Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principl...Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principle. A feedback control strategy of the momentum wheel is ap- plied for the attitude maneuver. The residual nutation of the spacecraft in maneuver process changes with some chosen parameters, such as steady state time, locations of the liq- uid container and the appendage, and appendage parame- ters. The results indicate that locations in the second and fourth quadrants of the body-fixed coordinate system and the second quadrant of the wall of the main body are better choices for.placing the liquid containers and the appendage than other locations if they can be placed randomly. Higher density and thicker cross section are better for lowering the residual nutation if they can be changed. Light appendage can be modeled as a rigid body, which results in a larger residual nutation than a flexible model though. The resid- ual nutation decreases with increasing absolute value of the initial sloshing angular height.展开更多
Klippel-Trénaunay syndrome (KTS)is arare angio-osteo-hypertrophic syndrome characterized by vascular malformations,soft tissue and/or bone hypertrophy, and varicose veins.For the purpose of describing the imaging...Klippel-Trénaunay syndrome (KTS)is arare angio-osteo-hypertrophic syndrome characterized by vascular malformations,soft tissue and/or bone hypertrophy, and varicose veins.For the purpose of describing the imaging findings and elucidating the role of medical imaging in the diagnosis and assessment of patient with KTS,we have reviewed the imaging data of 14 KTS patients.The imaging features on different imaging modalities were analyzed.Unilateral lower limb involvement was evident in 71% of cases (n=10)and bilateral but asymmetric lower limb involvement in the remaining 29% of cases (n=4).The most commonly depicted imaging features were varicosities in 93% (n=13),muscle hypertrophy in 79%(n=11)and venous anomalies in 64%(n=9).Other less common imaging findings included lymphedema in 29%(n=4),arterial malformations 29%(n=4),soft tissue hemangiomas 21%(n=3),pelvic and thigh phleboliths 21%(n=3), venous aneurysrns 21%(n=3),bone abnormalities 14%(n=2)and lymphadenopathy 14%(n=2).A severe unilateral lower limb deformity resulting in contractures and muscle atrophy of the whole limb was depicted in 1 case.The pathognomonic marginal vein of Servelle was identified in 2 cases.AV shunt was highly suspected in 4 cases and was confirmed by DSA in 1 case,making Klippel-Trénaunay-Weber syndrome a more apt diagnosis.Associated ipsilateral duplicated renal artery:was found in 1 case.We have concluded that medical imaging is the cornerstone in the.diagnosis and assessment of severity and complications,follow-up and differentiation of KTS from other similar conditions.Different imaging modalities play complementary roles in the evaluation of KTS patients.展开更多
This paper is mainly concerned with the coupling dynamic analysis of a complex spacecraft consisting of one main rigid platform, multiple liquid-filled cylindrical tanks, and a number of flexible appendages. Firstly, ...This paper is mainly concerned with the coupling dynamic analysis of a complex spacecraft consisting of one main rigid platform, multiple liquid-filled cylindrical tanks, and a number of flexible appendages. Firstly, the carrier potential function equations of liquid in the tanks are deduced according to the wall boundary conditions. Through employ- ing the Fourier-Bessel series expansion method, the dynamic boundaries conditions on a curved free-surface under a low-gravity environment are transformed to general simple differential equations and the rigid-liquid coupled sloshing dynamic state equations of liquid in tanks are obtained. The state vectors of rigid-liquid coupled equations are composed with the modal coordinates of the relative potential func- tion and the modal coordinates of wave height. Based on the B ernoulli-Euler beam theory and the D＇Alembert＇s prin- ciple, the rigid-flexible coupled dynamic state equations of flexible appendages are directly derived, and the coordi- nate transform matrixes of maneuvering flexible appendages are precisely computed as time-varying. Then, the cou- pling dynamics state equations of the overall system of the spacecraft are modularly built by means of the Lagrange＇s equations in terms of quasi-coordinates. Lastly, the cou-piing dynamic performances of a typical complex spacecraft are studied. The availability and reliability of the presented method are also confirmed.展开更多
This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Ber...This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Bernoulli beams, and the sloshing liquid is modeled as in two modes multi-spring-mass models; the governing equations of this coupled system are developed by using Hamilton＇s prin- ciple. Numerical results show that the spacecraft attitude responses consist of a quasi-static displacement and superim- posed vibration. Then, we design an adaptive sliding mode and use the Lyapunov approach control law to control the attitude disturbance and suppress the thermal jitter and liq- uid sloshing for the fuel filled flexible spacecraft subject to the thermal payload. Numerical results are presented to verify the efficiency of the hybrid control methods. The results show that the adaptive sliding mode method might be effective to handle the steady-state errors and the Lyapunov control algo- rithm would suppress the residual vibration.展开更多
