By using a fixed point theorem on a cone to investigate the existence of two positive periodic solutions for the following delay difference system with feedback control argument of the form {△x（n）=-b（n）x（n）＋f...By using a fixed point theorem on a cone to investigate the existence of two positive periodic solutions for the following delay difference system with feedback control argument of the form {△x（n）=-b（n）x（n）＋f（n,x（n-τ1（n））,…,x（n-τm（n））,u（n-δ（n）））,△u（n）=-η（n）u（n）＋a（n）x（n-σ（n））,n∈Z.展开更多
The present research relies on a cascade control approach through the Monte-Carlo based method in the presence of uncertainties to evaluate the performance of the real overactuated space systems.A number of potential ...The present research relies on a cascade control approach through the Monte-Carlo based method in the presence of uncertainties to evaluate the performance of the real overactuated space systems.A number of potential investigations in this area are first considered to prepare an idea with respect to state-of-the-art.The insight proposed here is organized to present attitude cascade control approach including the low thrust in connection with the high thrust to be implemented,while the aforementioned Monte-Carlo based method is carried out to guarantee the approach performance.It is noted that the investigated outcomes are efficient to handle a class of space systems presented via the center of mass and the moments of inertial.And also a number of profiles for the thrust vector and the misalignments as the disturbances all vary in its span of nominal variations.The acquired results are finally analyzed in line with some well-known benchmarks to verify the approach efficiency.The key core of finding in the research is to propose a novel 3-axis control approach to deal with all the mentioned uncertainties of space systems under control,in a synchronous manner,as long as the appropriate models in the low-high thrusts are realized.展开更多
The UPS （uninterruptible power supplies） are essential power infrastructure components of systems designed for critical application, including data centers. High availability achievement is a very important factor r...The UPS （uninterruptible power supplies） are essential power infrastructure components of systems designed for critical application, including data centers. High availability achievement is a very important factor related to UPS performance, consequently to proper critical application functionality. Generally, UPS have a limited input voltage window, referring to the nominal input voltage value. Goal of this paper is to prove larger voltage window, without affecting normal UPS operation. Larger window will result on less commutation, backup and normal mode reduction, and consequently duty time of batteries reduction, too. Thus, under these conditions, it is to be expected availability improvement. The stabilizing node model, applied at UPS＇s control part through this paper is presented. UPS＇s behavior with an implemented stabilizing node is observed at few sites. In order to analyze and conclude about UPS＇s performance under these technical conditions, simulation results are further presented.展开更多
In this article, the authors establish the local null controllability property for semilinear parabolic systems in a domain whose boundary moves in time by a single control force acting on a prescribed subdomain. The ...In this article, the authors establish the local null controllability property for semilinear parabolic systems in a domain whose boundary moves in time by a single control force acting on a prescribed subdomain. The proof is based on Kakutani＇s fixed point theorem combined with observability estimates for the associated lineaxized system.展开更多
A malaria model is formulated which includes the enhanced attractiveness of infectious humans to mosquitoes, as result of host manipulation by malaria parasite, and the human behavior, represented by insecticidetreate...A malaria model is formulated which includes the enhanced attractiveness of infectious humans to mosquitoes, as result of host manipulation by malaria parasite, and the human behavior, represented by insecticidetreated bed-nets usage. The occurrence of a backward bifurcation at R0 = 1 is shown to be possible, which implies that multiple endemic equilibria co-exist with a stable disease-free equilibrium when the basic repro- duction number is less than unity. This phenomenon is found to be caused by disease- induced human mortality. The global asymptotic stability of the endemic equilibrium for R0 〉1 is proved, by using the geometric method for global stability. Therefore, the disease becomes endemic for R0〉 1 regardless of the number of initial cases in both the human and vector populations. Finally, the impact on system dynamics of vector＇s host preferences and bed-net usage behavior is investigated.展开更多
Formation flying in the vicinity of the libration point is an important concept for space exploration and demands reliable and accurate techniques for the control of a spacecraft.On the basis of previous works,this pa...Formation flying in the vicinity of the libration point is an important concept for space exploration and demands reliable and accurate techniques for the control of a spacecraft.On the basis of previous works,this paper addresses the problem of relative orientation control of spacecraft formation flying utilizing the framework of the circular restricted three-body problem(CR3BP)with the Sun and Earth as the primary gravitational bodies.Two specific tasks are accomplished in this study.First,the tangent targeting method(TTM),an efficient two-level differential correction algorithm,is exploited to control the Chief/Deputy architecture to maintain a prespecified orientation.The time spent within the orientation error corridor between successive maneuvers is maximized while the relative separation between the vehicles is held constant at each target point.The second task is to further optimize the maneuver intervals by dropping the constraint imposed on the relative vehicle separation.Numerical investigation indicates that the number of maneuvers can be significantly reduced and the length of time between successive maneuvers can be greatly increased by utilizing the TTM.展开更多
基金Supported by the National Natural Sciences Foundation of China(10361006)Supported by the Natural Sciences Foundation of Yunnan Province(2003A0001M)Supported by the Jiangsu "Qing-lanProject" for Excellent Young Teachers in University(2006)
文摘By using a fixed point theorem on a cone to investigate the existence of two positive periodic solutions for the following delay difference system with feedback control argument of the form {△x（n）=-b（n）x（n）＋f（n,x（n-τ1（n））,…,x（n-τm（n））,u（n-δ（n）））,△u（n）=-η（n）u（n）＋a（n）x（n-σ（n））,n∈Z.
