By means of dynamic plastic deformation （DPD） followed by thermal annealing, a mixed structure of micro-sized austenite grains embedded with nano-scale twin bundles （of about 20% in volume） has been synthesized in...By means of dynamic plastic deformation （DPD） followed by thermal annealing, a mixed structure of micro-sized austenite grains embedded with nano-scale twin bundles （of about 20% in volume） has been synthesized in a 316L stainless steel （SS）. Such a 316L SS sample exhibits a tensile strength as high as 1001 MPa and an elongation-to-failure of about 23%. The much elevated strength originates from the presence of a considerable number of strengthening nano-twin bundles, while the ductility from the recrystallized grains. The superior strength-ductility combination achieved in the nano-twins-strengthened austenite steel demonstrates a novel approach for optimizing the mechanical properties in engineering materials.展开更多
Biological tiny structures have been observed on many kinds of surfaces such as lotus leaves,which have an effect on the coloration of Morpho butterflies and enhance the hydrophobicity of natural surfaces.We investiga...Biological tiny structures have been observed on many kinds of surfaces such as lotus leaves,which have an effect on the coloration of Morpho butterflies and enhance the hydrophobicity of natural surfaces.We investigated the micro-scale and nano-scale structures on the wing surfaces of insects and found that the hierarchical multiple roughness structures help in enhancing the hydrophobicity.After examining 10 orders and 24 species of flying Pterygotan insects,we found that micro-scale and nano-scale structures typically exist on both the upper and lower wing surfaces of flying insects.The tiny structures such as denticle or setae on the insect wings enhance the hydrophobicity,thereby enabling the wings to be cleaned more easily.And the hydrophobic insect wings undergo a transition from Cassie to Wenzel states at pitch/size ratio of about 20.In order to examine the wetting characteristics on a rough surface,a biomimetic surface with micro-scale pillars is fabricated on a silicon wafer, which exhibits the same behavior as the insect wing,with the Cassie-Wenzel transition occurring consistently around a pitch/width value of 20.展开更多
In the transformation of methanol to gasoline （MTG）, the selectivity to gasoline and the aromatic content in the produced gasoline are important factors. The catalytic activities of steam-treated and non-steam-treat...In the transformation of methanol to gasoline （MTG）, the selectivity to gasoline and the aromatic content in the produced gasoline are important factors. The catalytic activities of steam-treated and non-steam-treated nano-scale H-ZSM-5 （NHZ5） catalysts impregnated with Ag（I）, Zn（II） or P（V） have been investigated in a continuous flow fixed bed reactor. The NH3-TPD results showed that after impregnation, the Ag/NHZ5, Zn/NHZ5 and P/NHZ5 catalysts contained comparatively more strong, medium-strong and weak acid sites, respectively. Treatment with steam decreased the number of acid sites in all the catalysts, but the pore volumes in the catalysts were larger which improved carbon deposition resistance resulting in prolonged lifetimes. After 6 h of MTG reaction, the selectivity to gasoline for the steam-treated catalysts, Agrho/NHZ5, ZnH2o/NHZ5 and PH2o/NHZ5 were 70.5, 68.4 and 68.7 wt-%, respectively, whereas their respective aromatic contents in the produced gasoline were 61.9, 55.4 and 39.0 wt-%. Thus Pn2o/NHZ5 is the most promising catalyst for MTG applications which can meet the China IV gasoline standard that the amount of aromatics in gasoline should be less than 48 wt-%.展开更多
Atom lithography with chromium can be utilized to fabricate a pitch standard, which is chrectly traceable to me wavelength of the laser standing waves. The result of a calibrated commercial AFM measurement demonstrate...Atom lithography with chromium can be utilized to fabricate a pitch standard, which is chrectly traceable to me wavelength of the laser standing waves. The result of a calibrated commercial AFM measurement demonstrates that the pitch standard is （212.8±0.1） nm with a peak-to-valley-height （PTVH） better than 20 nm. The measurement results show the high period accuracy of traceability with the standing laser wavelength （λ/2 = 212.78 nm）. The Cr nano-grating covers a 1000μm×500 μm area, with a PTVH better than 10 nm. The feature width broadening of the Cr nanostructure has been experimentally observed along the direction of the standing waves. The PTVH along the Gaussian laser direction is similar to a Gaussian distribution. Highly uniform periodic nanostructures with a big area at the millimeter scale, and the surface growth uniformity of the Cr nano-grating, show its great potential in the application of a traceable pitch standard at trans-scales.展开更多
