Well-sintered polycrystalline cubic boron nitride(PCBN)composites with different contents of cubic boron nitride(CBN) were obtained using Al and TiN as additives under pressure of 5.5 GPa and temperature of 1450 ℃.Th...Well-sintered polycrystalline cubic boron nitride(PCBN)composites with different contents of cubic boron nitride(CBN) were obtained using Al and TiN as additives under pressure of 5.5 GPa and temperature of 1450 ℃.The network structure of CBN grains and bonding materials was observed using scanning electron microscope(SEM).With the help of X-ray diffraction(XRD) analysis,TiB2 and AlN could be determined as main products and Al3 Ti also was detected in the Al-rich samples after sintering process.Furthermore,it was shown that Vickers hardness of composites was improved with the increase of CBN contents.However,the lifetime of PCBN composites was in negative correlation with the amount of CBN in turning GCr15 hardened steels,and the surface roughness of workpieces machined by these PCBN composites also showed the same trend.A series of cutting data confirmed that the low CBN content in PCBN composites could enhance the working durability and improve the surface quality in turning hardened steels.The present experiments also indicated that the lowest value of flank wear was not constant for different PCBN composites when they were used to machine several workpieces with different hardness.展开更多
目的探讨致密斑点型抗核抗体(dense fine speckled,DFS)在抗核抗体(antinuclear antibody,ANA)中的检出率及其在类风湿关节炎(rheumatoid arthritis,RA)患者中的临床价值。方法回顾性分析2017年至2020年本院就诊患者7865例ANA检测标本,...目的探讨致密斑点型抗核抗体(dense fine speckled,DFS)在抗核抗体(antinuclear antibody,ANA)中的检出率及其在类风湿关节炎(rheumatoid arthritis,RA)患者中的临床价值。方法回顾性分析2017年至2020年本院就诊患者7865例ANA检测标本,采用间接免疫荧光法(indirect immunofluorescence,IIF),统计DFS在ANA中的阳性率及风湿免疫科ANA、DFS的阳性率。结果7865例ANA检测标本中阳性检出率为34.01%(2675/7865),DFS检测率为2.75%(216/7865),DFS占ANA阳性标本的8.07%(216/2675)。ANA阳性标本中男性占18.62%(498/2675),女性占81.38%(2177/2675),DFS阳性标本中男性占29.17%(63/216),女性占70.83%(153/216),男女间DFS差异有统计学意义(P<0.01)。DFS患者中风湿免疫科占52.78%(114/216),114人中有38人已确诊为类风湿性关节炎,占总的DFS阳性比率为17.59%。结论DFS是ANA阳性荧光模型中常见的一种,归属于细胞核核型中的斑点型,其中类风湿关节炎患者占有较高的比率。展开更多
Color centers of CaF2 crystals subjected to three high-dose gamma-ray irradiation treatments were studied. Three absorption bands at 349, 409 and 478 nm are ascribed to the F interstitials through the variation in dif...Color centers of CaF2 crystals subjected to three high-dose gamma-ray irradiation treatments were studied. Three absorption bands at 349, 409 and 478 nm are ascribed to the F interstitials through the variation in difference additional absorption values. The transformation of interstitial F atoms to F ions (Fi-) is demonstrated using data with increasing radiation dose. The decrease in the 600 nm absorption band and the occurrence of the 580 nm band correspond to F2+ center conversion to F center. The complex (F^--Fi0 ) might be associated with the 962 and 1196 nm bands.展开更多
Color center concentrations of the Al2O3 crystal grown by temperature gradient techniques were calculated from Gaussian fits to absorption spectra. The concentrations for F- and F + -centers at 204, 232, and 255 nm we...Color center concentrations of the Al2O3 crystal grown by temperature gradient techniques were calculated from Gaussian fits to absorption spectra. The concentrations for F- and F + -centers at 204, 232, and 255 nm were determined to be 1.361×10 17 , 0.098×10 17 , and 0.325×10 17cm-3 , respectively. Studies have shown that the thermoluminescence (TL) glow curve exhibits a prominent 450 K peak that matches well the first-order fitting curve. The thermal activation energy E and frequency factor s of the trap were determined to be 0.94456±0.00545 eV and 5.8703×10 11 s-1 . With this theoretical analysis, a simple one-trap/one-center TL model is presented to provide a theoretical explanation of the TL process.展开更多
文摘Well-sintered polycrystalline cubic boron nitride(PCBN)composites with different contents of cubic boron nitride(CBN) were obtained using Al and TiN as additives under pressure of 5.5 GPa and temperature of 1450 ℃.The network structure of CBN grains and bonding materials was observed using scanning electron microscope(SEM).With the help of X-ray diffraction(XRD) analysis,TiB2 and AlN could be determined as main products and Al3 Ti also was detected in the Al-rich samples after sintering process.Furthermore,it was shown that Vickers hardness of composites was improved with the increase of CBN contents.However,the lifetime of PCBN composites was in negative correlation with the amount of CBN in turning GCr15 hardened steels,and the surface roughness of workpieces machined by these PCBN composites also showed the same trend.A series of cutting data confirmed that the low CBN content in PCBN composites could enhance the working durability and improve the surface quality in turning hardened steels.The present experiments also indicated that the lowest value of flank wear was not constant for different PCBN composites when they were used to machine several workpieces with different hardness.
文摘Color centers of CaF2 crystals subjected to three high-dose gamma-ray irradiation treatments were studied. Three absorption bands at 349, 409 and 478 nm are ascribed to the F interstitials through the variation in difference additional absorption values. The transformation of interstitial F atoms to F ions (Fi-) is demonstrated using data with increasing radiation dose. The decrease in the 600 nm absorption band and the occurrence of the 580 nm band correspond to F2+ center conversion to F center. The complex (F^--Fi0 ) might be associated with the 962 and 1196 nm bands.
文摘Color center concentrations of the Al2O3 crystal grown by temperature gradient techniques were calculated from Gaussian fits to absorption spectra. The concentrations for F- and F + -centers at 204, 232, and 255 nm were determined to be 1.361×10 17 , 0.098×10 17 , and 0.325×10 17cm-3 , respectively. Studies have shown that the thermoluminescence (TL) glow curve exhibits a prominent 450 K peak that matches well the first-order fitting curve. The thermal activation energy E and frequency factor s of the trap were determined to be 0.94456±0.00545 eV and 5.8703×10 11 s-1 . With this theoretical analysis, a simple one-trap/one-center TL model is presented to provide a theoretical explanation of the TL process.
