The purpose of this study is to develop maneuvering models and systems of a simulator to improve the motion performance of autonomous underwater vehicles （AUVs） at the preliminary design stages in advance. The AUVs ...The purpose of this study is to develop maneuvering models and systems of a simulator to improve the motion performance of autonomous underwater vehicles （AUVs） at the preliminary design stages in advance. The AUVs simulation systems based on the standard submarine equations of motion in six-degree-of-freedom （6-DOF） integrated with the Euler-Rodriguez quaternion method for representing singularity-free AUV attitude and time-saving calculation, and with a nonlinear control model for maneuvering and depth control simulations, time-marching in the fourth-order Runge-Kutta scheme. For validation of the simulation codes, results of the ISiMI AUV open-loop tests including turning test and zigzag test as well as an AUV simulator on the basis of Euler-angle method were used to compare with the quaternion-based AUV simulator. The computational results from the proposed simulator agree well with those from both the ISiMI AUV experiments and the Euler-angle based simulations. Additionally, a new maneuvering procedure, namely ＂put-out＂ was implemented to test directional stability for a large-scale AUV in the proposed AUV simulator that can be considered for vehicles in space as well as in constrained planes.展开更多
The consensus problem of the distributed attitude synchronization in the spacecraft formation flying is considered.Firstly,the attitude dynamics of a rigid body spacecraft is described by modified Rodriguez parameters...The consensus problem of the distributed attitude synchronization in the spacecraft formation flying is considered.Firstly,the attitude dynamics of a rigid body spacecraft is described by modified Rodriguez parameters（MRPs）.Then global stable distributed cooperative attitude control laws are proposed for different cases.In the first case,the control law guarantees the state consensus during the attitude synchronization.In the second case,the control law ensures both the attitudes synchronizing to a desired constant attitude and the angular velocities converging at zero.In the third case,an attitude consensus control law with bounded control input is proposed.Finally,the effectiveness and validity of the control laws are demonstrated by simulations of six rigid bodies formation flying.展开更多
Soil moisture is the key link between land hydrological and ecological processes which plays an important role in the terrestrial water cycle. As extreme weather events have increased in recent years, the stochastic s...Soil moisture is the key link between land hydrological and ecological processes which plays an important role in the terrestrial water cycle. As extreme weather events have increased in recent years, the stochastic simulation of soil moisture has gradually become the focus of ecohydrology research. Based on continuous monitoring of soil moisture data from 2008 to 2011, and histor- ical precipitation data from 199l to 2011, combined with the Rodriguez-Iturbe soil moisture dynamic stochastic model, soil mois- ture dynamics and its probability density fimction in a revegetated desert area was simulated. Results show that annual soil mois- ture dynamic changes of the revegetated desert area during the growing season complied with rainfall distribution; soil moisture probability presents a single-peak distribution in the plant rhizosphere layer （0-60 cm）. The peak width in the 20 cm topsoil was wider than in other soils, and the distribution presented the strong fluctuations and multiple aggregates. The peak widths of 40 cm and 60 cm soil moisture probability distribution were small, which are in accordance with simulated results of the Rodri- guez-lturbe model. This confrms that the Rodriguez-Imrbe model has good applicability and can well simulate the statistical characteristics of soil moisture in an arid revegetated desert area.展开更多
2010-2013 The World Journal of Gastroenterology Editorial Board consists of 1352 members,representing a team of world wide experts in gastroenterology and hepatology.They are from 64 countries,including Albania(1),Arg...2010-2013 The World Journal of Gastroenterology Editorial Board consists of 1352 members,representing a team of world wide experts in gastroenterology and hepatology.They are from 64 countries,including Albania(1),Argentina(8),Australia(33)展开更多
2010-2013 The World Journal of Gastroenterology Editorial Board consists of 1352 members, representing a team of worldwide experts in gastroenterology and hepatology.
In his novel Son of Man, Augusto Roa Bastos uses images and symbols of shadows to represent the ramifications ofthe Paraguayan Dr. Jose Rodriguez de Francia＇s dictatorship. Rodriguez de Francia＇s legacy, which begin...In his novel Son of Man, Augusto Roa Bastos uses images and symbols of shadows to represent the ramifications ofthe Paraguayan Dr. Jose Rodriguez de Francia＇s dictatorship. Rodriguez de Francia＇s legacy, which begins duringthe postcolonial years and extends well into the 20th century, resonates in the novel in soeio-political structures andcharacters＇ ideologies and behaviors. It allows for plantation owners to enslave workers and their families; itconfines and oppresses people through unfounded legends and myths; and among other things, it creates a falseidea of purpose and patriotism in the Chaco War （1932-1935）, which in the end lets down the soldiers. Tocounteract these deleterious social conditions, Roa Bastos creates surreal characters, such as a fantastic helper whoaids plantation workers to escape dehumanizing situations. Roa Bastos also narrates how the people in Itapr, asmall town, make an idol of a Christ statue carved by one of their own. However, when the two Goiburfl brothersreplace the statue by crucifying their sister＇s rapist, the people＇s myth is destroyed. Likewise, Roa Bastos availshimself of Christian and Catholic concepts and symbols to transpose them into a humanistic ideology so as toconvey hope to his people through a new perspective. In this way, a new Annunciation takes place when the son ofa raped woman is born. In the end, Roa Bastos lets the course of these warped transpositions take their logicaldenouement： In the absence of a purpose beyond an earthly existence, death becomes the narrator＇s option.展开更多
文摘The purpose of this study is to develop maneuvering models and systems of a simulator to improve the motion performance of autonomous underwater vehicles （AUVs） at the preliminary design stages in advance. The AUVs simulation systems based on the standard submarine equations of motion in six-degree-of-freedom （6-DOF） integrated with the Euler-Rodriguez quaternion method for representing singularity-free AUV attitude and time-saving calculation, and with a nonlinear control model for maneuvering and depth control simulations, time-marching in the fourth-order Runge-Kutta scheme. For validation of the simulation codes, results of the ISiMI AUV open-loop tests including turning test and zigzag test as well as an AUV simulator on the basis of Euler-angle method were used to compare with the quaternion-based AUV simulator. The computational results from the proposed simulator agree well with those from both the ISiMI AUV experiments and the Euler-angle based simulations. Additionally, a new maneuvering procedure, namely ＂put-out＂ was implemented to test directional stability for a large-scale AUV in the proposed AUV simulator that can be considered for vehicles in space as well as in constrained planes.
