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Systematic principles of surrounding rock control in longwall mining within thick coal seams

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International Journal of Mining Science and Technology 2019年第1期29卷 65-71页

作者： Jiachen Wang Zhaohui Wang faculty of resources and Safety engineering China University of Mining&TechnologyBeijing

Effective surrounding rock control is a prerequisite for realizing safe mining in underground coal *** the past three decades, longwall top-coal caving mining(LTCC) and single pass large height longwall mining(SPLL) found expanded usage in extracting thick coal seams in China. The two mining methods lead to large void space left behind the working face, which increases the difficulty in ground *** face failure is a common problem in both LTCC and SPLL mining. Such failure is conventionally attributed to low strength and high fracture intensity of the coal seam. However, the stiffness of main components included in the surrounding rock system also greatly influences longwall face ***, surrounding rock system is developed for LTCC and SPLL faces in this paper. The conditions for simultaneous balance of roof structure and longwall face are put forward by taking the stiffness of coal seam, roof strata and hydraulic support into account. The safety factor of the longwall face is defined as the ratio between the ultimate bearing capacity and actual load imposed on the coal *** influences provided by coal strength, coal stiffness, roof stiffness, and hydraulic support stiffness,as well as the movement of roof structure are analyzed. Finally, the key elements dominating longwall face stability are identified for improving surrounding rock control effectiveness in LTCC and SPLL faces.

关键词： Longwall top coal caving mining Single pass large height longwall mining Surrounding rock system Longwall face stability

A New Dinuclear Gadolinium Complex Constructed from p-Phenylenediamine-N,N,N′,N′-tetraacetic Acid and in situ Generated Oxalate

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Chinese Journal of Structural Chemistry 2012年第9期31卷 1315-1321页

作者：于方永郝志峰李海峰胡升 faculty of Chemical engineering and Light Industry Guangdong University of Technology

Routine solution reaction of Gd3＋ and p-phenylenediamine-N,N,N′,N′-tetraacetic acid （p-PhDTA） yields a dinuclear complex [Gd2（ox）（p-PhDTA）2（H2O）10]·6H2O （ox = oxalate）, which was characterized by single-crystal X-ray diffraction （MoKα radiation, = 0.71073）, elemental analysis and IR. This complex crystallizes in the monoclinic system, space group P21/n with a = 10.2522（8）, b = 10.0053（8）, c = 23.8834（18）, = 99.1080（10）°, V = 2419.0（3）3, Z = 2, Mr = 1367.32, Dc = 1.877 g/cm3, F（000） = 1368, = 2.830 mm-1, the final R = 0.0337 and wR = 0.0794 for 4747 observed reflections （I 〉 2 （I））. The exo-tetradentate oxalate ligand, generated in situ from the oxidative coupling of methanol, is incorporated to construct a dinuclear Gd2（ox）2 unit decorated with p-PhDTA ligands on the two sides with a monodentate coordination mode. The dinuclear molecules are further connected by the lattice water molecules to form a three-dimen- sional hydrogen network.

关键词： Gd(III) complex crystal structure p-phenylenediamine-N,N,N',N'-tetraaceticacid oxalate

Influence of Adding Ti Powder in Preform on Microstructure and Mechanical Properties of Al_2O_3p/Steel Composites by Squeeze Casting

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Journal of Wuhan University of Technology(Materials Science) 2018年第1期33卷 164-170页

作者：卢德宏 WANG Jian YU Jing JIANG Yehua faculty of Materials Science and engineering Kunming University of Science and Technology

To improve the mechanical properties of alumina particulates reinforced steel matrix composite, Ti powder was added into the alumina preform, a 5140 steel matrix composite was fabricated by squeeze casting, and the influences of Ti powder on the microstructure, hardness and bending strength of the composite were investigated, compared with the composite without adding Ti powder. Applied Ti powder and alumina particulates were 10-25 μm and 100-180 μm in size, respectively. Both composites were successfully fabricated, however Ti powder addition increased the infiltration thickness of the composite. In the Ti contained composite, a TiC film in micron scale is formed on the surface of alumina particles, many TiC aggregates are dispersed in the steel matrix without obvious remaining Ti powder. The hardness and the three-point bending strength of the composite reach 49.5 HRC and 1 018 MPa, respectively, which are 17.9% and 52.4% higher than those of the composite in the absence of Ti addition. Fracture morphology shows that the debonding of alumina particulates is eliminated for the composite in the presence of Ti addition. Sessile drop test shows the average wetting angle between 5140 steel and that of Ti coated Al2O3 is about 82.15°, much lower than the wetting angle 150° between steel and pure Al2O3. Therefore, the increase in the mechanical properties of the composite is attributed to the improvement of Al2O3 p/steel interface wetting and bonding by adding Ti powder in the preform.

