To understand the effects of leaf physiological and morphological characteristics on δ13C of alpine trees, we examined leaf δ13C value, LA, SD, LNC, LPC, LKC, Chla+b, LDMC, LMA and Narea in one-year-old needles of P...To understand the effects of leaf physiological and morphological characteristics on δ13C of alpine trees, we examined leaf δ13C value, LA, SD, LNC, LPC, LKC, Chla+b, LDMC, LMA and Narea in one-year-old needles of Picea schrenkiana var. tianschanica at ten points along an altitudinal gradient from 1420 m to 2300 m a.s.l. on the northern slopes of the Tianshan Mountains in northwest China. Our results indicated that all the leaf traits differed significantly among sampling sites along the altitudinal gradient(P<0.001). LA, SD, LPC, LKC increased linearly with increasing elevation, whereas leaf δ13C, LNC, Chla+b, LDMC, LMA and Narea varied non-linearly with changes in altitude. Stepwise multiple regression analyses showed that four controlled physiological and morphological characteristics influenced the variation of δ13C. Among these four controlled factors, LKC was the most profound physiological factor that affected δ13C values, LA was the secondary morphological factor, SD was the third morphological factor, LNC was the last physiological factor. This suggested that leaf δ13C was directly controlled by physiological and morphological adjustments with changing environmental conditions due to the elevation.展开更多
Shapes are important clues for the identification of ancient ceramics.In this study,digital extraction methods of shape characterization were discussed,using samples of flared mouthed porcelain bowls produced in Jingd...Shapes are important clues for the identification of ancient ceramics.In this study,digital extraction methods of shape characterization were discussed,using samples of flared mouthed porcelain bowls produced in Jingdezhen Hutian Kiln from the Five Dynasties to the Song and Yuan period.By employing the techniques of image enhancement,edge detection and curve fitting of Matlab,the method using digital shape characterization has advanced accuracy and effectiveness of traditional identification which is based on visual and tactual inspections.Together with the increasingly applied compositional data analysis and thermoluminescence dating technique,the method will further improve and upgrade the scientific identification system for ancient ceramics.展开更多
The geometric shapes of specimens are important in impact tensile tests because geometric shapes determine the stress states of the specimens, and precise geometric shapes can obtain proper material properties without...The geometric shapes of specimens are important in impact tensile tests because geometric shapes determine the stress states of the specimens, and precise geometric shapes can obtain proper material properties without non-material factors. The aim of this study was to investigate the 1D form of the stress by changing the length-to-diameter (L/D) ratios of specimens. The experiments were carried out on a split Hopkinson tensile bar (SHTB)-rotating disk indirect bar-bar tensile impact apparatus. The L/D ratios of the LY12CZ specimens used in the test ranged from 1 to 5. Results show that the specimens can be used to obtain exact parameters of materials under the proposed conditions when the L/D ratio is greater than 2. This is because the longer length will reduce or eliminate the effects of the interfaces.展开更多
基金supported by the Major Research Plan of the National Natural Science Foundation of China (Grant No. Y411381001)the National Natural Science Foundation of China (Grant No. 91125025)the Postdoctoral Science Foundation of China (Grant No. 2013M532096)
文摘To understand the effects of leaf physiological and morphological characteristics on δ13C of alpine trees, we examined leaf δ13C value, LA, SD, LNC, LPC, LKC, Chla+b, LDMC, LMA and Narea in one-year-old needles of Picea schrenkiana var. tianschanica at ten points along an altitudinal gradient from 1420 m to 2300 m a.s.l. on the northern slopes of the Tianshan Mountains in northwest China. Our results indicated that all the leaf traits differed significantly among sampling sites along the altitudinal gradient(P<0.001). LA, SD, LPC, LKC increased linearly with increasing elevation, whereas leaf δ13C, LNC, Chla+b, LDMC, LMA and Narea varied non-linearly with changes in altitude. Stepwise multiple regression analyses showed that four controlled physiological and morphological characteristics influenced the variation of δ13C. Among these four controlled factors, LKC was the most profound physiological factor that affected δ13C values, LA was the secondary morphological factor, SD was the third morphological factor, LNC was the last physiological factor. This suggested that leaf δ13C was directly controlled by physiological and morphological adjustments with changing environmental conditions due to the elevation.
基金supported by the National Natural Science Foundation of China (Grant Nos. 50962008,51162017)the Ministry of Education of China in Humanities and Social Sciences Research (Grant No.10YJC780013)
文摘Shapes are important clues for the identification of ancient ceramics.In this study,digital extraction methods of shape characterization were discussed,using samples of flared mouthed porcelain bowls produced in Jingdezhen Hutian Kiln from the Five Dynasties to the Song and Yuan period.By employing the techniques of image enhancement,edge detection and curve fitting of Matlab,the method using digital shape characterization has advanced accuracy and effectiveness of traditional identification which is based on visual and tactual inspections.Together with the increasingly applied compositional data analysis and thermoluminescence dating technique,the method will further improve and upgrade the scientific identification system for ancient ceramics.
文摘The geometric shapes of specimens are important in impact tensile tests because geometric shapes determine the stress states of the specimens, and precise geometric shapes can obtain proper material properties without non-material factors. The aim of this study was to investigate the 1D form of the stress by changing the length-to-diameter (L/D) ratios of specimens. The experiments were carried out on a split Hopkinson tensile bar (SHTB)-rotating disk indirect bar-bar tensile impact apparatus. The L/D ratios of the LY12CZ specimens used in the test ranged from 1 to 5. Results show that the specimens can be used to obtain exact parameters of materials under the proposed conditions when the L/D ratio is greater than 2. This is because the longer length will reduce or eliminate the effects of the interfaces.