文摘The present research relies on a cascade control approach through the Monte-Carlo based method in the presence of uncertainties to evaluate the performance of the real overactuated space systems.A number of potential investigations in this area are first considered to prepare an idea with respect to state-of-the-art.The insight proposed here is organized to present attitude cascade control approach including the low thrust in connection with the high thrust to be implemented,while the aforementioned Monte-Carlo based method is carried out to guarantee the approach performance.It is noted that the investigated outcomes are efficient to handle a class of space systems presented via the center of mass and the moments of inertial.And also a number of profiles for the thrust vector and the misalignments as the disturbances all vary in its span of nominal variations.The acquired results are finally analyzed in line with some well-known benchmarks to verify the approach efficiency.The key core of finding in the research is to propose a novel 3-axis control approach to deal with all the mentioned uncertainties of space systems under control,in a synchronous manner,as long as the appropriate models in the low-high thrusts are realized.
文摘The UPS （uninterruptible power supplies） are essential power infrastructure components of systems designed for critical application, including data centers. High availability achievement is a very important factor related to UPS performance, consequently to proper critical application functionality. Generally, UPS have a limited input voltage window, referring to the nominal input voltage value. Goal of this paper is to prove larger voltage window, without affecting normal UPS operation. Larger window will result on less commutation, backup and normal mode reduction, and consequently duty time of batteries reduction, too. Thus, under these conditions, it is to be expected availability improvement. The stabilizing node model, applied at UPS＇s control part through this paper is presented. UPS＇s behavior with an implemented stabilizing node is observed at few sites. In order to analyze and conclude about UPS＇s performance under these technical conditions, simulation results are further presented.
文摘In this article, the authors establish the local null controllability property for semilinear parabolic systems in a domain whose boundary moves in time by a single control force acting on a prescribed subdomain. The proof is based on Kakutani＇s fixed point theorem combined with observability estimates for the associated lineaxized system.
文摘A malaria model is formulated which includes the enhanced attractiveness of infectious humans to mosquitoes, as result of host manipulation by malaria parasite, and the human behavior, represented by insecticidetreated bed-nets usage. The occurrence of a backward bifurcation at R0 = 1 is shown to be possible, which implies that multiple endemic equilibria co-exist with a stable disease-free equilibrium when the basic repro- duction number is less than unity. This phenomenon is found to be caused by disease- induced human mortality. The global asymptotic stability of the endemic equilibrium for R0 〉1 is proved, by using the geometric method for global stability. Therefore, the disease becomes endemic for R0〉 1 regardless of the number of initial cases in both the human and vector populations. Finally, the impact on system dynamics of vector＇s host preferences and bed-net usage behavior is investigated.
文摘Formation flying in the vicinity of the libration point is an important concept for space exploration and demands reliable and accurate techniques for the control of a spacecraft.On the basis of previous works,this paper addresses the problem of relative orientation control of spacecraft formation flying utilizing the framework of the circular restricted three-body problem(CR3BP)with the Sun and Earth as the primary gravitational bodies.Two specific tasks are accomplished in this study.First,the tangent targeting method(TTM),an efficient two-level differential correction algorithm,is exploited to control the Chief/Deputy architecture to maintain a prespecified orientation.The time spent within the orientation error corridor between successive maneuvers is maximized while the relative separation between the vehicles is held constant at each target point.The second task is to further optimize the maneuver intervals by dropping the constraint imposed on the relative vehicle separation.Numerical investigation indicates that the number of maneuvers can be significantly reduced and the length of time between successive maneuvers can be greatly increased by utilizing the TTM.
