This paper focuses on the buckling behaviors of a micro-scaled bi-directional functionally graded （FG） beam with a rectangular cross-section, which is now widely used in fabricating components of micro-nano-electro-...This paper focuses on the buckling behaviors of a micro-scaled bi-directional functionally graded （FG） beam with a rectangular cross-section, which is now widely used in fabricating components of micro-nano-electro-mechanical systems （MEMS/NEMS） with a wide range of aspect ratios. Based on the modified couple stress theory and the principle of minimum potential energy, the governing equations and boundary conditions for a micro-structure-dependent beam theory are derived. The present beam theory incorporates different kinds of higher-order shear assumptions as well as the two familiar beam theories, namely, the Euler-Bernoulli and Timoshenko beam theories. A numerical solu- tion procedure, based on a generalized differential quadrature method （GDQM）, is used to calculate the results of the bi-directional FG beams. The effects of the two exponential FG indexes, the higher-order shear deformations, the length scale parameter, the geomet- ric dimensions, and the different boundary conditions on the critical buckling loads are studied in detail, by assuming that Young＇s modulus obeys an exponential distribution function in both length and thickness directions. To reach the desired critical buckling load, the appropriate exponential FG indexes and geometric shape of micro-beams can be designed according to the proposed theory.展开更多
We present a variational density-functional perturbation theory （DFPT） to investigate the lattice dynamics and vibra- tional properties of single crystal bismuth telluride material. The phonon dispersion curves and ...We present a variational density-functional perturbation theory （DFPT） to investigate the lattice dynamics and vibra- tional properties of single crystal bismuth telluride material. The phonon dispersion curves and phonon density of states （DOS） of the material were obtained. The phonon dispersions are divided into two fields by a phonon gap. In the lower field, atomic vibrations of both Bi and Te contribute to the DOS. In the higher field, most contributions come from Te atoms. The calculated Born effective charges and dielectric constants reveal a great anisotropy in the crystal. The largest Born effective charge generates a significant dynamic charge transferring along the c axis. By DFPT calculation, the greatest LO-TO splitting takes place in the infrared phonon modes and reaches 1.7 THz in the Brillouin zone center. The Raman spectra and peaks corresponding to respective atomic vibration modes were found to be in good agreement with the experimental data.展开更多
Based on the difficulties of polysemy in translation,this paper explains the rationality of prototype category theory in polysemy translation.Taking Li Zhaoguo’s English version of Su Wen as the research object,it an...Based on the difficulties of polysemy in translation,this paper explains the rationality of prototype category theory in polysemy translation.Taking Li Zhaoguo’s English version of Su Wen as the research object,it analyzes the polysemy translation of“Jing”,“Zong”,and“Jiu”as examples,and puts forward the translation strategies of polysemy under the guidance of prototype category theory:equivalent substitution between categories,synonymous conversion between categories,transliteration and introspection outside categories,so as to provide reference for the study of polysemy in English translation of texts on traditional Chinese medicine.展开更多
The optimized molecular structure and harmonic vibrational frequencies of a 1,4-bis [ 2-（4-pyridyl）ethenyl]- benzene（BPENB） molecule were calculated via five popular density functional theory（DFI＇） methods. On ...The optimized molecular structure and harmonic vibrational frequencies of a 1,4-bis [ 2-（4-pyridyl）ethenyl]- benzene（BPENB） molecule were calculated via five popular density functional theory（DFI＇） methods. On the basis of the comparison between calculated and experimental results, it is concluded that the B3PW91 and B3LYP methods are superior to the others in optimizing structures, and the BPW91 method reproduces the observed fundamental fre-quencies most satisfactorily.展开更多
橡胶材料因具有良好的抗震、吸能作用,在实际工程中应用广泛.然而橡胶超弹性材料的碰撞属于强非线性问题,分析橡胶材料的接触碰撞和大变形问题对于提高装置的缓冲性能具有重要意义.光滑有限元法(smoothed finite element method,S-FEM)...橡胶材料因具有良好的抗震、吸能作用,在实际工程中应用广泛.然而橡胶超弹性材料的碰撞属于强非线性问题,分析橡胶材料的接触碰撞和大变形问题对于提高装置的缓冲性能具有重要意义.光滑有限元法(smoothed finite element method,S-FEM)是一种弱形式的数值计算方法,相比于传统的有限元方法,光滑有限元法对网格的质量要求不高,允许单元在计算过程中发生较大的变形,且光滑域的构造比较灵活,在不增加自由度的前提下,可以达到较高的精度.在光滑有限元法的基础上,采用双势方法进行接触计算,以充分利用光滑有限元法计算大变形问题的优点和双势方法求解接触力的优势.通过与有限元软件MSC.Marc的数值结果对比,验证了该算法的准确性和能量守恒性,并且分析了摩擦因数对碰撞体的影响.展开更多
Based on the full optimized molecular geometric structures via B3LYP/6-311＋G（2d,p） method, a new gem-dinitro energetic plasticizer, bis（2,2-dinitropropyl ethylene）formal was investigated in order to search for hi...Based on the full optimized molecular geometric structures via B3LYP/6-311＋G（2d,p） method, a new gem-dinitro energetic plasticizer, bis（2,2-dinitropropyl ethylene）formal was investigated in order to search for high-performance energetic material. IR spectrum, heat of formation, and detonation performances were predicted. The bond dissociation energies and bond orders for the weakest bonds were analyzed to investigate the thermal stability of the title compound. The results show that the four N-NO2 BDEs are nearly equal to the values of 164.38 kJ/mol, which shows that the title compound is a stable compound. The detonation velocity and pressure were evaluated by using Kamlet-Jacobs equations based on the theoretical density and condensed HOF. The crystal structure obtained by molec-ular mechanics belongs to P21 space group, with lattice parameters Z=2, a=13.8017 A, b=13.4072 A, c=5.5635 A.展开更多
