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Xie T.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Xu L.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Liu C.,Chongqing University | Yang J.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Wu W.,Chongqing University
Vacuum | Year: 2013

A kind of hard-magnetic material, strontium ferrite (SrFe 12O19) was prepared using Industrial Strontium Residue (ISR) as starting material. To optimize the conditions of recovery ratio of strontium element, the orthogonal design was carried out. The results showed the recovery ratio reached to 96.73%. The processes of recovery and preparation were suitable to industrial production. This research was therefore expected to reuse efficiently the ISR and prevent its environmental pollution. The prepared products were characterized by FTIR, XRD, SEM, and VSM. The results indicated the prepared SrFe12O19 could be classified as hexagonal crystal with a better magnetic property. The Langmuir and BET models were separately used to calculate the specific surface area of the prepared SrFe 12O19. The error analysis was performed by a comparison between experimental data and value calculated. These investigations revealed BET adsorption equation was more suitable for the surface area analysis of SrFe12O19. The N2 adsorption on the surface of SrFe12O19 could be categorized as multilayer adsorption. The specific surface area (BET) of SrFe12O19 was 31.2434 m2/g. © 2013 Elsevier Ltd. All rights reserved.


Zhang X.,Key Laboratory of Dependable Service Computing | Zhang X.,Chongqing University | Zhang X.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Qu Y.,Chongqing University | And 3 more authors.
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2015

Scale-space behavior of corners is important for developing an efficient corner detection algorithm. In this paper, we analyze the scale-space behavior with the Laplacian of Gaussian (LoG) operator on a planar curve which constructs Laplacian Scale Space (LSS). The analytical expression of a Laplacian Scale-Space map (LSS map) is obtained, demonstrating the Laplacian Scale-Space behavior of the planar curve corners, based on a newly defined unified corner model. With this formula, some Laplacian Scale-Space behavior is summarized. Although LSS demonstrates some similarities to Curvature Scale Space (CSS), there are still some differences. First, no new extreme points are generated in the LSS. Second, the behavior of different cases of a corner model is consistent and simple. This makes it easy to trace the corner in a scale space. At last, the behavior of LSS is verified in an experiment on a digital curve. © 2015 IEEE.


Xie T.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Xu L.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Liu C.,Chongqing University
RSC Advances | Year: 2013

Sr-Zn ferrite composites were synthesized by chemical coprecipitation with different sintering process. The composites were characterized by XRD, XPS, IR, VSM, and N2-adsorption. The results revealed that the composites were composed of S-type ZnFe2O4 and M-type SrFe 12O19. Zn2+ ions inserted and occupied the 12k or 2a sites for Fe3+ ions in M-type SrFe12O19. The Zn2+ ions were therefore not on the external surface of the composites. The microwave absorption properties at a frequency range of 0-18 GHz were estimated using the electromagnetic parameters obtained through the agency of microwave vector network analyzer. The microwave absorbing properties of composites were excellently superior to that of the pure SrFe12O 19 or ZnFe2O4 due mainly to the exchange coupling between the hard- and soft-magnetic phases. The synthesis process was found to facilitate mass production for various composite materials, especially the two phases or multiphase composite materials. © 2013 The Royal Society of Chemistry.


Wang J.-L.,China University of Mining and Technology | Liu G.-J.,Hefei University of Technology | Wang W.-Z.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Zhang S.-J.,China University of Mining and Technology | Yuan L.-L.,China University of Mining and Technology
Meitan Xuebao/Journal of the China Coal Society | Year: 2013

