The microstructure formation and grains refinement of two Mg-based alloys,i.e.AZ31 and AZ91D,were reported using an electromagnetic vibration(EMV) technique.These two alloys were solidified at various vibration freque...The microstructure formation and grains refinement of two Mg-based alloys,i.e.AZ31 and AZ91D,were reported using an electromagnetic vibration(EMV) technique.These two alloys were solidified at various vibration frequencies and the microstructures were observed.The average size of grains was quantitatively measured as a function of vibration frequencies. Moreover,the grain size distribution was outlined versus number fraction.A novel model was proposed to account for the microstructure formation and grain refinement when considering the significant difference of the electrical resistivity properties of the solid and the liquid during EMV processing in the semisolid state.The remarkable difference originates uncoupled movement between the mobile solid and the sluggish liquid,which can activate melt flow.The microstructure evolution can be well explained when the fluid flow intensity versus vibration frequency is taken into account.Moreover,the influence of the static magnetic field on texture formation is also considered,which plays an important role at higher vibration frequencies.展开更多
Present investigation is concerned with the free vibration property of a beam with periodically variable cross-sections.For the special geometry characteristic,the beam was modelled as the combination of long equal-le...Present investigation is concerned with the free vibration property of a beam with periodically variable cross-sections.For the special geometry characteristic,the beam was modelled as the combination of long equal-length uniform Euler-Bernoulli beam segments and short equal-length uniform Timoshenko beam segments alternately.By using continuity conditions,the hybrid beam unit(ETE-B) consisting of Euler-Bernoulli beam,Timoshenko beam and Euler-Bernoulli beam in sequence was developed.Classical boundary conditions of pinned-pinned,clamped-clamped and clamped-free were considered to obtain the natural frequencies.Numerical examples of the equal-length composite beam with 1,2 and 3 ETE-B units were presented and compared with the equal-length and equal-cross-section Euler-Bernoulli beam,respectively.The work demonstrates that natural frequencies of the composite beam are larger than those of the Euler-Bernoulli beam,which in practice,is the interpretation that the inner-welded plate can strengthen a hollow beam.In this work,comparisons with the finite element calculation were presented to validate the ETE-B model.展开更多
Radiofrequency coil is one of the most important components for a nuclear magnetic resonance(NMR)instrument.In this article,some planar micro coils with an inner diameter of 2 mm and number of turns that varied from 1...Radiofrequency coil is one of the most important components for a nuclear magnetic resonance(NMR)instrument.In this article,some planar micro coils with an inner diameter of 2 mm and number of turns that varied from 1 to 11 were investigated based on the printed circuit board(PCB)technology.The electrical characterization of micro coils show that self-resonant frequencies are larger than 200 MHz.Then,an NMR measurement platform with a static magnetic field of 0.66 T was constructed and the signal to noise ratio(SNR)values of the NMR were analyzed.It was found that the SNR is optimal when the turn number of the micro coils is six and the excitation time of a 90°pulse is 0.8?s.Finally,we used the micro coil with six turns to study the transverse relaxation rate of copper sulfate pentahydrate aqueous solution with different concentrations.It was found that the transverse relaxation rate is proportional to the solution concentration.Results from the micro coil were verified by measurements using a Bruker Minispec MQ60.展开更多
Objective: To simplify the TCM pattern of the zang-fu organs. Methods: A database of zang-fu syndromes was established. The relationship between the zang-fu syndromes was analyzed by means of frequency analysis, assoc...Objective: To simplify the TCM pattern of the zang-fu organs. Methods: A database of zang-fu syndromes was established. The relationship between the zang-fu syndromes was analyzed by means of frequency analysis, association rule, and ф-coefficient correlation. Results: The six zang-fu organs of the heart, liver, spleen, lung, kidney, and stomach prove to be the main components of the zang-fu pattern. The large intestine, small intestine, gallbladder, bladder, triple energizer, and pericardium have strong association and positive correlation with the above-mentioned six zang-fu organs, and their clinical symptoms can all be included into the symptoms of these six zang-fu organs. Conclusion: The traditional TCM pattern of six-zang and six-fu can be simplified into five-zang and one-fu.展开更多
文摘The microstructure formation and grains refinement of two Mg-based alloys,i.e.AZ31 and AZ91D,were reported using an electromagnetic vibration(EMV) technique.These two alloys were solidified at various vibration frequencies and the microstructures were observed.The average size of grains was quantitatively measured as a function of vibration frequencies. Moreover,the grain size distribution was outlined versus number fraction.A novel model was proposed to account for the microstructure formation and grain refinement when considering the significant difference of the electrical resistivity properties of the solid and the liquid during EMV processing in the semisolid state.The remarkable difference originates uncoupled movement between the mobile solid and the sluggish liquid,which can activate melt flow.The microstructure evolution can be well explained when the fluid flow intensity versus vibration frequency is taken into account.Moreover,the influence of the static magnetic field on texture formation is also considered,which plays an important role at higher vibration frequencies.
