The asymmetric initial post-buckling corresponding to the lowest bifurcation load and the imperfection sensitivity are analysed in detail for a compressed simply supported column with an equilateral triangular cross-s...The asymmetric initial post-buckling corresponding to the lowest bifurcation load and the imperfection sensitivity are analysed in detail for a compressed simply supported column with an equilateral triangular cross-section in the plastic range. The effect of elastic unloading is taken into ao count in the analysis. The asymptotic relations, including high order terms, among the load, the amplitude of imperfection and the amplitude of the bifurcation mode ark realized. The results show that the maximum supported load is very sensitive to imperfection.展开更多
The plastic post-buckling of a simply supported column with a solid rectangularcross-section is analysed by a new approach. High order terms in the asymptotic post-buckling expansions are carried out. In some aspect...The plastic post-buckling of a simply supported column with a solid rectangularcross-section is analysed by a new approach. High order terms in the asymptotic post-buckling expansions are carried out. In some aspects, the method proposed in thispaper is similar io Hutchinson's. However, the computation is simple since theintroduction is avoided of stretched coordinates. The method can be used to analyseinitial post-bifurcation of plates and shells in the plastic range.展开更多
Based on the assumption of finite deformation, the Hamilton variational principle is extended to a nonlinear elastic Euler-type beam-column structure located on a nonlinear elastic foundation. The corresponding three-...Based on the assumption of finite deformation, the Hamilton variational principle is extended to a nonlinear elastic Euler-type beam-column structure located on a nonlinear elastic foundation. The corresponding three-dimensional （3D） mathematical model for analyzing the nonlinear mechanical behaviors of structures is established, in which the effects of the rotation inertia and the nonlinearity of material and geometry are considered. As an application, the nonlinear stability and the post-buckling for a linear elastic beam with the equal cross-section located on an elastic foundation are analyzed. One end of the beam is fully fixed, and the other end is partially fixed and subjected to an axial force. A new numerical technique is proposed to calculate the trivial solution, bifurcation points, and bifurcation solutions by the shooting method and the Newton- Raphson iterative method. The first and second bifurcation points and the corresponding bifurcation solutions are calculated successfully. The effects of the foundation resistances and the inertia moments on the bifurcation points are considered.展开更多
目的基于HPLC研究柏子仁中4种黄曲霉毒素的污染情况,并进行风险分析,评估柏子仁的用药安全。方法采用Agilent Eclipse Plus C 18(4.6×250 mm 5μm)为色谱柱,柱后光化学衍生法检测,以甲醇∶乙腈∶水(35∶10∶55)为流动相,流速1.0 mL...目的基于HPLC研究柏子仁中4种黄曲霉毒素的污染情况,并进行风险分析,评估柏子仁的用药安全。方法采用Agilent Eclipse Plus C 18(4.6×250 mm 5μm)为色谱柱,柱后光化学衍生法检测,以甲醇∶乙腈∶水(35∶10∶55)为流动相,流速1.0 mL·min^(-1);柱温:40℃;荧光检测器检测。结果黄曲霉毒素B 1、B 2、G 1、G 2分别在0.35~20.8μg·L^(-1)、0.13~7.6μg·L^(-1)、0.36~21.6μg·L^(-1)、0.13~7.6μg·L^(-1)范围内呈良好的线性关系,黄曲霉毒素B 1、B 2、G 1、G 2平均回收率分别为90.6%、83.46%、87.84%、86.58%,相对偏差分别为2.9%、3.6%、3.6%、4.7%。23批柏子仁中有14批检出黄曲霉毒素B 1和总量,残留量分别在1~4μg·kg^(-1)和1~5μg·kg^(-1)之间,均符合规定,但检出率高达61%,存在安全隐患。结论该方法简单、准确、方便,能有效评价柏子仁中黄曲霉毒素的污染情况。警示柏子仁易受黄曲霉毒素的污染,需加强柏子仁监管力度和不定期的专项抽检,降低安全风险,以确保临床用药安全。展开更多
Fiber Reinforced Polymer （FRP） composites are an effective material for strengthening circular concrete columns. The effectiveness of FRP confinement for square and rectangular columns is greatly reduced due to stre...Fiber Reinforced Polymer （FRP） composites are an effective material for strengthening circular concrete columns. The effectiveness of FRP confinement for square and rectangular columns is greatly reduced due to stress concentrations at the sharp comers and loss of the membrane effect at the fiat sides of the cross-section. Shape modification can eliminate the effects of column comers and flat sides, and thereby restore the membrane effect and improve the compressive behavior of FRP-confined square and rectangular concrete columns. Shape modification using chemical post-tensioning, achieved by using expansive cement concrete, is described and several mix designs for obtaining the optimal level of expansion are presented. In addition, parametric studies regarding the optimal geometry of the shape-modified cross-section are presented utilizing the analytical model.展开更多
