This work investigates the potential of combining hardness gradient with surface texture （an example of bionic coupling） to improve anti-wear properties. The bionic coupling of hardness gradient and Hexagonal Textu...This work investigates the potential of combining hardness gradient with surface texture （an example of bionic coupling） to improve anti-wear properties. The bionic coupling of hardness gradient and Hexagonal Texture （HT） was achieved by laser heat treatment on steel specimens with pre-engraved hexagonal surface texture. The successful establishment of decreasing hardness from surface to internal bulk was verified by hardness measurements along the depth of cross-sectioned specimens and corre- lated with the observations from metallurgical microscopy. The tribological performance of bionic coupling specimens （HT-L） was examined under dry contact condition, together with respective control specimens of individual bionic features, e.g. HT-H （of similar surface hardness generated by conventional heat treatment but without hardness gradient） and SS-L （of smooth surface treated by the same laser processing as for HT-L）. It is found that HT-L not only exhibits lower friction coefficient and less friction fluctuation than HT-H and SS-L, but also demonstrates a 〉50% reduction of wear loss compared to HT-H and SS-L （0.0343 g for HT-L vs. 0.0723 g for HT-H, P〈0.001; 0.0343 g for HT-L vs. 0.0817 g for SS-L, P〈0.001）. Corroboratively, observations with scanning electron microscopy revealed a relatively smooth surface for worn HT-L specimen, contrasting with the rugged and grooved surfaces of worn HT-H and SS-L specimens. These results indicate that the bionic coupling of hardness gradient to hexagonal texture can indeed improve anti-wear properties, affording a new strategy to wear and friction manage- ment.展开更多
Rainfall intensity and slope gradient are two of the most important factors affecting the variations of runoff nitrogen(N).However,the effects of slope gradient and rainfall intensity on N loss via surface flow and in...Rainfall intensity and slope gradient are two of the most important factors affecting the variations of runoff nitrogen(N).However,the effects of slope gradient and rainfall intensity on N loss via surface flow and interflow on weathered granite slopes are poorly understood.In this study,12 artificial rainfalls(three rainfall intensities and four slope gradients)were simulated to investigate the coupling loss characteristics of surface flow–interflow–total nitrogen(TN),nitrate nitrogen(NO_3^--N)and ammonia nitrogen(NH_4^+-N)on weathered granite slopes.The results show that slope gradient has a greater impact on the surface flow when the rainfall intensity is relatively large.The effect gradually weakens with the decrement of rainfall intensity.The interflow yield increases firstly with the prolongation of rainfall duration,then tends to be stable and finally decreases.The total surface flow percentage increases with rainfall intensity while it decreases with increasing slope gradient with a range of 10.88%-71.47%.The TN loss concentration of the surface flow continually decreases with rainfall duration while that of the interflow shows different fluctuations.However,the TN loss loads of both surface flow and interflow increase with increasing rainfall intensity and slope gradient.The NO_3^--N concentration of interflow is much higher than that of the surface flow.The NH_4^+-N concentration is always less than that of NO_3^--N with no significant difference between surface flow and interflow.The percentages of the TN,NO_3^--N,and NH_4^+-N total loss load and concentration of surface flow and interflow were analyzed.The results show that N loss via both surface flow and interflow occurs mainly in the form of NO_3^--N.Most of the N loss is caused by interflow which is the preferential path of runoff nutrient loss.These findings provide data support and underlying insights for the control of runoff and N loss on the weathered granite slopes.展开更多
The NCEP/NCAR reanalysis data are used tostudy the relationships among the change in the tilting of theridgeline surface of the subtropical anticyclone, the estab-lishment of the so-called "seasonal transition ax...The NCEP/NCAR reanalysis data are used tostudy the relationships among the change in the tilting of theridgeline surface of the subtropical anticyclone, the estab-lishment of the so-called "seasonal transition axis (STA)" andthe onset of the Asian summer monsoon. It is shown that themonsoon onset is characterized by the overturning of themeridional temperature gradient (MTG) in the vicinity of theridgeline surface. A MTG index is then constructed to inves-tigate the predictability of the Asian summer monsoon onsetconceptually. Data diagnoses show that if the initial MTG isknown and the meridional gradient across the ridgeline sur-face of the local temperature tendency can be estimated, alate or early onset of the summer monsoon can be qualita-tively predicted in advance.展开更多
Surface wettability is important to design biointerfaces and fimctional biomaterials in various biological applications. However, to date, it remains some confusions about how cells would response to the surfaces with...Surface wettability is important to design biointerfaces and fimctional biomaterials in various biological applications. However, to date, it remains some confusions about how cells would response to the surfaces with different wettabilities. Herein, we systematically explore the adhesive spectra of cells to the surface with wettability gradient from superhydrophilicity to superhydrophobicity, clarifying the effect of wettability on cell adhesion. We envision that this study may provide valuable information for the design of biomedical implants with controllable cell adhesion, such as neural interface devices and flexible implant.展开更多
基金This work was supported by National Natural Science Foundation of China （51375204）, Jilin Provin- cial Science ＆ Technology Department （20140101056JC）, and Project ＂985＂ on Engineering Bionics of Jilin University. We thank Prof. Yan Shi and Dr. Jia Liu from Changchun University of Science and Technology for their help on laser heat treatment.