The shale samples were collected from the Longmaxi Formation of Lower Silurian in southern Sichuan Basin. The pore-fissure structures of shale samples were measured and their characteristics were analyzed in this study. Based on the different superiority distribution of pore-fissure, the structures of pore-fissure was divided into three types: pore-superior distribution, fissure-superior distribution and pore-fissure equipotent distribution. In different conditions of axial compression, confining pressure and gas pressure gradient, the CH4 seepage experiments of some shale samples were carried out in three-dimensional stress field. Also, the effect of effective stress and gas slippage effect on the absolute permeability(K0) of shale were calculated and analyzed. It reveals that the permeability K0 and stress difference have negative exponential correlation on the condition of low pressure gradient. The permeability K0 and pressure gradient also have negative exponential correlation. The permeability K0 attenuates observably as the pressure gradient ranges from 0 to 0.2 MPa. It concludes that the effective stress increase will lead to micro-fissures closing and permeability decreasing. The adverse effect of matrix shrinkage and gas slippage effect coexist in the process of pressure gradient increasing while the contribution of slippage effect to permeability is lower than the adverse effect of matrix shrinkage. The shale permeability is different under the condition of different stresses. The shale permeability itself shows non-uniformity which implicates the difference of its micro-fissures development.


Song C.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Lu Y.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Jia Y.,State Key Laboratory of Coal Mine Disaster Dynamics and Control
ISRM International Symposium - 8th Asian Rock Mechanics Symposium, ARMS 2014 | Year: 2014

To investigate the natural fractures 'effect on hydraulic fracturing crack propagation in the coal seam, the two-dimensional model of hydraulic fracturing crack intersecting natural fractures is built. Based on it, the laws of crack propagation and failure mechanism of natural fractures are studied by using the method of theoretical analysis and numerical simulation. The research suggests that angle of interaction between main crack and natural fracture, the horizontal differential principal stress and the development degree of natural fractures are the three main factors that affect direction of crack propagation. The direction of the propagation of crack tends along natural fracture due to shear failure in condition of low horizontal differential principal stress and low angle of interaction; Besides, with the increase of horizontal differential principal stress or angle of interaction the propagating fracture tends to cross the natural fracture. The small size of natural fracture had little or no effect on the direction of the propagation of hydraulic fracture whereas the propagating fracture turns to natural fracture's direction when the size of natural fracture is large. © 2014 by Japanese Committee for Rock Mechanics.


Si H.,Chongqing University | Si H.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Xue Y.-Z.,Chongqing University | Xue Y.-Z.,State Key Laboratory of Coal Mine Disaster Dynamics and Control
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2016

Using the method of smooth particle hydrodynamics (SPH) to analyze the dynamic process of pulse jets' breaking rock is an efficient way to avoid mesh distortion problems occurring in the traditional finite element method (FEM) to deal with large deformation problems. Here, a numerical calculation model of pulse jets' breaking rock was built by introducing the J-H-C model and using the SPH method. The formation, propagation and attenuation of stress waves during the process of rock broken were simulated with this method. Through analyzing stress wave changing laws in time and space, stress wave patterns figures in the propagation process were drawn. The time domain characteristics and spacial characteristics of stress waves propagation during pulse jets' breaking rock were analyzed. It was shown that the propagation characteristics of stress waves and their damage offect in different rock mediums are different. The calculation results were explained according to rock properties and wave propagation characteristics. The results of numerical simulation agreed well with those of the actual cases and provided a guide for engineering applications. © 2016, Editorial Office of Journal of Vibration and Shock. All right reserved.


Xie T.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Xu L.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Liu C.,Chongqing University | Cheng W.,Chongqing University
Journal of Materials Engineering and Performance | Year: 2013

Magnetic solid acid catalysts (SO4 2-/ZrO 2-SrFe12O19) were synthesized by loading SO4 2-/ZrO2 onto strontium ferrite (SrFe 12O19). The properties of the magnetic solid acid catalysts were investigated with x-ray powder diffraction (XRD), Fourier transformation infrared (FTIR) spectra, vibrating sample magnetometer (VSM), and Brunauer-Emmett-Teller (BET). The catalytic activity of the as-prepared catalyst was probed through synthesis of n-butyl acetate. The results showed that the SrFe12O19 could improve the crystalline phase transition temperature of ZrO2 and stabilize the metastable tetragonal phase (t-ZrO2) at 600 °C. The saturation magnetization (Ms) and coercivity (Hc) of catalyst sintered at 600 °C were 16.8 emu/g and 4412 G, respectively, which conduced towards the recovery and reuse of the catalyst. After the catalyst was reused four times, the yield was still more than 70%, which revealed the catalyst had a high activity and better stability. © ASM International.


