制备出了 POD (聚恶二唑)薄膜,测定了 POD 薄膜试样在热解炭化期间的化学结构和重量变化,研究了 POD 薄膜的炭化行为。随着热解温度的提高,POD 大分子在氧二氮茂环处发生断裂,形成具有共轭腈基苯的化合物。新生成的>C=N—和—N=C=O ...制备出了 POD (聚恶二唑)薄膜,测定了 POD 薄膜试样在热解炭化期间的化学结构和重量变化,研究了 POD 薄膜的炭化行为。随着热解温度的提高,POD 大分子在氧二氮茂环处发生断裂,形成具有共轭腈基苯的化合物。新生成的>C=N—和—N=C=O 基团继续进行反应,其中—N=C=O 基团通过耦合反应生成炭化二亚胺(—N=C=N—);再经分子链环化转变成具有吡啶型大共轭结构的多环化合物,继而稠环芳构化生成类石墨芳香族六角网状层面结构。另外,POD 薄膜在1 000℃热解炭化后其重量也发生了很大变化,收率为45.92%。展开更多
使用大型通用有限元软件AN SY S建立了某桥的成桥阶段和施工最不利阶段的有限元模型,分析了模型的动力特性.根据POD型的谱表示法模拟了桥梁的脉动风速场并进行了相关性拟合检验,然后基于准定常理论计算了作用在模型上的抖振力时程.最后...使用大型通用有限元软件AN SY S建立了某桥的成桥阶段和施工最不利阶段的有限元模型,分析了模型的动力特性.根据POD型的谱表示法模拟了桥梁的脉动风速场并进行了相关性拟合检验,然后基于准定常理论计算了作用在模型上的抖振力时程.最后由HHT方法进行时程分析,分别求得了两种模型的抖振时域分析的结果,据此有效地评价了桥的抗风性能.展开更多
In this study, a classical spectral-finite difference scheme （SFDS） for the three-dimensional （3D） parabolic equation is reduced by using proper orthogonal decomposition （POD） and singular value decomposition （...In this study, a classical spectral-finite difference scheme （SFDS） for the three-dimensional （3D） parabolic equation is reduced by using proper orthogonal decomposition （POD） and singular value decomposition （SVD）. First, the 3D parabolic equation is discretized in spatial variables by using spectral collocation method and the discrete scheme is transformed into matrix formulation by tensor product. Second~ the classical SFDS is obtained by difference discretization in time-direction. The ensemble of data are comprised with the first few transient solutions of the classical SFDS for the 3D parabolic equation and the POD bases of ensemble of data are generated by using POD technique and SVD. The unknown quantities of the classical SFDS are replaced with the linear combination of POD bases and a reduced- order extrapolation SFDS with lower dimensions and sufficiently high accuracy for the 3D parabolic equation is established. Third, the error estimates between the classical SFDS solutions and the reduced-order extrapolation SFDS solutions and the implementation for solving the reduced-order extrapolation SFDS are provided. Finally, a numerical example shows that the errors of numerical computations are consistent with the theoretical results. Moreover, it is shown that the reduced-order extrapolation SFDS is effective and feasible to find the numerical solutions for the 3D parabolic equation.展开更多
文摘制备出了 POD (聚恶二唑)薄膜,测定了 POD 薄膜试样在热解炭化期间的化学结构和重量变化,研究了 POD 薄膜的炭化行为。随着热解温度的提高,POD 大分子在氧二氮茂环处发生断裂,形成具有共轭腈基苯的化合物。新生成的>C=N—和—N=C=O 基团继续进行反应,其中—N=C=O 基团通过耦合反应生成炭化二亚胺(—N=C=N—);再经分子链环化转变成具有吡啶型大共轭结构的多环化合物,继而稠环芳构化生成类石墨芳香族六角网状层面结构。另外,POD 薄膜在1 000℃热解炭化后其重量也发生了很大变化,收率为45.92%。
文摘使用大型通用有限元软件AN SY S建立了某桥的成桥阶段和施工最不利阶段的有限元模型,分析了模型的动力特性.根据POD型的谱表示法模拟了桥梁的脉动风速场并进行了相关性拟合检验,然后基于准定常理论计算了作用在模型上的抖振力时程.最后由HHT方法进行时程分析,分别求得了两种模型的抖振时域分析的结果,据此有效地评价了桥的抗风性能.
基金This work was supported in part by the National Natural Science Foundation of China （Grant Nos. 11271127, 11361035）, the Doctoral Foundation of Guizhou Normal University, and the Science and Technology Fund of Guizhou Province （Grant No. 7052） in 2014.
文摘In this study, a classical spectral-finite difference scheme （SFDS） for the three-dimensional （3D） parabolic equation is reduced by using proper orthogonal decomposition （POD） and singular value decomposition （SVD）. First, the 3D parabolic equation is discretized in spatial variables by using spectral collocation method and the discrete scheme is transformed into matrix formulation by tensor product. Second~ the classical SFDS is obtained by difference discretization in time-direction. The ensemble of data are comprised with the first few transient solutions of the classical SFDS for the 3D parabolic equation and the POD bases of ensemble of data are generated by using POD technique and SVD. The unknown quantities of the classical SFDS are replaced with the linear combination of POD bases and a reduced- order extrapolation SFDS with lower dimensions and sufficiently high accuracy for the 3D parabolic equation is established. Third, the error estimates between the classical SFDS solutions and the reduced-order extrapolation SFDS solutions and the implementation for solving the reduced-order extrapolation SFDS are provided. Finally, a numerical example shows that the errors of numerical computations are consistent with the theoretical results. Moreover, it is shown that the reduced-order extrapolation SFDS is effective and feasible to find the numerical solutions for the 3D parabolic equation.