文摘This work investigates the potential of combining hardness gradient with surface texture （an example of bionic coupling） to improve anti-wear properties. The bionic coupling of hardness gradient and Hexagonal Texture （HT） was achieved by laser heat treatment on steel specimens with pre-engraved hexagonal surface texture. The successful establishment of decreasing hardness from surface to internal bulk was verified by hardness measurements along the depth of cross-sectioned specimens and corre- lated with the observations from metallurgical microscopy. The tribological performance of bionic coupling specimens （HT-L） was examined under dry contact condition, together with respective control specimens of individual bionic features, e.g. HT-H （of similar surface hardness generated by conventional heat treatment but without hardness gradient） and SS-L （of smooth surface treated by the same laser processing as for HT-L）. It is found that HT-L not only exhibits lower friction coefficient and less friction fluctuation than HT-H and SS-L, but also demonstrates a 〉50% reduction of wear loss compared to HT-H and SS-L （0.0343 g for HT-L vs. 0.0723 g for HT-H, P〈0.001; 0.0343 g for HT-L vs. 0.0817 g for SS-L, P〈0.001）. Corroboratively, observations with scanning electron microscopy revealed a relatively smooth surface for worn HT-L specimen, contrasting with the rugged and grooved surfaces of worn HT-H and SS-L specimens. These results indicate that the bionic coupling of hardness gradient to hexagonal texture can indeed improve anti-wear properties, affording a new strategy to wear and friction manage- ment.
基金supported by the National Natural Science Foundation of China (4187706541471221)
文摘Rainfall intensity and slope gradient are two of the most important factors affecting the variations of runoff nitrogen(N).However,the effects of slope gradient and rainfall intensity on N loss via surface flow and interflow on weathered granite slopes are poorly understood.In this study,12 artificial rainfalls(three rainfall intensities and four slope gradients)were simulated to investigate the coupling loss characteristics of surface flow–interflow–total nitrogen(TN),nitrate nitrogen(NO_3^--N)and ammonia nitrogen(NH_4^+-N)on weathered granite slopes.The results show that slope gradient has a greater impact on the surface flow when the rainfall intensity is relatively large.The effect gradually weakens with the decrement of rainfall intensity.The interflow yield increases firstly with the prolongation of rainfall duration,then tends to be stable and finally decreases.The total surface flow percentage increases with rainfall intensity while it decreases with increasing slope gradient with a range of 10.88%-71.47%.The TN loss concentration of the surface flow continually decreases with rainfall duration while that of the interflow shows different fluctuations.However,the TN loss loads of both surface flow and interflow increase with increasing rainfall intensity and slope gradient.The NO_3^--N concentration of interflow is much higher than that of the surface flow.The NH_4^+-N concentration is always less than that of NO_3^--N with no significant difference between surface flow and interflow.The percentages of the TN,NO_3^--N,and NH_4^+-N total loss load and concentration of surface flow and interflow were analyzed.The results show that N loss via both surface flow and interflow occurs mainly in the form of NO_3^--N.Most of the N loss is caused by interflow which is the preferential path of runoff nutrient loss.These findings provide data support and underlying insights for the control of runoff and N loss on the weathered granite slopes.
文摘The NCEP/NCAR reanalysis data are used tostudy the relationships among the change in the tilting of theridgeline surface of the subtropical anticyclone, the estab-lishment of the so-called "seasonal transition axis (STA)" andthe onset of the Asian summer monsoon. It is shown that themonsoon onset is characterized by the overturning of themeridional temperature gradient (MTG) in the vicinity of theridgeline surface. A MTG index is then constructed to inves-tigate the predictability of the Asian summer monsoon onsetconceptually. Data diagnoses show that if the initial MTG isknown and the meridional gradient across the ridgeline sur-face of the local temperature tendency can be estimated, alate or early onset of the summer monsoon can be qualita-tively predicted in advance.
基金supported by the National Natural Science Foundation of China(21425314,21501184,21434009,21421061,21504098)the Key Research Program of the Chinese Academy of Sciences(KJZD-EW-M01)+2 种基金Ministry of Science and Technology(2013YQ190467)the Top-Notch Young Talents Program of ChinaBeijing Municipal Science&Technology Commission(Z161100000116037)
文摘Surface wettability is important to design biointerfaces and fimctional biomaterials in various biological applications. However, to date, it remains some confusions about how cells would response to the surfaces with different wettabilities. Herein, we systematically explore the adhesive spectra of cells to the surface with wettability gradient from superhydrophilicity to superhydrophobicity, clarifying the effect of wettability on cell adhesion. We envision that this study may provide valuable information for the design of biomedical implants with controllable cell adhesion, such as neural interface devices and flexible implant.
