreases. When the axial prestress is 42% of the UCS and 62% of the UCS, the rock specimen shows a certain “strengthening” effect during the initial cyclic impact stage. During the failure of the rock specimens, the axial prestressing effect limited the initiation of some transverse cracks, and a mixed tensile-shear failure mode appeared. The rock specimens with an axial prestress of 62% of the UCS showed energy release during cyclic impact. To some extent, the probability of “rock bursts” has been induced. Based on the one-dimensional stress wave theory, the damage variables of wave impedance during the cyclic impact loading of the rock with vertical holes are defined. It is found that when the rock specimen is in the stage of compaction and fatigue damage, the damage is small, and the damage is even reduced

Asymmetric Effects of Regulatory Focus on Expected Desirability and Feasibility of Embracing Self-Service Technologies

This research draws on regulatory focus theory to examine the asymmetric effects of regulatory focus (promotion focus versus prevention focus) on expected desirability and feasibility of using self-service technologies (SSTs) in a retail setting. To study consumers' SST trial intention from the perspective of regulatory focus theory, this research first integrates the attributes of SSTs explored in prior studies into a desirability-feasibility framework. The proposed asymmetric effects of regulatory focus (promotion focus versus prevention focus) lie in both scope (on desirability, feasibility, versus both desirability and feasibility) and valence (positive versus negative): The promotion focus facilitates consumers to recognize both desirability (consumption value) and feasibility of using SSTs, whereas the prevention focus inhibits consumers from understanding the feasibility-related attributes of SSTs. In addition, it is proposed that the promotion focus contributes to the easement of consumers' technology anxiety, whereas the prevention focus has a reverse effect. Furthermore, expected desirability (consumption value) and feasibility both positively influence consumers' intention to adopt SSTs, whereas technology anxiety negatively affects consumers' trial intention. Structural equation modeling is used to test the overall model, and the results support the hypotheses in general. © 2012 Wiley Periodicals, Inc.Link_to_subscribed_fulltex

Phosphorus Species, Influencing and Release Risks Assessment in Mangrove Wetland Sediments of Dongzhai Harbor on Hainan Island, China

Mangrove wetlands are superior sites for the deposition of various pollutants, but they are also more susceptible to environmental contamination. To investigate the health threats of phosphorus to mangrove ecosystems, this study presents the distribution, chemical speciation and factors influencing phosphorus (P) forms in 38 surface sediments from the mangrove wetlands of Dongzhai Harbor on Hainan Island, China. P forms were measured using the sequential extraction (SEDEX) procedures. The results showed that the total phosphorus content in the sediment was at a high level, and there was a significant spatial variability of phosphorus in each form. Among them, inorganic phosphorus accounted for 74.64% of the total phosphorus, and organic phosphorus accounted for 25.35% of the total phosphorus. Among the inorganic phosphorus, detrital limestone phosphorus and Ca-bound phosphorus were dominant, while the content of exchangeable phosphorus and Fe-bound phosphorus had a smaller percentage. The concentration of biologically available phosphorus, ranged from 1.76 umol/g to 18.57 umol/g, and the Fe-bound and organic forms of phosphorus had a controlling effect on it. Based on Corg/OP, N/P and land use surveys, it was concluded that phosphorus was mainly an exogenous input. The correlation analysis concluded that the main sources of phosphorus in the study area are agriculture and aquaculture. The development of agriculture and aquaculture led to moderate levels of phosphorus pollution in the study area as a whole, with more serious a phosphorus pollution at the wetland park in the southeast corner of Dongzhai Harbor and in the western areas, with lush vegetation and developed river systems, mainly influenced by human activities, topography, vegetation and water system conditions

Wide Swath and High Resolution Airborne HyperSpectral Imaging System and Flight Validation

Wide Swath and High Resolution Airborne Pushbroom Hyperspectral Imager (WiSHiRaPHI) is the new-generation airborne hyperspectral imager instrument of China, aimed at acquiring accurate spectral curve of target on the ground with both high spatial resolution and high spectral resolution. The spectral sampling interval of WiSHiRaPHI is 2.4 nm and the spectral resolution is 3.5 nm (FWHM), integrating 256 channels coving from 400 nm to 1000 nm. The instrument has a 40-degree field of view (FOV), 0.125 mrad instantaneous field of view (IFOV) and can work in high spectral resolution mode, high spatial resolution mode and high sensitivity mode for different applications, which can adapt to the Velocity to Height Ratio (VHR) lower than 0.04. The integration has been finished, and several airborne flight validation experiments have been conducted. The results showed the system’s excellent performance and high efficiency