基金supported by the National Science Foundation of China (6097406260972119)the Chinese Ministry of Science and Intergovernmental Cooperation Project(2009DFA12870)
文摘The consensus problem of the distributed attitude synchronization in the spacecraft formation flying is considered.Firstly,the attitude dynamics of a rigid body spacecraft is described by modified Rodriguez parameters（MRPs）.Then global stable distributed cooperative attitude control laws are proposed for different cases.In the first case,the control law guarantees the state consensus during the attitude synchronization.In the second case,the control law ensures both the attitudes synchronizing to a desired constant attitude and the angular velocities converging at zero.In the third case,an attitude consensus control law with bounded control input is proposed.Finally,the effectiveness and validity of the control laws are demonstrated by simulations of six rigid bodies formation flying.
基金supported by the Key Orientation Project of Chinese Academy of Sciences(KZCX2-EW-301-3)Talented Young Scientist Fund of the Cold and Arid Regions Environmental and Engineering Research Institute,CAS(51Y251971)National Natural Scientific Foundation of China(41101054,41201084)
文摘Soil moisture is the key link between land hydrological and ecological processes which plays an important role in the terrestrial water cycle. As extreme weather events have increased in recent years, the stochastic simulation of soil moisture has gradually become the focus of ecohydrology research. Based on continuous monitoring of soil moisture data from 2008 to 2011, and histor- ical precipitation data from 199l to 2011, combined with the Rodriguez-Iturbe soil moisture dynamic stochastic model, soil mois- ture dynamics and its probability density fimction in a revegetated desert area was simulated. Results show that annual soil mois- ture dynamic changes of the revegetated desert area during the growing season complied with rainfall distribution; soil moisture probability presents a single-peak distribution in the plant rhizosphere layer （0-60 cm）. The peak width in the 20 cm topsoil was wider than in other soils, and the distribution presented the strong fluctuations and multiple aggregates. The peak widths of 40 cm and 60 cm soil moisture probability distribution were small, which are in accordance with simulated results of the Rodri- guez-lturbe model. This confrms that the Rodriguez-Imrbe model has good applicability and can well simulate the statistical characteristics of soil moisture in an arid revegetated desert area.
文摘2010-2013 The World Journal of Gastroenterology Editorial Board consists of 1352 members,representing a team of world wide experts in gastroenterology and hepatology.They are from 64 countries,including Albania(1),Argentina(8),Australia(33)
文摘2010-2013 The World Journal of Gastroenterology Editorial Board consists of 1352 members, representing a team of worldwide experts in gastroenterology and hepatology.
文摘In his novel Son of Man, Augusto Roa Bastos uses images and symbols of shadows to represent the ramifications ofthe Paraguayan Dr. Jose Rodriguez de Francia＇s dictatorship. Rodriguez de Francia＇s legacy, which begins duringthe postcolonial years and extends well into the 20th century, resonates in the novel in soeio-political structures andcharacters＇ ideologies and behaviors. It allows for plantation owners to enslave workers and their families; itconfines and oppresses people through unfounded legends and myths; and among other things, it creates a falseidea of purpose and patriotism in the Chaco War （1932-1935）, which in the end lets down the soldiers. Tocounteract these deleterious social conditions, Roa Bastos creates surreal characters, such as a fantastic helper whoaids plantation workers to escape dehumanizing situations. Roa Bastos also narrates how the people in Itapr, asmall town, make an idol of a Christ statue carved by one of their own. However, when the two Goiburfl brothersreplace the statue by crucifying their sister＇s rapist, the people＇s myth is destroyed. Likewise, Roa Bastos availshimself of Christian and Catholic concepts and symbols to transpose them into a humanistic ideology so as toconvey hope to his people through a new perspective. In this way, a new Annunciation takes place when the son ofa raped woman is born. In the end, Roa Bastos lets the course of these warped transpositions take their logicaldenouement： In the absence of a purpose beyond an earthly existence, death becomes the narrator＇s option.