Xie T.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Xu L.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Liu C.,Chongqing University | Wang Y.,Chongqing University
Applied Surface Science | Year: 2013

One-step chemical coprecipitation with high-temperature sintering method was employed for preparing magnetic composite ZnFe2O 4/SrFe12O19 including a hard-magnetic phase (SrFe12O19) and a soft-magnetic phase (ZnFe 2O4). The magnetic composite was characterized by FTIR, XRD, SEM, BET, XPS, VSM, and UV-vis. The testing results showed that the saturation magnetization (Ms), remanent magnetization (M r), and coercivity (Hc) were 34.95 emu/g, 18.31 emu/g, and 2254.54 G, respectively, indicating that the composite possessed excellent magnetic properties and a greater capacity for anti-demagnetize. The properties of the composite were favourable to its separation, recycling, and reuse after reaction. The photocatalytic performance of the composite was studied by the degradation reaction of methylene blue under visible light irradiation. The experimental results revealed that the degradation rate was still more than 70% when the composite was reused for four times. In addition, this research was expected to provide a promising method to prepare various composite materials with multi-functional components. Crown Copyright © 2013 Published by Elsevier B.V. All rights reserved.


Xie T.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Xu L.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Liu C.,Chongqing University
Powder Technology | Year: 2012

The composites SrCo xFe 12-xO 19(x=0-0.3) were prepared by coprecipitation high-temperature sintering method with low-cost reagents. The structures and properties of SrCo xFe 12-xO 19 were characterized by X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) techniques. There were hard magnetic phase (SrFe 12O 19) and soft magnetic phase (CoFe 2O 4) in SrCo xFe 12-xO 19(x=0.05-0.3). The saturation magnetization of SrCo xFe 12-xO 19(x=0.3) was larger than those of SrCo xFe 12-xO 19(x≤0.2). The synthesized composites were fit to act as good magnetic substrate of catalysts. © 2012.


Zhong Z.,Chongqing University | Huang D.,Chongqing University | Huang D.,State Key Laboratory of Coal Mine Disaster Dynamics and Control | Huang R.-Q.,Chengdu University of Technology
Yantu Gongcheng Xuebao/Chinese Journal of Geotechnical Engineering | Year: 2016

The landslide mode of retaining wall collapse is a kind of typical failure mode of large-scale rock slopes. The physical and mechanical properties of the locked patch play a key role in maintaining the stability of such slopes. Based on the force analysis of the slopes, the upper sliding mass can be divided into several calculation slices according to its geological structures (for example, bedding planes), and then the forces (including magnitude and direction) applied on the locked patch can be efficiently determined based on the upper bound method of limit analysis. On the basis of limit shear balance analysis, the safety factor of the locked patch with shear failure mode can be calculated. Xikou landslide in Sichuan is taken as a case study to verify the practical application of the theory proposed by the authors. Firstly, the most dangerous section in the locked patch can be obtained according to the relation between safety factor and dip angle of the shear plane. And then the relationship between the width of the most dangerous section and the safety factor is quantitatively analyzed. These results are of great significance for the stability evaluation and hazard control of the landslides with the failure mode of retaining wall collapse. © 2016, Editorial Office of Chinese Journal of Geotechnical Engineering. All right reserved.

Loading State Key Laboratory of Coal Mine Disaster Dynamics and Control collaborators
Loading State Key Laboratory of Coal Mine Disaster Dynamics and Control collaborators