Guided elastic waves have a great potential in pipe inspection as an efficient and low-cost nondestructive evaluation （NDE） technique, among which the wave of mode L（0, 2） receives a lot of attention because this ...Guided elastic waves have a great potential in pipe inspection as an efficient and low-cost nondestructive evaluation （NDE） technique, among which the wave of mode L（0, 2） receives a lot of attention because this mode is the fastest mode in a weakly dispersive region of frequency to minimize dispersion effects over a long distance and sensitive to the defects distributed circumferentially. Though many experimental and numerical researches have already been carried out about the excitation of L（0, 2） and its interaction with the defect in a hollow cylinder, its excitation mechanism has not been clarified yet. In this paper based on the transient response solution of the hollow cylinder, derived by the method of eigenfunction expansion, the theory about the exciting mechanism of mode L（0, 2） is advanced and the effects of the spatial distribution, vibration frequency and direction of the external force on the excitation are discussed. And the pure mode L（0, 2） is excited successfully under the parameters obtained through theoretical analysis. Furthermore, its interactions with some kinds of defects in hollow cylinders are simulated with the method of finite element analysis （FEA） and the results agree well with those obtained by other researchers.展开更多
New Mg2Si based alloy were prepared by mechanical alloying. Sintering temperature was from 825 to 865K, which indicated that few Mg2Si were produced at lower temperature while MgO were produced at higher temperature. ...New Mg2Si based alloy were prepared by mechanical alloying. Sintering temperature was from 825 to 865K, which indicated that few Mg2Si were produced at lower temperature while MgO were produced at higher temperature. Microstructure image showed that at sintering temperature of 855K, Mg2Si were mostly synthesized with the reaction of purity magnesia powder and silicon powder. Hardness and wear tests proved that the new synthetic silicon magnesium alloy had higher hardness and good wear resistance. Under the same testing conditions, it is found that the hardness of the new material is 420.50, and pure magnesium is only 41.65.In the same experiments it is also found that under the same pressure, pure magnesium alloys than silicon wearing capacity of pure magnesium is 2 times as high that of Mg2Si based alloy. It shows that Mg2Si based alloy is the ideal material for the wear parts of car engine cylinder liner because of its small density, stable dimension, high hardness and wear-resisting.展开更多
在国内外的CNG-2型气瓶标准中,型式试验里有一项必不可少的试验项目"环境试验"(或称为"酸环境试验")。与GB 24160-2009、ISO 11439:2000(E)和ECE R 110:2014相比较,ISO11439:2013(E)型式试验对环境试验方法有较大...在国内外的CNG-2型气瓶标准中,型式试验里有一项必不可少的试验项目"环境试验"(或称为"酸环境试验")。与GB 24160-2009、ISO 11439:2000(E)和ECE R 110:2014相比较,ISO11439:2013(E)型式试验对环境试验方法有较大的改变。本文通过研究这几种标准关于环境试验方法的不同之处,分析讨论ISO 11439:2013(E)环境试验方法发生改变的目的和意义,了解到标准制定者对试验的仿真性和实用性的重视,为其他标准的修订起到良好的推进作用。展开更多
CS-CMC bipolar membrane was prepared and the cross-section photograph of CS-CMC BM was observed by SEM. FT-IR spectrum indicated that CS-CMC BM contained -N=CRH2^＋ and -COO^- functional groups. The charge density of ...CS-CMC bipolar membrane was prepared and the cross-section photograph of CS-CMC BM was observed by SEM. FT-IR spectrum indicated that CS-CMC BM contained -N=CRH2^＋ and -COO^- functional groups. The charge density of -N--CRH2^＋ in CS membrane was about 14.13 mmol/g and the charge density of -COO in CMC membrane was about 9.01 mmol/g. The electrochemistry properties of CS-CMC BM were also studied. CS-CMC BM not only can effectively stop FeO4^2- from diffusing into the cathode chamber, but also plays an important role in the supply of OH＂ consumed during the electro-generated FeO4^2- process.展开更多