基金supported by the National Natural Science Foundation of China(Nos.51375184 and 51605172)the Fundamental Research Funds for the Central Universities(No.2015MS014)
文摘This paper focuses on the buckling behaviors of a micro-scaled bi-directional functionally graded （FG） beam with a rectangular cross-section, which is now widely used in fabricating components of micro-nano-electro-mechanical systems （MEMS/NEMS） with a wide range of aspect ratios. Based on the modified couple stress theory and the principle of minimum potential energy, the governing equations and boundary conditions for a micro-structure-dependent beam theory are derived. The present beam theory incorporates different kinds of higher-order shear assumptions as well as the two familiar beam theories, namely, the Euler-Bernoulli and Timoshenko beam theories. A numerical solu- tion procedure, based on a generalized differential quadrature method （GDQM）, is used to calculate the results of the bi-directional FG beams. The effects of the two exponential FG indexes, the higher-order shear deformations, the length scale parameter, the geomet- ric dimensions, and the different boundary conditions on the critical buckling loads are studied in detail, by assuming that Young＇s modulus obeys an exponential distribution function in both length and thickness directions. To reach the desired critical buckling load, the appropriate exponential FG indexes and geometric shape of micro-beams can be designed according to the proposed theory.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.50971101 and 51074127)the Research Fund of the State Key Laboratory of Solidification Processing(NPU)of China(Grant No.SKLSP201010)
文摘We present a variational density-functional perturbation theory （DFPT） to investigate the lattice dynamics and vibra- tional properties of single crystal bismuth telluride material. The phonon dispersion curves and phonon density of states （DOS） of the material were obtained. The phonon dispersions are divided into two fields by a phonon gap. In the lower field, atomic vibrations of both Bi and Te contribute to the DOS. In the higher field, most contributions come from Te atoms. The calculated Born effective charges and dielectric constants reveal a great anisotropy in the crystal. The largest Born effective charge generates a significant dynamic charge transferring along the c axis. By DFPT calculation, the greatest LO-TO splitting takes place in the infrared phonon modes and reaches 1.7 THz in the Brillouin zone center. The Raman spectra and peaks corresponding to respective atomic vibration modes were found to be in good agreement with the experimental data.
文摘Based on the difficulties of polysemy in translation,this paper explains the rationality of prototype category theory in polysemy translation.Taking Li Zhaoguo’s English version of Su Wen as the research object,it analyzes the polysemy translation of“Jing”,“Zong”,and“Jiu”as examples,and puts forward the translation strategies of polysemy under the guidance of prototype category theory:equivalent substitution between categories,synonymous conversion between categories,transliteration and introspection outside categories,so as to provide reference for the study of polysemy in English translation of texts on traditional Chinese medicine.
基金Supported by the National Natural Science Foundation of China(No.20473029)the Open Project Program of the Key Labora-tory for Supramolecular Structure and Materials of Ministry of EducationJilin University and the Fund for Doctor of Yantai University.
文摘The optimized molecular structure and harmonic vibrational frequencies of a 1,4-bis [ 2-（4-pyridyl）ethenyl]- benzene（BPENB） molecule were calculated via five popular density functional theory（DFI＇） methods. On the basis of the comparison between calculated and experimental results, it is concluded that the B3PW91 and B3LYP methods are superior to the others in optimizing structures, and the BPW91 method reproduces the observed fundamental fre-quencies most satisfactorily.
文摘橡胶材料因具有良好的抗震、吸能作用,在实际工程中应用广泛.然而橡胶超弹性材料的碰撞属于强非线性问题,分析橡胶材料的接触碰撞和大变形问题对于提高装置的缓冲性能具有重要意义.光滑有限元法(smoothed finite element method,S-FEM)是一种弱形式的数值计算方法,相比于传统的有限元方法,光滑有限元法对网格的质量要求不高,允许单元在计算过程中发生较大的变形,且光滑域的构造比较灵活,在不增加自由度的前提下,可以达到较高的精度.在光滑有限元法的基础上,采用双势方法进行接触计算,以充分利用光滑有限元法计算大变形问题的优点和双势方法求解接触力的优势.通过与有限元软件MSC.Marc的数值结果对比,验证了该算法的准确性和能量守恒性,并且分析了摩擦因数对碰撞体的影响.
基金ACKNOWLEDGMENTS This work was supported by the Key Project of Henan Educational Committee （No.12A140004）, China Postdoctoral Science Foundation （No.2013M531361）, and Jiangsu Planned Projects for Postdoctoral Research Funds （No.1201015B）.
文摘Based on the full optimized molecular geometric structures via B3LYP/6-311＋G（2d,p） method, a new gem-dinitro energetic plasticizer, bis（2,2-dinitropropyl ethylene）formal was investigated in order to search for high-performance energetic material. IR spectrum, heat of formation, and detonation performances were predicted. The bond dissociation energies and bond orders for the weakest bonds were analyzed to investigate the thermal stability of the title compound. The results show that the four N-NO2 BDEs are nearly equal to the values of 164.38 kJ/mol, which shows that the title compound is a stable compound. The detonation velocity and pressure were evaluated by using Kamlet-Jacobs equations based on the theoretical density and condensed HOF. The crystal structure obtained by molec-ular mechanics belongs to P21 space group, with lattice parameters Z=2, a=13.8017 A, b=13.4072 A, c=5.5635 A.