基金Projects(51605138,U1508210)supported by the National Natural Science Foundation of ChinaProject(BK20160286)supported by the Natural Science Foundation of Jiangsu Province,ChinaProject(2015B30214)supported by the Fundamental Research Funds for the Central Universities,China
文摘Present investigation is concerned with the free vibration property of a beam with periodically variable cross-sections.For the special geometry characteristic,the beam was modelled as the combination of long equal-length uniform Euler-Bernoulli beam segments and short equal-length uniform Timoshenko beam segments alternately.By using continuity conditions,the hybrid beam unit(ETE-B) consisting of Euler-Bernoulli beam,Timoshenko beam and Euler-Bernoulli beam in sequence was developed.Classical boundary conditions of pinned-pinned,clamped-clamped and clamped-free were considered to obtain the natural frequencies.Numerical examples of the equal-length composite beam with 1,2 and 3 ETE-B units were presented and compared with the equal-length and equal-cross-section Euler-Bernoulli beam,respectively.The work demonstrates that natural frequencies of the composite beam are larger than those of the Euler-Bernoulli beam,which in practice,is the interpretation that the inner-welded plate can strengthen a hollow beam.In this work,comparisons with the finite element calculation were presented to validate the ETE-B model.
基金supported by the National Natural Science Foundation of China(Grant No.51175083)the Jiangsu Province University Industry Cooperation Innovation Foundation-Prospective Study of China(Grant No.BY 2011135)
文摘Radiofrequency coil is one of the most important components for a nuclear magnetic resonance(NMR)instrument.In this article,some planar micro coils with an inner diameter of 2 mm and number of turns that varied from 1 to 11 were investigated based on the printed circuit board(PCB)technology.The electrical characterization of micro coils show that self-resonant frequencies are larger than 200 MHz.Then,an NMR measurement platform with a static magnetic field of 0.66 T was constructed and the signal to noise ratio(SNR)values of the NMR were analyzed.It was found that the SNR is optimal when the turn number of the micro coils is six and the excitation time of a 90°pulse is 0.8?s.Finally,we used the micro coil with six turns to study the transverse relaxation rate of copper sulfate pentahydrate aqueous solution with different concentrations.It was found that the transverse relaxation rate is proportional to the solution concentration.Results from the micro coil were verified by measurements using a Bruker Minispec MQ60.
基金Supported by the National Fund Supporting Project of Natural Science (No.30772695)National Supporting Plan for Science and Technology in "The 11th Five-year Plan" (No.2006 BAI08B01-05)National Major Special Subject of Science and Technology (No.2009ZX10005-019)
文摘Objective: To simplify the TCM pattern of the zang-fu organs. Methods: A database of zang-fu syndromes was established. The relationship between the zang-fu syndromes was analyzed by means of frequency analysis, association rule, and ф-coefficient correlation. Results: The six zang-fu organs of the heart, liver, spleen, lung, kidney, and stomach prove to be the main components of the zang-fu pattern. The large intestine, small intestine, gallbladder, bladder, triple energizer, and pericardium have strong association and positive correlation with the above-mentioned six zang-fu organs, and their clinical symptoms can all be included into the symptoms of these six zang-fu organs. Conclusion: The traditional TCM pattern of six-zang and six-fu can be simplified into five-zang and one-fu.
