SiC nanowires/pyrocarbon(SiCnws/PyC)core-shell structure toughenedC/C-ZrC-SiC composites were fabricated by CLVD process,and the influences of PyC shell thickness on the microstructure and ablation resistance of the c...SiC nanowires/pyrocarbon(SiCnws/PyC)core-shell structure toughenedC/C-ZrC-SiC composites were fabricated by CLVD process,and the influences of PyC shell thickness on the microstructure and ablation resistance of the composites were researched.The results presented that SiCnws/PyC core-shell structure had a linear shape,and the composites became dense with the increasing PyC thickness.When the thickness of PyC shell increased from 0 to 2.4μm,the density and thermal conductivity of the composites was improved gradually,but the coefficient of thermal expansion(CTE)decreased firstly and then increased.After the ablation test for 90 s,the ablation rates of the composites decreased continuously as the PyC thickness increased from 0 to 1.4μm,but increased when the PyC thickness was up to 2.4μm.Especially when the PyC thickness was 1.4μm,the linear and mass ablation rates of the composites were 71.25%and 63.01%lower than those of the composites without PyC shell.The reasons behind the remarkable improvement of anti-ablation property were that the proper PyC thickness could alleviate the CTE mismatch to promote the formation of complete oxide coating,improve the thermal conductivity to reduce heat corrosion and enhance the capability to limit the mechanical erosion.展开更多
The generation mechanism of Lg wave from underground nuclear explosion is still not clear at present. The gen-eral viewpoint is that the S wave generated by the near-source scattering of explosion-generated Rg appears...The generation mechanism of Lg wave from underground nuclear explosion is still not clear at present. The gen-eral viewpoint is that the S wave generated by the near-source scattering of explosion-generated Rg appears to be the primary contributor to the low-frequency Lg (0.2~2.0 Hz) from nuclear explosions. The viewpoint is supported by the analysis of regional data from several Yucca Flats, NTS explosions by Patton and Taylor (1995), who fur-ther indicated that the prominent low-frequency spectral null in Lg is due to Rg from a compensated linear vector dipole (CLVD) source. In the paper, the data from Kazakstan Test Sites are investigated by a spectral ratio method. We have found that the spectral ratio of Lg waves is characterized by a spectral scalloping and a pronounced null, and the spectral null does not shift with spall dwell times, showing a strong dependence on shot depth and a very good agreement with those expected from Rg due to a CLVD source.展开更多
利用谱元算法数值模拟了不同地表起伏模型下的补偿线性矢量偶极(Compensated Linear Vector Dipole,CLVD)源Rg波低谷点的特征及相应的震源深度.结果表明,源区地表存在一定起伏情况下,Rg波低谷点依然存在,低谷点位置反映了源区地表起伏...利用谱元算法数值模拟了不同地表起伏模型下的补偿线性矢量偶极(Compensated Linear Vector Dipole,CLVD)源Rg波低谷点的特征及相应的震源深度.结果表明,源区地表存在一定起伏情况下,Rg波低谷点依然存在,低谷点位置反映了源区地表起伏的信息,但与理论值仍有一定偏差.Rg波低谷点受远区地表起伏影响较小.展开更多
基金financial support of the project from the National Natural Science Foundation of China(No.51821091 and 51872233)the Research Foundation of Chengdu University of Technology(No.10912-KYQD202008264)。
文摘SiC nanowires/pyrocarbon(SiCnws/PyC)core-shell structure toughenedC/C-ZrC-SiC composites were fabricated by CLVD process,and the influences of PyC shell thickness on the microstructure and ablation resistance of the composites were researched.The results presented that SiCnws/PyC core-shell structure had a linear shape,and the composites became dense with the increasing PyC thickness.When the thickness of PyC shell increased from 0 to 2.4μm,the density and thermal conductivity of the composites was improved gradually,but the coefficient of thermal expansion(CTE)decreased firstly and then increased.After the ablation test for 90 s,the ablation rates of the composites decreased continuously as the PyC thickness increased from 0 to 1.4μm,but increased when the PyC thickness was up to 2.4μm.Especially when the PyC thickness was 1.4μm,the linear and mass ablation rates of the composites were 71.25%and 63.01%lower than those of the composites without PyC shell.The reasons behind the remarkable improvement of anti-ablation property were that the proper PyC thickness could alleviate the CTE mismatch to promote the formation of complete oxide coating,improve the thermal conductivity to reduce heat corrosion and enhance the capability to limit the mechanical erosion.
基金National Natural Science Foundation of China (40134010).
文摘The generation mechanism of Lg wave from underground nuclear explosion is still not clear at present. The gen-eral viewpoint is that the S wave generated by the near-source scattering of explosion-generated Rg appears to be the primary contributor to the low-frequency Lg (0.2~2.0 Hz) from nuclear explosions. The viewpoint is supported by the analysis of regional data from several Yucca Flats, NTS explosions by Patton and Taylor (1995), who fur-ther indicated that the prominent low-frequency spectral null in Lg is due to Rg from a compensated linear vector dipole (CLVD) source. In the paper, the data from Kazakstan Test Sites are investigated by a spectral ratio method. We have found that the spectral ratio of Lg waves is characterized by a spectral scalloping and a pronounced null, and the spectral null does not shift with spall dwell times, showing a strong dependence on shot depth and a very good agreement with those expected from Rg due to a CLVD source.
文摘利用谱元算法数值模拟了不同地表起伏模型下的补偿线性矢量偶极(Compensated Linear Vector Dipole,CLVD)源Rg波低谷点的特征及相应的震源深度.结果表明,源区地表存在一定起伏情况下,Rg波低谷点依然存在,低谷点位置反映了源区地表起伏的信息,但与理论值仍有一定偏差.Rg波低谷点受远区地表起伏影响较小.