Access to potable water is a serious problem that plagues most communities in 3rd World countries. Governments to this effect have developed texts governing the water sector that often encourage local participation. T...Access to potable water is a serious problem that plagues most communities in 3rd World countries. Governments to this effect have developed texts governing the water sector that often encourage local participation. Thus, in pursuance of the Sustainable Development Goals (SDGs) set up after 2015 following the failure to achieve the MDGs by the UN, many countries still do not attain the set objectives today. GICABAF (A Common Initiative Group) in 2012 financed the installation of pipe-borne water network in Sa’ah Batsengl’a locality in Nkong Zem Council of West Cameroon. But the problem observed in its management is that no database was put in place to ease its management which cannot guarantee sustainability. This study proposes a computerised database to manage the water network. To conduct this study, a six months internship was carried out with GICAPBAF where GPS was used to track all the pipes and locate other phenomena. Then a set questionnaire was administered to subscribers and managers in order to understand the functioning of the network so as to propose the GIS-AWS. These data collected were then treated and analysed in a GIS software (MapInfo). The generated database was then coupled to a flow simulation model in a distribution network (Epanet) which gave rise to GIS-Epanet. This was realised through the use of plugin GHydraulics of QGis and the MapBasic language of MapInfo. This will enable present and future managers of the project to master the network thereby facilitating the detection of any malfunctioning for prompt reaction. This simply summarises the putting in place of GIS Applied to Water Supply (GIS-AWS).展开更多
In this paper,the performance of two distinct classes of feedback guidance algorithms is evaluated for a spacecraft rendezvous problem utilizing a continuous low-thrust propulsion system.They are the DG(Differential G...In this paper,the performance of two distinct classes of feedback guidance algorithms is evaluated for a spacecraft rendezvous problem utilizing a continuous low-thrust propulsion system.They are the DG(Differential Geometric)and ZEM/ZEV(Zero-Effort-Miss/Zero-Effort-Velocity)feedback guidance algorithms.Even though these two guidance algorithms do not attempt to minimize the onboard fuel consumption orΔV directly,theΔV requirement is used as a measure of their orbital rendezvous performance for various initial conditions and a wide range of the rendezvous time(within less than one orbital period of the target vehicle).For the DG guidance,the effects of its guidance parameter and terminal time on the closed-loop performance are evaluated by numerical simulations.For the ZEM/ZEV guidance,its nearfuel-optimality is further demonstrated for a rapid,short-range orbital rendezvous,in comparison with the corresponding open-loop optimal solutions.Furthermore,the poorΔV performance of the ZEM/ZEV guidance for a slow,long-range orbital rendezvous is remedied by simply adding an initial drift phase.The ZEM/ZEV feedback guidance algorithm and its appropriate variants are then shown to be a simple practical solution to a non-impulsive rendezvous problem,in comparison with the DG guidance as well as the open-loop optimal guidance.展开更多
This paper investigates a problem of determining the optimal terminal-time or time-to-go of the ZEM/ZEV(Zero-E ort-Miss/Zero-E ort-Velocity)feedback guidance law for a variety of orbital intercept or rendezvous maneuv...This paper investigates a problem of determining the optimal terminal-time or time-to-go of the ZEM/ZEV(Zero-E ort-Miss/Zero-E ort-Velocity)feedback guidance law for a variety of orbital intercept or rendezvous maneuvers.A generalized ZEM/ZEV guidance problem,whose objective is to minimize a combination of the control energy and terminal time,is examined.Algebraic equations whose solution provides the optimal terminal-time of the orbital intercept/rendezvous problems are derived based on the optimal control theory.The e ectiveness of the proposed approach is demonstrated for various orbital maneuver problems.展开更多
A conflict of three players, including an attacker, a defender, and a target with bounded control is discussed based on the differential game theories in which the target and the defender use an optimal pursuit strate...A conflict of three players, including an attacker, a defender, and a target with bounded control is discussed based on the differential game theories in which the target and the defender use an optimal pursuit strategy. The current approach chooses the miss distance as the outcome of the conflict. Different optimal guidance laws are investigated, and feasible conditions are analyzed for the attacker to accomplish an attacking task. For some given conditions, the attacker cannot intercept the target by only using a one-to-one optimal pursuit guidance law; thus, a guidance law for the attacker to reach a critical safe value is investigated.Specifically, the guidance law is divided into two parts. Before the engagement time between the defender and the attacker, the attacker uses this derived guidance law to guarantee that the evasion distance from the defender is safe, and that the zero-effort-miss(ZEM) distance between the attacker and the target is the smallest.After that engagement time, the attacker uses the optimal one-toone guidance law to accomplish the pursuit task. The advantages and limited conditions of these derived guidance laws are also investigated by using nonlinear simulations.展开更多