Geogas prospecting is a new method in the search for deep and/or concealed mineral deposits.The probing depth of the method comes to 300-500 m below the surface. The method, based on nuclear aualysis and accumulation ...Geogas prospecting is a new method in the search for deep and/or concealed mineral deposits.The probing depth of the method comes to 300-500 m below the surface. The method, based on nuclear aualysis and accumulation sampling, has matured and become useful method of geogas prospecting, through authors' studies more than 10 years. The study of the mechanism for geogas prospecting has also been progressed. It bas been revealed that the geogas matter is in the form of nano-scale particles of the ores by the observation of scanning electron microscope (SEM). This paper summarizes the feature of the geogas anomaly, and describes its forming mechanism. A new example using geogas prospecting is given.展开更多
There are two main trends in the development of unmanned aerial vehicle(UAV)technologies:miniaturization and intellectualization,in which realizing object tracking capabilities for a nano-scale UAV is one of the most ...There are two main trends in the development of unmanned aerial vehicle(UAV)technologies:miniaturization and intellectualization,in which realizing object tracking capabilities for a nano-scale UAV is one of the most challenging problems.In this paper,we present a visual object tracking and servoing control system utilizing a tailor-made 38 g nano-scale quadrotor.A lightweight visual module is integrated to enable object tracking capabilities,and a micro positioning deck is mounted to provide accurate pose estimation.In order to be robust against object appearance variations,a novel object tracking algorithm,denoted by RMCTer,is proposed,which integrates a powerful short-term tracking module and an efficient long-term processing module.In particular,the long-term processing module can provide additional object information and modify the short-term tracking model in a timely manner.Furthermore,a positionbased visual servoing control method is proposed for the quadrotor,where an adaptive tracking controller is designed by leveraging backstepping and adaptive techniques.Stable and accurate object tracking is achieved even under disturbances.Experimental results are presented to demonstrate the high accuracy and stability of the whole tracking system.展开更多
基金the National Natural Science Foundation of China (Grants Nos. 50971122, 50431010,50621091 and 50890171)the Ministry of Science and Technology of China (2005CB623604) are acknowledged
文摘By means of dynamic plastic deformation （DPD） followed by thermal annealing, a mixed structure of micro-sized austenite grains embedded with nano-scale twin bundles （of about 20% in volume） has been synthesized in a 316L stainless steel （SS）. Such a 316L SS sample exhibits a tensile strength as high as 1001 MPa and an elongation-to-failure of about 23%. The much elevated strength originates from the presence of a considerable number of strengthening nano-twin bundles, while the ductility from the recrystallized grains. The superior strength-ductility combination achieved in the nano-twins-strengthened austenite steel demonstrates a novel approach for optimizing the mechanical properties in engineering materials.
基金supported by the National Research Laboratory Program, Korea Science and Engineering Foundation Grant (Grant No. R0A-2007-000-20012-0)the Korea Research Foundation Grant (Grant No. KRF-2006-005-J03301)+1 种基金J. Hong was partially supported by the Korea Research Foundation Grant funded by the Korean Government (MOEHRD) (Grant No. KRP-2006-214-D00056)J. R. Lukes acknowledges partial support from the National Science Foundation (Grant No.CBET-0424101)
文摘Biological tiny structures have been observed on many kinds of surfaces such as lotus leaves,which have an effect on the coloration of Morpho butterflies and enhance the hydrophobicity of natural surfaces.We investigated the micro-scale and nano-scale structures on the wing surfaces of insects and found that the hierarchical multiple roughness structures help in enhancing the hydrophobicity.After examining 10 orders and 24 species of flying Pterygotan insects,we found that micro-scale and nano-scale structures typically exist on both the upper and lower wing surfaces of flying insects.The tiny structures such as denticle or setae on the insect wings enhance the hydrophobicity,thereby enabling the wings to be cleaned more easily.And the hydrophobic insect wings undergo a transition from Cassie to Wenzel states at pitch/size ratio of about 20.In order to examine the wetting characteristics on a rough surface,a biomimetic surface with micro-scale pillars is fabricated on a silicon wafer, which exhibits the same behavior as the insect wing,with the Cassie-Wenzel transition occurring consistently around a pitch/width value of 20.
