In this research,a solid 1%Li/Ca-La mixed oxide catalyst was prepared using co-precipitation method followed by wet impregnation.The prepared catalyst was used in the transesterification reaction of canola oil and met...In this research,a solid 1%Li/Ca-La mixed oxide catalyst was prepared using co-precipitation method followed by wet impregnation.The prepared catalyst was used in the transesterification reaction of canola oil and methanol for biodiesel synthesis.The effects of calcination and reaction temperatures were investigated on the activity of the catalyst.In addition,rate of the reaction was studied through a kinetic model for which parameters were determined.Surface properties and structure of the catalyst were characterized through the powder X-ray diffraction(XRD),thermogravimetry/derivative thermogravimetry(TG/DTG),and Fourier transform infrared spectroscopy analysis.All these emphasized that the performance of the catalyst corresponded to the generation of the active sites and their thermal activation.展开更多
Failure of the surrounding rock around a roadway induced by roof separation is one major type of underground roof-fall accidents.This failure can especially be commonly-seen in a bottom-driven roadway within an extra-...Failure of the surrounding rock around a roadway induced by roof separation is one major type of underground roof-fall accidents.This failure can especially be commonly-seen in a bottom-driven roadway within an extra-thick coal seam("bottom-driven roadway"is used throughout for ease of reference),containing weak partings in their roof coal seams.To determine the upper limit position of the roof interlayer separation is the primary premise for roof control.In this study,a mechanical model for predicting the interlayer separation overlying a bottom-driven roadway within an extra-thick coal seam was established and used to deduce the vertical stress,and length,of the elastic,and plastic zones in the rock strata above the wall of the roadway as well as the formulae for calculating the deflection in different regions of rock strata under bearing stress.Also,an approach was proposed,calculating the stratum load,deflection,and limiting span of the upper limit position of the interlayer separation in a thick coal seam.Based on the key strata control theory and its influence of bedding separation,a set of methods judging the upper limit position of the roof interlayer separation were constructed.In addition,the theoretical prediction and field monitoring for the upper limit position of interlayer separation were conducted in a typical roadway.The results obtained by these two methods are consistent,indicating that the methods proposed are conducive to improving roof control in a thick coal seam.展开更多
Extended finite element method （XFEM） implementation of the interaction integral methodology for evaluating the stress intensity factors （SIF） of the mixed-mode crack problem is presented. A discontinuous function...Extended finite element method （XFEM） implementation of the interaction integral methodology for evaluating the stress intensity factors （SIF） of the mixed-mode crack problem is presented. A discontinuous function and the near-tip asymptotic function are added to the classic finite element approximation to model the crack behavior. Two-state integral by the superposition of actual and auxiliary fields is derived to calculate the SIFs. Applications of the proposed technique to the inclined centre crack plate with inclined angle from 0° to 90° and slant edge crack plate with slant angle 45°, 67.5° and 90° are presented, and comparisons are made with closed form solutions. The results show that the proposed method is convenient, accurate and computationallv efficient.展开更多
为有效表征流体在致密储层CO_(2)驱动态裂缝网络系统的分区闭合及动态储容效应,以及反演动态裂缝网络特征参数,建立一种动态裂缝网络水平井试井模型,采用半解析方法、Laplace转换、动态裂缝特征函数、杜哈美原理和Stehfest数值反演求解...为有效表征流体在致密储层CO_(2)驱动态裂缝网络系统的分区闭合及动态储容效应,以及反演动态裂缝网络特征参数,建立一种动态裂缝网络水平井试井模型,采用半解析方法、Laplace转换、动态裂缝特征函数、杜哈美原理和Stehfest数值反演求解试井模型,获得井底压力响应半解析解,绘制井底压力响应曲线,对动态裂缝闭合速度、井筒储集系数、动态裂缝网络半径和动态储容比进行敏感性分析。结果表明:考虑致密储层CO_(2)驱动态裂缝网络的压力图版与常规压力图版存在显著差异;井底压力响应曲线呈异常尖峰和额外双水平线特征,ψ′wD t D<0.5;动态裂缝闭合速度、动态裂缝网络半径及动态储容比对井底压力响应影响较大。动态裂缝网络水平井试井模型能有效定量表征致密储层长期注入CO_(2)的动态裂缝网络行为及非稳态渗流规律,为CO_(2)强化致密储层开发提供依据。展开更多
Thermal shocking effect occurs when the coalbed methane(CBM)reservoirs meet liquid nitrogen(LN2)of extremely low temperature.In this study,3D via X-ray microcomputer tomography(μCT)and scanning electron microscope(SE...Thermal shocking effect occurs when the coalbed methane(CBM)reservoirs meet liquid nitrogen(LN2)of extremely low temperature.In this study,3D via X-ray microcomputer tomography(μCT)and scanning electron microscope(SEM)are employed to visualize and quantify morphological evolution characteristics of fractures in coal after LN2 thermal shocking treatments.LN2 thermal shocking leads to a denser fracture network than its original state with coal porosity growth rate increasing up to 183.3%.The surface porosity of theμCT scanned layers inside the coal specimen is influenced by LN2 thermal shocking which rises from 18.76%to 215.11%,illustrating the deformation heterogeneity of coal after LN2 thermal shocking.The cracking effect of LN2 thermal shocking on the surface of low porosity is generally more effective than that of high surface porosity,indicating the applicability of LN2 thermal shocking on low-permeability CBM reservoir stimulation.The characteristics of SEM scanned coal matrix in the coal powder and the coal block after the LN2 thermal shocking presented a large amount of deep and shallow progressive scratch layers,fracture variation diversity(i.e.extension,propagation,connectivity,irregularity)on the surface of the coal block and these were the main reasons leading to the decrease of the uniaxial compressive strength of the coal specimen.展开更多
基金supported by the Iran National Science Foundation(INSF)
文摘In this research,a solid 1%Li/Ca-La mixed oxide catalyst was prepared using co-precipitation method followed by wet impregnation.The prepared catalyst was used in the transesterification reaction of canola oil and methanol for biodiesel synthesis.The effects of calcination and reaction temperatures were investigated on the activity of the catalyst.In addition,rate of the reaction was studied through a kinetic model for which parameters were determined.Surface properties and structure of the catalyst were characterized through the powder X-ray diffraction(XRD),thermogravimetry/derivative thermogravimetry(TG/DTG),and Fourier transform infrared spectroscopy analysis.All these emphasized that the performance of the catalyst corresponded to the generation of the active sites and their thermal activation.
