In the passive turning state,the helicopter turns through the tail rotor force and the friction of the ground to the tire.In practice,it is found that the helicopter will turn difficultly under low aircraft ground spe...In the passive turning state,the helicopter turns through the tail rotor force and the friction of the ground to the tire.In practice,it is found that the helicopter will turn difficultly under low aircraft ground speed or static state.This paper takes a certain type of helicopter as the research object,and establishes the dynamic model of helicopter ground turning motion based on the basic theory of dynamics.This model takes into account the six-degree-of-freedom motion model of the helicopter body,the motion model of the landing gear buffer,the tire mechanics model and the friction characteristics of the strut friction disc.The dynamic simulation of the helicopter right angle turn and static turn is carried out,and the influence of parameters such as tail rotor pull,taxi speed,tail wheel stability distance on the dynamic response of the turn is studied.The results show that under the same ground taxing speed,the tail wheel angle increases with the increase of tail rotor force.When the tail rotor force is the same,the tail wheel angle increases with the increase of ground taxing speed.When the helicopter is completely static,it is the most difficult to turn,which requires much bigger force of the tail rotor to turn.In addition,the change of the stability distance of the tail wheel has an obvious influence on the turning.When the stability distance is doubled,the tail rotor force will be reduced by 30%to the same angle of the tail wheel.展开更多
One of the central challenges of sustainable transition is the changing of the buildings. This involves social, cultural,political, and regulatory dynamics. Critically using transition theory conceptualization of a wo...One of the central challenges of sustainable transition is the changing of the buildings. This involves social, cultural,political, and regulatory dynamics. Critically using transition theory conceptualization of a world of dynamics, the paper reviews institutional theory and actor network approaches in an attempt to better account for contemporary developments in Europe, encompassing EU reforms as well as multiple competing concepts. The emergence of ＂passive houses＂ in Denmark is used as a case of transition dynamics. The concept was developed in Germany and imported into Denmark. It is a technological niche, encompassing technologies, players, improvisation, and early customers. Passive houses have entered into fierce competition with other future institutions such as LEED （Leadership in Energy and Environmental Design）, DGNB （German Sustainable Building Council）/green building council, and active houses. Passive houses were at the outset a well-developed upcoming institution with design principles, software, certification and numerous reference buildings, strong enough to be a challenger institution. They are promoted by a characteristic alliance of architects, consulting engineers, a few clients, and an architect school, whereas the other concepts exhibit their specific actor alliances. Yet passive houses experience barriers such as the reputation of being expensive and non-user friendly, and are currently surpassed by the other concepts.展开更多
Liposomes are used as carriers for targeted drug delivery by the intravenous route. The aim of our study was to prepare lomustine loaded liposomes （CCNU-Lips） and evaluate its physicochemical properties and the tiss...Liposomes are used as carriers for targeted drug delivery by the intravenous route. The aim of our study was to prepare lomustine loaded liposomes （CCNU-Lips） and evaluate its physicochemical properties and the tissue targeting after intravenous （i.v.） injection. CCNU-Lips were prepared by film dispersion method. In vitro drug release was investigated in phosphate-buffered saline （pH 6.8） at 37℃. The concentrations of CCNU in selected organs were determined using reversed-phase high-performance liquid chromatography （HPLC） following i.v. administration of CCNU-Lips and inclusion complex solution of CCNU with hydroxypropyl-β-cyclodextrin （CCNU-Sol）. CCNU-Lips had an average diameter of （189.8±28.5） nm with a zeta potential of （-19.13±0.12） mV and the in vitro drug release was monitored for up to 3 d, and the release behavior was in accordance with Weibull-equation. The CCNU-Lips exhibited a longer elimination half life （t1/2β） in vivo compared with CCNU-Sol after i.v. injection to New Zealand rabbits. The encapsulation of lomustine in liposomes also changed its biodistribution in mice. CCNU-Lips showed significant brain targeting with AUC, Te and Re of the brain all showing obvious elevation. These results indicated that CCNU-Lips were promising passive targeting formulation to the brain.展开更多
Using the fuzzy rule-based classification method, normalized difference vegetation index (NDVI) images acquired from 1982 to 1998 were classified into seventeen phases. Based on these classification images, a probabil...Using the fuzzy rule-based classification method, normalized difference vegetation index (NDVI) images acquired from 1982 to 1998 were classified into seventeen phases. Based on these classification images, a probabilistic cellular automata-Markov Chain model was developed and used to simulate a land cover scenario of China for the year 2014. Spatiotemporal dynamics of land use/cover in China from 1982 to 2014 were then analyzed and evaluated. The results showed that the change trends of land cover type from 1998 to 2014 would be contrary to those from 1982 to 1998. In particular, forestland and grassland areas decreased by 1.56% and 1.46%, respectively, from 1982 to 1998, and should increase by 1.5% and 2.3% from 1998 to 2014, respectively.展开更多
基金supported in part by the Fundamental Research Funds for the Central Universi-ties(No.NP2022416)the Aeronautical Science Founda⁃tion of China(No.20180627210315).