The Internet based cyber-physical world has profoundly changed the information environment for the development of artificial intelligence(AI), bringing a new wave of AI research and promoting it into the new era of AI...The Internet based cyber-physical world has profoundly changed the information environment for the development of artificial intelligence(AI), bringing a new wave of AI research and promoting it into the new era of AI 2.0. As one of the most prominent characteristics of research in AI 2.0 era, crowd intelligence has attracted much attention from both industry and research communities. Specifically, crowd intelligence provides a novel problem-solving paradigm through gathering the intelligence of crowds to address challenges. In particular, due to the rapid development of the sharing economy, crowd intelligence not only becomes a new approach to solving scientific challenges, but has also been integrated into all kinds of application scenarios in daily life, e.g., online-tooffline(O2O) application, real-time traffic monitoring, and logistics management. In this paper, we survey existing studies of crowd intelligence. First, we describe the concept of crowd intelligence, and explain its relationship to the existing related concepts, e.g., crowdsourcing and human computation. Then, we introduce four categories of representative crowd intelligence platforms. We summarize three core research problems and the state-of-the-art techniques of crowd intelligence. Finally, we discuss promising future research directions of crowd intelligence.展开更多
A series of hydroxide conductive polymers QTBMs carrying dense aromatic side-chain quaternary ammonium groups has been synthesized by using a new monomer of 3,3＇-di（3＂,5＂-dimethylphenyl）-4,4＇-difluorodiphenyl su...A series of hydroxide conductive polymers QTBMs carrying dense aromatic side-chain quaternary ammonium groups has been synthesized by using a new monomer of 3,3＇-di（3＂,5＂-dimethylphenyl）-4,4＇-difluorodiphenyl sulfone and other commercial monomers via polycondensation reaction, and subsequent bromination, quaternization and alkalization. The chemical structures of the ionomers were confirmed by 1H- and 13C-NMR spectroscopy. Water uptake, swelling ratio, hydroxide conductivity, the number of bonded water per ammonium group （A）, volumetric ion exchange capacity （IECvwet）, mechanical and thermal properties, and chemical stability were systematically evaluated for the series of QTBMs membranes. QTBMs showed IECs ranging from 1.02 meq·g-1 to 2.11 meq·g-1; in particular, QTBM-60 membrane with the highest IEC （2.11 meq·g-1） had very high hydroxide ion conductivity of 131.9 mS·cm-1 at 80 ℃, which was attributed to the well assembled nano-channels with distinct phase separation evidenced by small-angle X-ray scattering （SAXS）. It was found that the hydrated QTBMs membranes were mechanically stable with moderate water uptakes and swelling ratios, high chemical stability under the harsh alkaline conditions. This work provides a facile way to prepare anion exchange membranes （AEMs） with high performances for the application in alkaline fuel cells.展开更多
Recently, crowdsourcing platforms have attracted a number of citizens to perform a variety of locationspecific tasks. However, most existing approaches consider the arrangement of a set of tasks for a set of crowd wor...Recently, crowdsourcing platforms have attracted a number of citizens to perform a variety of locationspecific tasks. However, most existing approaches consider the arrangement of a set of tasks for a set of crowd workers, while few consider crowd workers arriving in a dynamic manner. Therefore, how to arrange suitable location-specific tasks to a set of crowd workers such that the crowd workers obtain maximum satisfaction when arriving sequentially represents a challenge. To address the limitation of existing approaches, we first identify a more general and useful model that considers not only the arrangement of a set of tasks to a set of crowd workers, but also all the dynamic arrivals of all crowd workers. Then, we present an effective crowd-task model which is applied to offline and online settings, respectively. To solve the problem in an offline setting, we first observe the characteristics of task planning(CTP) and devise a CTP algorithm to solve the problem. We also propose an effective greedy method and integrated simulated annealing(ISA) techniques to improve the algorithm performance. To solve the problem in an online setting, we develop a greedy algorithm for task planning. Finally, we verify the effectiveness and efficiency of the proposed solutions through extensive experiments using real and synthetic datasets.展开更多
基金supported by the National Natural Science Foundation of China (11072030)
文摘Attitude maneuver of liquid-filled spacecraft with an appendage as a cantilever beam by momentum wheel is studied. The dynamic equations are derived by conserva- tion of angular momentum and force equilibrium principle. A feedback control strategy of the momentum wheel is ap- plied for the attitude maneuver. The residual nutation of the spacecraft in maneuver process changes with some chosen parameters, such as steady state time, locations of the liq- uid container and the appendage, and appendage parame- ters. The results indicate that locations in the second and fourth quadrants of the body-fixed coordinate system and the second quadrant of the wall of the main body are better choices for.placing the liquid containers and the appendage than other locations if they can be placed randomly. Higher density and thicker cross section are better for lowering the residual nutation if they can be changed. Light appendage can be modeled as a rigid body, which results in a larger residual nutation than a flexible model though. The resid- ual nutation decreases with increasing absolute value of the initial sloshing angular height.