关键词： squeeze casting Al2O3 steel matrix composites interface mechanical properties

Slope Stability Analysis Based on Group Decision Theory and Fuzzy Comprehensive Evaluation

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Journal of Earth Science 2020年第6期31卷 1121-1132页

作者： Peng Xia Xinli Hu Shuangshuang Wu Chunye Ying Chang Liu faculty of engineering China University of GeosciencesWuhan 430074China

A slope stability evaluation method is proposed combining group decision theory,the analytic hierarchy process and fuzzy comprehensive *** index weight assignment of each evaluation element is determined by group decision theory and the analytic hierarchy process,and the membership degree of each indicator is determined based on fuzzy set *** to the weights and memberships,the membership degrees of the criterion layer are obtained by fuzzy operations to evaluate the slope *** results show that(1)the evaluation method comprehensively combines the effects of multiple factors on the slope stability,and the evaluation results are accurate;(2)the evaluation method can fully leverage the experience of the expert group and effectively avoid evaluation errors caused by the subjective bias of a single expert;(3)based on a group decision theory entropy model,this evaluation method can quantitatively evaluate the reliability of expert decisions and effectively improve the efficiency of expert group discussion;and(4)the evaluation method can transform the originally fuzzy and subjective slope stability evaluation into a quantitative evaluation.

关键词： group decision theory analytic hierarchy process fuzzy comprehensive evaluation slope stability

Structural, Elastic, and Electronic Properties of a New Phase of Carbon

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Communications in Theoretical Physics 2015年第8期64卷 237-243页

作者：邢孟江李彬华余正涛陈颀 faculty of Information engineering & Automation Kunming University of Science and Technology

Based on density function theory with the ultrasoft pseudopotential scheme in the frame of the local density approximation and the generalized gradient approximation, the structural, elastic, and electronic properties of carbon with P2221 phase have been systematically studied in this paper. The calculated results show that the P2221 phase of carbon is mechanically stable and dynamically stable at ambient pressure. The anisotropy studies of Young's modulus,Poisson's ratio, shear anisotropic factor, the percentage of elastic anisotropy for bulk modulus, the percentage of elastic anisotropy for shear modulus and the universal anisotropic index show that P2221 phase of carbon exhibits *** addition, P2221 phase is an indirect semiconductor with bandgap of 3.423 e V. But, the band gap of P2221 phase for carbon increase with increasing pressure.

关键词： elastic properties anisotropic properties electron

Fabrication and characterization of GNPs and CNTs reinforced Al7075 matrix composites through the stir casting process

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International Journal of Minerals,Metallurgy and Materials 2021年第7期28卷 1204-1214页

作者： Siavash Imanian Ghazanlou Beitallah Eghbali faculty of Materials engineering Sahand University of TechnologyTabriz 51335-1996Iran

This study investigated the effects of adding graphene nanoplates(GNPs)and carbon nanotubes(CNTs)into the Al7075 matrix via the stir casting method on the microstructure and mechanical properties of the fabricated *** increasing the volume fraction of rein-forcements,the fraction of porosity *** X-ray diffraction results showed that the addition of reinforcements into the Al7075 changed the dominant crystal orientation from(002)to(111).Field emission scanning electron microscopy images also showed the distribution of clustered reinforcements in the *** the two reinforcements,the addition of CNTs generated a lower fraction of *** the addition of 0.52vol%GNPs into the matrix,the hardness,ultimate tensile strength and uniform elongation increased by 44%,32%,and 180%,***,the presence of 0.71vol%CNTs in the matrix increased the hardness,tensile strength and uniform elongation by 108%,129%,and 260%,respectively.

