It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mec...It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min^(-1), 50 mm·min^(-1), 100 mm·min^(-1) and 300 mm·min^(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R^2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%^(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min^(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min^(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide.展开更多
The communications industrial standard YD/T 1885-2009 provides the types of headset interfaces, the performance requirements and test methods. Since the release of this standard, more and more manufacturers have adopt...The communications industrial standard YD/T 1885-2009 provides the types of headset interfaces, the performance requirements and test methods. Since the release of this standard, more and more manufacturers have adopted the concentric connector, which gives more choices to consumers and also has benefits on the environmental protection and the healthy development of the mobile terminal industry. Now, the universal headset interface has been included in the draft ITU-T recommendation P.381. lts internationalization will further enhance the universality of the mobile phone headset interlace. It is China＇s another great contribution to the international standardization following the standard of universal power adapter for mobile phones.展开更多
Steel plates are widely used in various structures, such as the deck and bodies of ships and bridges, and in the aerospace industry. In many instances, these plates are subjected to axial compression loads that predis...Steel plates are widely used in various structures, such as the deck and bodies of ships and bridges, and in the aerospace industry. In many instances, these plates are subjected to axial compression loads that predispose the sheets to instability and buckling. In this study, we investigate the buckling and post-buckling behaviors of steel plates having groove-shaped cutouts of various dimensions and angles using finite element method (FEM) (by ABAQUS software) and experimental tests (by an Instron servohydraulic machine). Boundary conditions were clamped by supports at upper and lower ends and free supports at the other edges. The results of both numerical and experimental analyses are compared, which show a very good agreement between them. Finally, based on the experimental findings, formulas are presented for the determination of the buckling load of such plates.展开更多
By applying two nonlinear Granger causality testing methods and rolling window strategy to explore the relationship between speculative activities and crude oil prices, the unidirectional Granger causality from specul...By applying two nonlinear Granger causality testing methods and rolling window strategy to explore the relationship between speculative activities and crude oil prices, the unidirectional Granger causality from speculative activities to returns of crude oil prices during the high price phase is discovered. It is proved that speculative activities did contribute to high crude oil prices after the Asian financial crisis and OPEC＇s output cut in 1998. The unidirectional Granger causality from returns of crude oil prices to speculative activities is significant in general. But after 2000, with the sharp rise in crude oil prices, this unidirectional Granger causality became a complex nonlinear relationship, which cannot be detected by any linear Granger causaIity test.展开更多
基金supported by the Fundamental Research Funds for the Central Universities(No.YX2010-20)the Open Projects Foundation of Key Laboratory of Soil and Water Conservation & Desertification Combat (Beijing ForestryUniversity), Ministry of Education of P.R. China (No.201002) the National Natural Science Foundation of China (No. 31570708, No.30901162)
文摘It is important to quantify the effect of the root diameter, the embedment length of the root and load speed on the soil-root interface mechanical properties for studying the root anchorage. The soilroot interface mechanical properties can be obtained through the pullout force and root slippage curve(F-S curve). About 120 Pinus tabulaeformis single roots whose diameters ranged from 1 mm to 10 mm divided into 6 groups based on different root embedment length(50 mm, 100 mm and 150 mm) and different load velocity(10 mm·min^(-1), 50 mm·min^(-1), 100 mm·min^(-1) and 300 mm·min^(-1)) were investigated using the pullout method. This study aims to explore the mechanical properties of the soil-root interface in the real conditions using the pullout test method. The results showed two kinds of pullout test failure modes during the experimental process: breakage failure and pullout failure. The results showed that the roots were easier to be broken when the root diameter was smaller or the loading speed was larger. The relationship between the maximum anchorage force and root diameter was linear and the linearly dependent coefficient(R^2) was larger than 0.85. The anchorage force increased with the root embedment length. An increase of 10%^(-1)5% for the maximumanchorage force was found when load speed increased from 10 to 300 mm.min^(-1). The mean peak slippage of the root was from 13.81 to 35.79 mm when the load velocity varied from 10 to 300 mm.min^(-1). The study will be helpful for the design of slopes reinforced by vegetation and in predicting risk of uprooting of trees, and will have practical benefits for understanding the mechanism of landslide.
文摘The communications industrial standard YD/T 1885-2009 provides the types of headset interfaces, the performance requirements and test methods. Since the release of this standard, more and more manufacturers have adopted the concentric connector, which gives more choices to consumers and also has benefits on the environmental protection and the healthy development of the mobile terminal industry. Now, the universal headset interface has been included in the draft ITU-T recommendation P.381. lts internationalization will further enhance the universality of the mobile phone headset interlace. It is China＇s another great contribution to the international standardization following the standard of universal power adapter for mobile phones.
文摘Steel plates are widely used in various structures, such as the deck and bodies of ships and bridges, and in the aerospace industry. In many instances, these plates are subjected to axial compression loads that predispose the sheets to instability and buckling. In this study, we investigate the buckling and post-buckling behaviors of steel plates having groove-shaped cutouts of various dimensions and angles using finite element method (FEM) (by ABAQUS software) and experimental tests (by an Instron servohydraulic machine). Boundary conditions were clamped by supports at upper and lower ends and free supports at the other edges. The results of both numerical and experimental analyses are compared, which show a very good agreement between them. Finally, based on the experimental findings, formulas are presented for the determination of the buckling load of such plates.
基金supported by the National Natural Science Foundation of China
文摘By applying two nonlinear Granger causality testing methods and rolling window strategy to explore the relationship between speculative activities and crude oil prices, the unidirectional Granger causality from speculative activities to returns of crude oil prices during the high price phase is discovered. It is proved that speculative activities did contribute to high crude oil prices after the Asian financial crisis and OPEC＇s output cut in 1998. The unidirectional Granger causality from returns of crude oil prices to speculative activities is significant in general. But after 2000, with the sharp rise in crude oil prices, this unidirectional Granger causality became a complex nonlinear relationship, which cannot be detected by any linear Granger causaIity test.