文摘Klippel-Trénaunay syndrome (KTS)is arare angio-osteo-hypertrophic syndrome characterized by vascular malformations,soft tissue and/or bone hypertrophy, and varicose veins.For the purpose of describing the imaging findings and elucidating the role of medical imaging in the diagnosis and assessment of patient with KTS,we have reviewed the imaging data of 14 KTS patients.The imaging features on different imaging modalities were analyzed.Unilateral lower limb involvement was evident in 71% of cases (n=10)and bilateral but asymmetric lower limb involvement in the remaining 29% of cases (n=4).The most commonly depicted imaging features were varicosities in 93% (n=13),muscle hypertrophy in 79%(n=11)and venous anomalies in 64%(n=9).Other less common imaging findings included lymphedema in 29%(n=4),arterial malformations 29%(n=4),soft tissue hemangiomas 21%(n=3),pelvic and thigh phleboliths 21%(n=3), venous aneurysrns 21%(n=3),bone abnormalities 14%(n=2)and lymphadenopathy 14%(n=2).A severe unilateral lower limb deformity resulting in contractures and muscle atrophy of the whole limb was depicted in 1 case.The pathognomonic marginal vein of Servelle was identified in 2 cases.AV shunt was highly suspected in 4 cases and was confirmed by DSA in 1 case,making Klippel-Trénaunay-Weber syndrome a more apt diagnosis.Associated ipsilateral duplicated renal artery:was found in 1 case.We have concluded that medical imaging is the cornerstone in the.diagnosis and assessment of severity and complications,follow-up and differentiation of KTS from other similar conditions.Different imaging modalities play complementary roles in the evaluation of KTS patients.
基金project was supported by the National Natural Science Foundation of China (Grants 11472041, 11302244, 11532002)Guangxi Natural Science Foundation (2015GXNSFBA 139013)
文摘This paper is mainly concerned with the coupling dynamic analysis of a complex spacecraft consisting of one main rigid platform, multiple liquid-filled cylindrical tanks, and a number of flexible appendages. Firstly, the carrier potential function equations of liquid in the tanks are deduced according to the wall boundary conditions. Through employ- ing the Fourier-Bessel series expansion method, the dynamic boundaries conditions on a curved free-surface under a low-gravity environment are transformed to general simple differential equations and the rigid-liquid coupled sloshing dynamic state equations of liquid in tanks are obtained. The state vectors of rigid-liquid coupled equations are composed with the modal coordinates of the relative potential func- tion and the modal coordinates of wave height. Based on the B ernoulli-Euler beam theory and the D＇Alembert＇s prin- ciple, the rigid-flexible coupled dynamic state equations of flexible appendages are directly derived, and the coordi- nate transform matrixes of maneuvering flexible appendages are precisely computed as time-varying. Then, the cou- pling dynamics state equations of the overall system of the spacecraft are modularly built by means of the Lagrange＇s equations in terms of quasi-coordinates. Lastly, the cou-piing dynamic performances of a typical complex spacecraft are studied. The availability and reliability of the presented method are also confirmed.