基金Project(2017XKQY012) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(PAPD) supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Failure of the surrounding rock around a roadway induced by roof separation is one major type of underground roof-fall accidents.This failure can especially be commonly-seen in a bottom-driven roadway within an extra-thick coal seam("bottom-driven roadway"is used throughout for ease of reference),containing weak partings in their roof coal seams.To determine the upper limit position of the roof interlayer separation is the primary premise for roof control.In this study,a mechanical model for predicting the interlayer separation overlying a bottom-driven roadway within an extra-thick coal seam was established and used to deduce the vertical stress,and length,of the elastic,and plastic zones in the rock strata above the wall of the roadway as well as the formulae for calculating the deflection in different regions of rock strata under bearing stress.Also,an approach was proposed,calculating the stratum load,deflection,and limiting span of the upper limit position of the interlayer separation in a thick coal seam.Based on the key strata control theory and its influence of bedding separation,a set of methods judging the upper limit position of the roof interlayer separation were constructed.In addition,the theoretical prediction and field monitoring for the upper limit position of interlayer separation were conducted in a typical roadway.The results obtained by these two methods are consistent,indicating that the methods proposed are conducive to improving roof control in a thick coal seam.
基金Projects(41172244,41072224) supported by the National Natural Science Foundation of ChinaProject(2009GGJS-037) supported by the Foundation of Youths Key Teacher by the Henan Educational Committee,China
文摘Extended finite element method （XFEM） implementation of the interaction integral methodology for evaluating the stress intensity factors （SIF） of the mixed-mode crack problem is presented. A discontinuous function and the near-tip asymptotic function are added to the classic finite element approximation to model the crack behavior. Two-state integral by the superposition of actual and auxiliary fields is derived to calculate the SIFs. Applications of the proposed technique to the inclined centre crack plate with inclined angle from 0° to 90° and slant edge crack plate with slant angle 45°, 67.5° and 90° are presented, and comparisons are made with closed form solutions. The results show that the proposed method is convenient, accurate and computationallv efficient.
文摘为有效表征流体在致密储层CO_(2)驱动态裂缝网络系统的分区闭合及动态储容效应,以及反演动态裂缝网络特征参数,建立一种动态裂缝网络水平井试井模型,采用半解析方法、Laplace转换、动态裂缝特征函数、杜哈美原理和Stehfest数值反演求解试井模型,获得井底压力响应半解析解,绘制井底压力响应曲线,对动态裂缝闭合速度、井筒储集系数、动态裂缝网络半径和动态储容比进行敏感性分析。结果表明:考虑致密储层CO_(2)驱动态裂缝网络的压力图版与常规压力图版存在显著差异;井底压力响应曲线呈异常尖峰和额外双水平线特征,ψ′wD t D<0.5;动态裂缝闭合速度、动态裂缝网络半径及动态储容比对井底压力响应影响较大。动态裂缝网络水平井试井模型能有效定量表征致密储层长期注入CO_(2)的动态裂缝网络行为及非稳态渗流规律,为CO_(2)强化致密储层开发提供依据。
基金Project(2017XKQY012)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Thermal shocking effect occurs when the coalbed methane(CBM)reservoirs meet liquid nitrogen(LN2)of extremely low temperature.In this study,3D via X-ray microcomputer tomography(μCT)and scanning electron microscope(SEM)are employed to visualize and quantify morphological evolution characteristics of fractures in coal after LN2 thermal shocking treatments.LN2 thermal shocking leads to a denser fracture network than its original state with coal porosity growth rate increasing up to 183.3%.The surface porosity of theμCT scanned layers inside the coal specimen is influenced by LN2 thermal shocking which rises from 18.76%to 215.11%,illustrating the deformation heterogeneity of coal after LN2 thermal shocking.The cracking effect of LN2 thermal shocking on the surface of low porosity is generally more effective than that of high surface porosity,indicating the applicability of LN2 thermal shocking on low-permeability CBM reservoir stimulation.The characteristics of SEM scanned coal matrix in the coal powder and the coal block after the LN2 thermal shocking presented a large amount of deep and shallow progressive scratch layers,fracture variation diversity(i.e.extension,propagation,connectivity,irregularity)on the surface of the coal block and these were the main reasons leading to the decrease of the uniaxial compressive strength of the coal specimen.