Nowadays, as the increasing marketization of dissemination medium, the competition between the dissemination medium gets hot up. The social television has now entered a new period in which the central task is to compe...Nowadays, as the increasing marketization of dissemination medium, the competition between the dissemination medium gets hot up. The social television has now entered a new period in which the central task is to compete. ＂Brand＂ ＂marketing strategies becomes more important. Brand columns are important. It is to the television channel what product to enterprise. Famous-brand column brings famous-brand column and social benefit. As well as building and maintaining a good brand column needs high quality program content and high standard program form. As well as exquisite column decoration, thereby, TV column packaging became essential.展开更多
文摘The asymmetric initial post-buckling corresponding to the lowest bifurcation load and the imperfection sensitivity are analysed in detail for a compressed simply supported column with an equilateral triangular cross-section in the plastic range. The effect of elastic unloading is taken into ao count in the analysis. The asymptotic relations, including high order terms, among the load, the amplitude of imperfection and the amplitude of the bifurcation mode ark realized. The results show that the maximum supported load is very sensitive to imperfection.
文摘The plastic post-buckling of a simply supported column with a solid rectangularcross-section is analysed by a new approach. High order terms in the asymptotic post-buckling expansions are carried out. In some aspects, the method proposed in thispaper is similar io Hutchinson's. However, the computation is simple since theintroduction is avoided of stretched coordinates. The method can be used to analyseinitial post-bifurcation of plates and shells in the plastic range.
基金Project supported by the National Science Foundation for Distinguished Young Scholars of China(No. 11002084)the Shanghai Pujiang Program (No. 07pj14073)the Scientific Research Projectof Shanghai Normal University (No. SK201032)
文摘Based on the assumption of finite deformation, the Hamilton variational principle is extended to a nonlinear elastic Euler-type beam-column structure located on a nonlinear elastic foundation. The corresponding three-dimensional （3D） mathematical model for analyzing the nonlinear mechanical behaviors of structures is established, in which the effects of the rotation inertia and the nonlinearity of material and geometry are considered. As an application, the nonlinear stability and the post-buckling for a linear elastic beam with the equal cross-section located on an elastic foundation are analyzed. One end of the beam is fully fixed, and the other end is partially fixed and subjected to an axial force. A new numerical technique is proposed to calculate the trivial solution, bifurcation points, and bifurcation solutions by the shooting method and the Newton- Raphson iterative method. The first and second bifurcation points and the corresponding bifurcation solutions are calculated successfully. The effects of the foundation resistances and the inertia moments on the bifurcation points are considered.
文摘Fiber Reinforced Polymer （FRP） composites are an effective material for strengthening circular concrete columns. The effectiveness of FRP confinement for square and rectangular columns is greatly reduced due to stress concentrations at the sharp comers and loss of the membrane effect at the fiat sides of the cross-section. Shape modification can eliminate the effects of column comers and flat sides, and thereby restore the membrane effect and improve the compressive behavior of FRP-confined square and rectangular concrete columns. Shape modification using chemical post-tensioning, achieved by using expansive cement concrete, is described and several mix designs for obtaining the optimal level of expansion are presented. In addition, parametric studies regarding the optimal geometry of the shape-modified cross-section are presented utilizing the analytical model.
文摘Nowadays, as the increasing marketization of dissemination medium, the competition between the dissemination medium gets hot up. The social television has now entered a new period in which the central task is to compete. ＂Brand＂ ＂marketing strategies becomes more important. Brand columns are important. It is to the television channel what product to enterprise. Famous-brand column brings famous-brand column and social benefit. As well as building and maintaining a good brand column needs high quality program content and high standard program form. As well as exquisite column decoration, thereby, TV column packaging became essential.