基金supported by the National Natural Science Foundation of China(NNSFC)(Grant 11472041)the Research Fund for the Doctoral Program of Higher Education of China(Grant 20131101110002)
文摘This paper is mainly focused on the attitude dynamics and control of a fuel-filled flexible spacecraft sub- jected to the thermal payload during eclipse transitions. The flexible appendages are considered as Euler-Bernoulli beams, and the sloshing liquid is modeled as in two modes multi-spring-mass models; the governing equations of this coupled system are developed by using Hamilton＇s prin- ciple. Numerical results show that the spacecraft attitude responses consist of a quasi-static displacement and superim- posed vibration. Then, we design an adaptive sliding mode and use the Lyapunov approach control law to control the attitude disturbance and suppress the thermal jitter and liq- uid sloshing for the fuel filled flexible spacecraft subject to the thermal payload. Numerical results are presented to verify the efficiency of the hybrid control methods. The results show that the adaptive sliding mode method might be effective to handle the steady-state errors and the Lyapunov control algo- rithm would suppress the residual vibration.
基金supported by the National Natural Science Foundation of China(No.61532004)
文摘The Internet based cyber-physical world has profoundly changed the information environment for the development of artificial intelligence(AI), bringing a new wave of AI research and promoting it into the new era of AI 2.0. As one of the most prominent characteristics of research in AI 2.0 era, crowd intelligence has attracted much attention from both industry and research communities. Specifically, crowd intelligence provides a novel problem-solving paradigm through gathering the intelligence of crowds to address challenges. In particular, due to the rapid development of the sharing economy, crowd intelligence not only becomes a new approach to solving scientific challenges, but has also been integrated into all kinds of application scenarios in daily life, e.g., online-tooffline(O2O) application, real-time traffic monitoring, and logistics management. In this paper, we survey existing studies of crowd intelligence. First, we describe the concept of crowd intelligence, and explain its relationship to the existing related concepts, e.g., crowdsourcing and human computation. Then, we introduce four categories of representative crowd intelligence platforms. We summarize three core research problems and the state-of-the-art techniques of crowd intelligence. Finally, we discuss promising future research directions of crowd intelligence.
基金supported by the National Natural Science Foundation of China(No.51173045)Student Research Program(SRP) Funds of South China University of Technology(Nos.105612015S165 and 105612016S198)
文摘A series of hydroxide conductive polymers QTBMs carrying dense aromatic side-chain quaternary ammonium groups has been synthesized by using a new monomer of 3,3＇-di（3＂,5＂-dimethylphenyl）-4,4＇-difluorodiphenyl sulfone and other commercial monomers via polycondensation reaction, and subsequent bromination, quaternization and alkalization. The chemical structures of the ionomers were confirmed by 1H- and 13C-NMR spectroscopy. Water uptake, swelling ratio, hydroxide conductivity, the number of bonded water per ammonium group （A）, volumetric ion exchange capacity （IECvwet）, mechanical and thermal properties, and chemical stability were systematically evaluated for the series of QTBMs membranes. QTBMs showed IECs ranging from 1.02 meq·g-1 to 2.11 meq·g-1; in particular, QTBM-60 membrane with the highest IEC （2.11 meq·g-1） had very high hydroxide ion conductivity of 131.9 mS·cm-1 at 80 ℃, which was attributed to the well assembled nano-channels with distinct phase separation evidenced by small-angle X-ray scattering （SAXS）. It was found that the hydrated QTBMs membranes were mechanically stable with moderate water uptakes and swelling ratios, high chemical stability under the harsh alkaline conditions. This work provides a facile way to prepare anion exchange membranes （AEMs） with high performances for the application in alkaline fuel cells.
基金supported by the National High-Tech R&D Program(863) of China(No.2014AA015203)
文摘Recently, crowdsourcing platforms have attracted a number of citizens to perform a variety of locationspecific tasks. However, most existing approaches consider the arrangement of a set of tasks for a set of crowd workers, while few consider crowd workers arriving in a dynamic manner. Therefore, how to arrange suitable location-specific tasks to a set of crowd workers such that the crowd workers obtain maximum satisfaction when arriving sequentially represents a challenge. To address the limitation of existing approaches, we first identify a more general and useful model that considers not only the arrangement of a set of tasks to a set of crowd workers, but also all the dynamic arrivals of all crowd workers. Then, we present an effective crowd-task model which is applied to offline and online settings, respectively. To solve the problem in an offline setting, we first observe the characteristics of task planning(CTP) and devise a CTP algorithm to solve the problem. We also propose an effective greedy method and integrated simulated annealing(ISA) techniques to improve the algorithm performance. To solve the problem in an online setting, we develop a greedy algorithm for task planning. Finally, we verify the effectiveness and efficiency of the proposed solutions through extensive experiments using real and synthetic datasets.