关键词： Al7075 GNPs CNTs stir casting composite

EFFECTS OF AQUATIC VEGETATION ON FLOW IN THE NANSI LAKE AND ITS FLOW VELOCITY MODELING

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Journal of Hydrodynamics 2006年第6期18卷 640-648页

作者： WANG Chao ZHU Ping WANG Pei-fang ZHANG Wen-ming Key Laboratory of Integrated Regulation and resource Development on Shallow Lakes Ministry of EducationCollege of Environmental Science and Engineering Hohai University Nanjing 210098 China

Aquatic vegetation has significant effects on flow in waters. In this article, four types of water areas were analyzed according to the field survey on water depth and vegetation in the Nansi Lake for the East Line Project of water Transfer from South to North in China （WTSNC）. The depth-averaged 2-D hydrodynamic models with and without consideration of the effects of aquatic vegetation on flow were established to simulate flow fields in vegetated and non-vegetated zones in the Nansi Lake. With the established models, flow fields were predicted under the conditions of water transfer from south to north. The results indicate that when the drag force term exerted by aquatic vegetation is considered, the computed velocities agree well with the measured data, whereas as the drag term is taken into account, the computed velocities are obviously larger than the measured data in the vegetated zone and considerably smaller in the non-vegetated zone, and the error range between the two velocities is large if this problem is dealt with the method of increasing the roughness coefficient of the lake-bed to reflect the vegetation drag force. In addition, it is demonstrated that the emerged vegetation exerts larger effects on flow than submerged vegetation comparing the results in the Emerged Vegetation （reed） Zone （EVZ） and the Submerged Vegetation Zone （SVZ）.

关键词： Nansi Lake aquatic vegetation drag force,flow modeling

Effect of struvite and organic acids on immobilization of copper and zinc in contaminated bio-retention filter media

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Journal of Environmental Sciences 2020年第11期32卷 35-44页

作者： Chathurani Moragaspitiya Jay Rajapakse Graeme J.Millar Science and engineering faculty Queensland University of Technology(QUT)Queensland 4000Australia

Few studies have been carried out to connect nutrient recovery as struvite from wastewater and sustainable utilization of the recovered struvite for copper and zinc immobilization in contaminated *** study revealed the effect of struvite on Cu and Zn immobilization in contaminated bio-retention soil in the presence of commonly exuded plant organic *** research hypothesis was that the presence of both struvite and organic acids may influence the immobilization of Cu and Zn in *** outcome of this research confirmed that more than 99%of Cu and Zn was immobilized in bio-retention filter media by struvite ***-soluble Cu and Zn concentrations of struvite treated soil were less than 1.83 and 0.86 mg/kg respectively,and these concentrations were significantly lower compared to the total Cu and Zn content of 747.05 mg/kg in the contaminated *** of struvite to Cu-and Zn-contaminated soil resulted in formation of compounds similar to zinc phosphate tetrahydrate(Zn3(PO4)2·4H2O)and amorphous Cu and Zn *** was effective in heavy metal remediation in acidic soil regardless of the presence of Ca impurities in struvite and the presence of plant organic acids in ***,this study revealed that struvite recovered from wastewater treatment plants has potential for use as an amendment for heavy metal remediation in contaminated bio-retention soil.

关键词： Immobilization Struvite Organic acids Heavy metal Contaminated soil Bio-retention

SEMI-ANALYTICAL SOLUTION FOR FREE VIBRATION OF THICK FUNCTIONALLY GRADED PLATES RESTED ON ELASTIC FOUNDATION WITH ELASTICALLY RESTRAINED EDGE

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Acta Mechanica Solida Sinica 2011年第4期24卷 340-354页

作者： M.Shaban M.M.Alipour faculty of Mechanical engineering Islamic azad University Parand Branch

This paper deals with free vibration analysis of functionally graded thick circular plates resting on the Pasternak elastic foundation with edges elastically restrained against translation and *** equations are obtained based on the first order shear deformation theory（FSDT） with the assumption that the mechanical properties of plate materials vary continuously in the thickness direction.A semi-analytical approach named differential transform method is adopted to transform the differential governing equations into algebraic recurrence *** eigenvalue equation for free vibration analysis is solved for arbitrary boundary *** between the obtained results and the results from analytical method confirms an excellent accuracy of the present ***,comprehensive studies on the FG plates rested on elastic foundation are *** effects of parameters,such as thickness-to-radius,material distribution,foundation stiffness parameters,different combinations of constraints at edges on the frequency,mode shape and modal stress are also investigated.

关键词： free vibration thick circular plates two-parameter elastic foundation elasticallyrestrained edges