文摘In the passive turning state,the helicopter turns through the tail rotor force and the friction of the ground to the tire.In practice,it is found that the helicopter will turn difficultly under low aircraft ground speed or static state.This paper takes a certain type of helicopter as the research object,and establishes the dynamic model of helicopter ground turning motion based on the basic theory of dynamics.This model takes into account the six-degree-of-freedom motion model of the helicopter body,the motion model of the landing gear buffer,the tire mechanics model and the friction characteristics of the strut friction disc.The dynamic simulation of the helicopter right angle turn and static turn is carried out,and the influence of parameters such as tail rotor pull,taxi speed,tail wheel stability distance on the dynamic response of the turn is studied.The results show that under the same ground taxing speed,the tail wheel angle increases with the increase of tail rotor force.When the tail rotor force is the same,the tail wheel angle increases with the increase of ground taxing speed.When the helicopter is completely static,it is the most difficult to turn,which requires much bigger force of the tail rotor to turn.In addition,the change of the stability distance of the tail wheel has an obvious influence on the turning.When the stability distance is doubled,the tail rotor force will be reduced by 30%to the same angle of the tail wheel.
文摘One of the central challenges of sustainable transition is the changing of the buildings. This involves social, cultural,political, and regulatory dynamics. Critically using transition theory conceptualization of a world of dynamics, the paper reviews institutional theory and actor network approaches in an attempt to better account for contemporary developments in Europe, encompassing EU reforms as well as multiple competing concepts. The emergence of ＂passive houses＂ in Denmark is used as a case of transition dynamics. The concept was developed in Germany and imported into Denmark. It is a technological niche, encompassing technologies, players, improvisation, and early customers. Passive houses have entered into fierce competition with other future institutions such as LEED （Leadership in Energy and Environmental Design）, DGNB （German Sustainable Building Council）/green building council, and active houses. Passive houses were at the outset a well-developed upcoming institution with design principles, software, certification and numerous reference buildings, strong enough to be a challenger institution. They are promoted by a characteristic alliance of architects, consulting engineers, a few clients, and an architect school, whereas the other concepts exhibit their specific actor alliances. Yet passive houses experience barriers such as the reputation of being expensive and non-user friendly, and are currently surpassed by the other concepts.
文摘Liposomes are used as carriers for targeted drug delivery by the intravenous route. The aim of our study was to prepare lomustine loaded liposomes （CCNU-Lips） and evaluate its physicochemical properties and the tissue targeting after intravenous （i.v.） injection. CCNU-Lips were prepared by film dispersion method. In vitro drug release was investigated in phosphate-buffered saline （pH 6.8） at 37℃. The concentrations of CCNU in selected organs were determined using reversed-phase high-performance liquid chromatography （HPLC） following i.v. administration of CCNU-Lips and inclusion complex solution of CCNU with hydroxypropyl-β-cyclodextrin （CCNU-Sol）. CCNU-Lips had an average diameter of （189.8±28.5） nm with a zeta potential of （-19.13±0.12） mV and the in vitro drug release was monitored for up to 3 d, and the release behavior was in accordance with Weibull-equation. The CCNU-Lips exhibited a longer elimination half life （t1/2β） in vivo compared with CCNU-Sol after i.v. injection to New Zealand rabbits. The encapsulation of lomustine in liposomes also changed its biodistribution in mice. CCNU-Lips showed significant brain targeting with AUC, Te and Re of the brain all showing obvious elevation. These results indicated that CCNU-Lips were promising passive targeting formulation to the brain.
基金Supported by the National Natural Science Foundation of China(No.30730021)the Applied Basic Research Programs of Yunnan Province,China(Nos.2011FZ140 and 2010CD047)
文摘Using the fuzzy rule-based classification method, normalized difference vegetation index (NDVI) images acquired from 1982 to 1998 were classified into seventeen phases. Based on these classification images, a probabilistic cellular automata-Markov Chain model was developed and used to simulate a land cover scenario of China for the year 2014. Spatiotemporal dynamics of land use/cover in China from 1982 to 2014 were then analyzed and evaluated. The results showed that the change trends of land cover type from 1998 to 2014 would be contrary to those from 1982 to 1998. In particular, forestland and grassland areas decreased by 1.56% and 1.46%, respectively, from 1982 to 1998, and should increase by 1.5% and 2.3% from 1998 to 2014, respectively.