The dependence of charged particle pseudorapidity distributions on centrality in Pb-Pb collisions at√sNN=2.76 TeV is studied by using a multi-source thermal model(previously the two-cylinder model or the multi-source...The dependence of charged particle pseudorapidity distributions on centrality in Pb-Pb collisions at√sNN=2.76 TeV is studied by using a multi-source thermal model(previously the two-cylinder model or the multi-source ideal gas model).The rapidity shifts of the interacting system are almost independent of the centrality class.The contribution of leading nucleons increases with the increasing centrality class(percent).The calculated results are compared and found to be in agreement with the experimental data of the ATLAS,ALICE,and CMS collaborations.展开更多
文摘Guided elastic waves have a great potential in pipe inspection as an efficient and low-cost nondestructive evaluation （NDE） technique, among which the wave of mode L（0, 2） receives a lot of attention because this mode is the fastest mode in a weakly dispersive region of frequency to minimize dispersion effects over a long distance and sensitive to the defects distributed circumferentially. Though many experimental and numerical researches have already been carried out about the excitation of L（0, 2） and its interaction with the defect in a hollow cylinder, its excitation mechanism has not been clarified yet. In this paper based on the transient response solution of the hollow cylinder, derived by the method of eigenfunction expansion, the theory about the exciting mechanism of mode L（0, 2） is advanced and the effects of the spatial distribution, vibration frequency and direction of the external force on the excitation are discussed. And the pure mode L（0, 2） is excited successfully under the parameters obtained through theoretical analysis. Furthermore, its interactions with some kinds of defects in hollow cylinders are simulated with the method of finite element analysis （FEA） and the results agree well with those obtained by other researchers.
基金Funded by the " 973 " Program of China (No. 2007CB613502)
文摘New Mg2Si based alloy were prepared by mechanical alloying. Sintering temperature was from 825 to 865K, which indicated that few Mg2Si were produced at lower temperature while MgO were produced at higher temperature. Microstructure image showed that at sintering temperature of 855K, Mg2Si were mostly synthesized with the reaction of purity magnesia powder and silicon powder. Hardness and wear tests proved that the new synthetic silicon magnesium alloy had higher hardness and good wear resistance. Under the same testing conditions, it is found that the hardness of the new material is 420.50, and pure magnesium is only 41.65.In the same experiments it is also found that under the same pressure, pure magnesium alloys than silicon wearing capacity of pure magnesium is 2 times as high that of Mg2Si based alloy. It shows that Mg2Si based alloy is the ideal material for the wear parts of car engine cylinder liner because of its small density, stable dimension, high hardness and wear-resisting.
文摘CS-CMC bipolar membrane was prepared and the cross-section photograph of CS-CMC BM was observed by SEM. FT-IR spectrum indicated that CS-CMC BM contained -N=CRH2^＋ and -COO^- functional groups. The charge density of -N--CRH2^＋ in CS membrane was about 14.13 mmol/g and the charge density of -COO in CMC membrane was about 9.01 mmol/g. The electrochemistry properties of CS-CMC BM were also studied. CS-CMC BM not only can effectively stop FeO4^2- from diffusing into the cathode chamber, but also plays an important role in the supply of OH＂ consumed during the electro-generated FeO4^2- process.
基金Supported by the National Natural Science Foundation of China under Grant No 10975095the National Fundamental Fund of Personnel Training under Grant No J1103210the Foundation of Shanxi Scholarship Council of China under Grant No 2012-012.
文摘The dependence of charged particle pseudorapidity distributions on centrality in Pb-Pb collisions at√sNN=2.76 TeV is studied by using a multi-source thermal model(previously the two-cylinder model or the multi-source ideal gas model).The rapidity shifts of the interacting system are almost independent of the centrality class.The contribution of leading nucleons increases with the increasing centrality class(percent).The calculated results are compared and found to be in agreement with the experimental data of the ATLAS,ALICE,and CMS collaborations.