文摘Access to potable water is a serious problem that plagues most communities in 3rd World countries. Governments to this effect have developed texts governing the water sector that often encourage local participation. Thus, in pursuance of the Sustainable Development Goals (SDGs) set up after 2015 following the failure to achieve the MDGs by the UN, many countries still do not attain the set objectives today. GICABAF (A Common Initiative Group) in 2012 financed the installation of pipe-borne water network in Sa’ah Batsengl’a locality in Nkong Zem Council of West Cameroon. But the problem observed in its management is that no database was put in place to ease its management which cannot guarantee sustainability. This study proposes a computerised database to manage the water network. To conduct this study, a six months internship was carried out with GICAPBAF where GPS was used to track all the pipes and locate other phenomena. Then a set questionnaire was administered to subscribers and managers in order to understand the functioning of the network so as to propose the GIS-AWS. These data collected were then treated and analysed in a GIS software (MapInfo). The generated database was then coupled to a flow simulation model in a distribution network (Epanet) which gave rise to GIS-Epanet. This was realised through the use of plugin GHydraulics of QGis and the MapBasic language of MapInfo. This will enable present and future managers of the project to master the network thereby facilitating the detection of any malfunctioning for prompt reaction. This simply summarises the putting in place of GIS Applied to Water Supply (GIS-AWS).
基金the National Natural Science Foundation of China(Grant Nos.61673135 and 61603114).
文摘In this paper,the performance of two distinct classes of feedback guidance algorithms is evaluated for a spacecraft rendezvous problem utilizing a continuous low-thrust propulsion system.They are the DG(Differential Geometric)and ZEM/ZEV(Zero-Effort-Miss/Zero-Effort-Velocity)feedback guidance algorithms.Even though these two guidance algorithms do not attempt to minimize the onboard fuel consumption orΔV directly,theΔV requirement is used as a measure of their orbital rendezvous performance for various initial conditions and a wide range of the rendezvous time(within less than one orbital period of the target vehicle).For the DG guidance,the effects of its guidance parameter and terminal time on the closed-loop performance are evaluated by numerical simulations.For the ZEM/ZEV guidance,its nearfuel-optimality is further demonstrated for a rapid,short-range orbital rendezvous,in comparison with the corresponding open-loop optimal solutions.Furthermore,the poorΔV performance of the ZEM/ZEV guidance for a slow,long-range orbital rendezvous is remedied by simply adding an initial drift phase.The ZEM/ZEV feedback guidance algorithm and its appropriate variants are then shown to be a simple practical solution to a non-impulsive rendezvous problem,in comparison with the DG guidance as well as the open-loop optimal guidance.
基金This work was prepared under a research grant from the National Research Foundation of Korea(NRF-2013M1A3A3A02042461)The authors thank the National Research Foundation of Korea for the support of this research work.
文摘This paper investigates a problem of determining the optimal terminal-time or time-to-go of the ZEM/ZEV(Zero-E ort-Miss/Zero-E ort-Velocity)feedback guidance law for a variety of orbital intercept or rendezvous maneuvers.A generalized ZEM/ZEV guidance problem,whose objective is to minimize a combination of the control energy and terminal time,is examined.Algebraic equations whose solution provides the optimal terminal-time of the orbital intercept/rendezvous problems are derived based on the optimal control theory.The e ectiveness of the proposed approach is demonstrated for various orbital maneuver problems.
基金supported by the National Natural Science Foundation of China(11672093)
文摘A conflict of three players, including an attacker, a defender, and a target with bounded control is discussed based on the differential game theories in which the target and the defender use an optimal pursuit strategy. The current approach chooses the miss distance as the outcome of the conflict. Different optimal guidance laws are investigated, and feasible conditions are analyzed for the attacker to accomplish an attacking task. For some given conditions, the attacker cannot intercept the target by only using a one-to-one optimal pursuit guidance law; thus, a guidance law for the attacker to reach a critical safe value is investigated.Specifically, the guidance law is divided into two parts. Before the engagement time between the defender and the attacker, the attacker uses this derived guidance law to guarantee that the evasion distance from the defender is safe, and that the zero-effort-miss(ZEM) distance between the attacker and the target is the smallest.After that engagement time, the attacker uses the optimal one-toone guidance law to accomplish the pursuit task. The advantages and limited conditions of these derived guidance laws are also investigated by using nonlinear simulations.