文摘In the transformation of methanol to gasoline （MTG）, the selectivity to gasoline and the aromatic content in the produced gasoline are important factors. The catalytic activities of steam-treated and non-steam-treated nano-scale H-ZSM-5 （NHZ5） catalysts impregnated with Ag（I）, Zn（II） or P（V） have been investigated in a continuous flow fixed bed reactor. The NH3-TPD results showed that after impregnation, the Ag/NHZ5, Zn/NHZ5 and P/NHZ5 catalysts contained comparatively more strong, medium-strong and weak acid sites, respectively. Treatment with steam decreased the number of acid sites in all the catalysts, but the pore volumes in the catalysts were larger which improved carbon deposition resistance resulting in prolonged lifetimes. After 6 h of MTG reaction, the selectivity to gasoline for the steam-treated catalysts, Agrho/NHZ5, ZnH2o/NHZ5 and PH2o/NHZ5 were 70.5, 68.4 and 68.7 wt-%, respectively, whereas their respective aromatic contents in the produced gasoline were 61.9, 55.4 and 39.0 wt-%. Thus Pn2o/NHZ5 is the most promising catalyst for MTG applications which can meet the China IV gasoline standard that the amount of aromatics in gasoline should be less than 48 wt-%.
基金supported by the Major Research Plan of the National Natural Science Foundation of China(Grant No.91123022)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.10804084)
文摘Atom lithography with chromium can be utilized to fabricate a pitch standard, which is chrectly traceable to me wavelength of the laser standing waves. The result of a calibrated commercial AFM measurement demonstrates that the pitch standard is （212.8±0.1） nm with a peak-to-valley-height （PTVH） better than 20 nm. The measurement results show the high period accuracy of traceability with the standing laser wavelength （λ/2 = 212.78 nm）. The Cr nano-grating covers a 1000μm×500 μm area, with a PTVH better than 10 nm. The feature width broadening of the Cr nanostructure has been experimentally observed along the direction of the standing waves. The PTVH along the Gaussian laser direction is similar to a Gaussian distribution. Highly uniform periodic nanostructures with a big area at the millimeter scale, and the surface growth uniformity of the Cr nano-grating, show its great potential in the application of a traceable pitch standard at trans-scales.
文摘Geogas prospecting is a new method in the search for deep and/or concealed mineral deposits.The probing depth of the method comes to 300-500 m below the surface. The method, based on nuclear aualysis and accumulation sampling, has matured and become useful method of geogas prospecting, through authors' studies more than 10 years. The study of the mechanism for geogas prospecting has also been progressed. It bas been revealed that the geogas matter is in the form of nano-scale particles of the ores by the observation of scanning electron microscope (SEM). This paper summarizes the feature of the geogas anomaly, and describes its forming mechanism. A new example using geogas prospecting is given.
基金supported in part by the Institute for Guo Qiang of Tsinghua University(2019GQG1023)in part by Graduate Education and Teaching Reform Project of Tsinghua University(202007J007)+1 种基金in part by National Natural Science Foundation of China(U19B2029,62073028,61803222)in part by the Independent Research Program of Tsinghua University(2018Z05JDX002)。
文摘There are two main trends in the development of unmanned aerial vehicle(UAV)technologies:miniaturization and intellectualization,in which realizing object tracking capabilities for a nano-scale UAV is one of the most challenging problems.In this paper,we present a visual object tracking and servoing control system utilizing a tailor-made 38 g nano-scale quadrotor.A lightweight visual module is integrated to enable object tracking capabilities,and a micro positioning deck is mounted to provide accurate pose estimation.In order to be robust against object appearance variations,a novel object tracking algorithm,denoted by RMCTer,is proposed,which integrates a powerful short-term tracking module and an efficient long-term processing module.In particular,the long-term processing module can provide additional object information and modify the short-term tracking model in a timely manner.Furthermore,a positionbased visual servoing control method is proposed for the quadrotor,where an adaptive tracking controller is designed by leveraging backstepping and adaptive techniques.Stable and accurate object tracking is achieved even under disturbances.Experimental results are presented to demonstrate the high accuracy and stability of the whole tracking system.
