Under the demand of strategic air traffic flow management and the concept of trajectory based operations（TBO）,the network-wide 4D flight trajectories planning（N4DFTP） problem has been investigated with the purpose...Under the demand of strategic air traffic flow management and the concept of trajectory based operations（TBO）,the network-wide 4D flight trajectories planning（N4DFTP） problem has been investigated with the purpose of safely and efficiently allocating 4D trajectories（4DTs）（3D position and time） for all the flights in the whole airway network.Considering that the introduction of large-scale 4DTs inevitably increases the problem complexity,an efficient model for strategiclevel conflict management is developed in this paper.Specifically,a bi-objective N4 DFTP problem that aims to minimize both potential conflicts and the trajectory cost is formulated.In consideration of the large-scale,high-complexity,and multi-objective characteristics of the N4DFTP problem,a multi-objective multi-memetic algorithm（MOMMA） that incorporates an evolutionary global search framework together with three problem-specific local search operators is implemented.It is capable of rapidly and effectively allocating 4DTs via rerouting,target time controlling,and flight level changing.Additionally,to balance the ability of exploitation and exploration of the algorithm,a special hybridization scheme is adopted for the integration of local and global search.Empirical studies using real air traffic data in China with different network complexities show that the proposed MOMMA is effective to solve the N4 DFTP problem.The solutions achieved are competitive for elaborate decision support under a TBO environment.展开更多
Purpose: Web2.0 has facilitated the emergence of mass collaboration. Being a new model of virtual collaboration, mass collaboration has distinct characteristics such as self-organized voluntary participation and many-...Purpose: Web2.0 has facilitated the emergence of mass collaboration. Being a new model of virtual collaboration, mass collaboration has distinct characteristics such as self-organized voluntary participation and many-to-many communications mechanism. Behind the sparking achievements, mass collaboration systems are suffering from high coordination cost, reflecting intense conflict among the participants. This study explains how conflict interacts with its antecedents(participation and task complexity) and decedent(group performance) related to the mass collaboration process.Design/methodology/approach: Theoretical model is built upon literatures. Twenty-six measurable items, including social network indices used to reflect conflicts(e.g., density and degree), are extracted from Wikipedia database. The structural equation modeling is used to validate the proposed model.Findings: Participation increases task complexity, conflict and performance; task complexity and conflict increase group performance, but task complexity decreases conflict.Research limitations: This study is limited to one mass collaboration platform, other contexts can cause variance in the result. More characteristics of conflict network(e.g., self-loop)should be taken into consideration in future studies.Practical implications: Conflict management is critical to mass collaboration, and functions that increase the awareness of conflict may motivate users to participant, resulting better group performance.Originality/value: Few studies have investigated the consequences of conflict in mass collaboration context. Meanwhile, limited number of social network studies build network based on negative link. Moreover, most of extant studies on Wiki are descriptive researches without theoretical model. This study builds a theoretical model and incorporates social network approach to explore the influence of conflict.展开更多
Modern day products are usually designed cooperatively by groups of experts, each with his own areas of expertise. Because of different viewpoint, evaluation standard and domain knowledge of these design groups in col...Modern day products are usually designed cooperatively by groups of experts, each with his own areas of expertise. Because of different viewpoint, evaluation standard and domain knowledge of these design groups in collaborative design system, conflict is unavoidable. In this paper, an integration conflict management system (ICMS) was presented from the aspect of all life cycle. A hierarchical constraint network was introduced to detect the conflicts. Three conflict types were classified in ICMS and different type of conflict was submitted to different resolution strategy, constraint relaxation to data conflict and knowlegdge based reasoning to knowledge conflict or schema conflict. To those conflicts hard to be resolved with the above two strategies, an arbitration was used for the conflict resolution. ICMS also provided interface with other collaborative systems such as CAE, CAD to improve the efficiency of collaborative design system.展开更多
A multiple access protocol is proposed to greatly improve multiple access performance of wireless networks with long propagation delay. All the nodes with packets to send can make rapid successful reservation in acces...A multiple access protocol is proposed to greatly improve multiple access performance of wireless networks with long propagation delay. All the nodes with packets to send can make rapid successful reservation in access reservation mini-slots, which is adaptively adjusted according to current traffic load and idle channel resources. A Central Control Node (CCN) coordinates channel reservation and allocates on-demand channel resources to the successfully accessed nodes on two channels. Each node can employ only one handshake to accomplish each communication session, and transmit one or multiple data packets piggybacked with acknowledgment (ACK) information to one or multiple destination nodes in each frame until the end of their communication sessions, which greatly minimizes the impact of long propagation delay caused by handshakes and improves channel efficiency. Simulation results show that the proposed protocol obviously outperforms the Centralized Scheduling-based Medium Access Control (CSMAC) protocol, especially in the presence of long propagation delay.展开更多
Bayesian network (BN) is a well-accepted framework for representing and inferring uncertain knowledge. As the qualitative abstraction of BN, qualitative probabilistic network (QPN) is introduced for probabilistic infe...Bayesian network (BN) is a well-accepted framework for representing and inferring uncertain knowledge. As the qualitative abstraction of BN, qualitative probabilistic network (QPN) is introduced for probabilistic inferences in a qualitative way. With much higher efficiency of inferences, QPNs are more suitable for real-time applications than BNs. However, the high abstraction level brings some inference conflicts and tends to pose a major obstacle to their applications. In order to eliminate the inference conflicts of QPN, in this paper, we begin by extending the QPN by adding a mutual-information-based weight (MI weight) to each qualitative influence in the QPN. The extended QPN is called MI-QPN. After obtaining the MI weights from the corresponding BN, we discuss the symmetry, transitivity and composition properties of the qualitative influences. Then we extend the general inference algorithm to implement the conflict-free inferences of MI-QPN. The feasibility of our method is verified by the results of the experiment.展开更多
基金co-supported by the National Science Foundation for Young Scientists of China(No.61401011)the National Key Technologies R&D Program of China(No.2015BAG15B01)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(No.61521091)
文摘Under the demand of strategic air traffic flow management and the concept of trajectory based operations（TBO）,the network-wide 4D flight trajectories planning（N4DFTP） problem has been investigated with the purpose of safely and efficiently allocating 4D trajectories（4DTs）（3D position and time） for all the flights in the whole airway network.Considering that the introduction of large-scale 4DTs inevitably increases the problem complexity,an efficient model for strategiclevel conflict management is developed in this paper.Specifically,a bi-objective N4 DFTP problem that aims to minimize both potential conflicts and the trajectory cost is formulated.In consideration of the large-scale,high-complexity,and multi-objective characteristics of the N4DFTP problem,a multi-objective multi-memetic algorithm（MOMMA） that incorporates an evolutionary global search framework together with three problem-specific local search operators is implemented.It is capable of rapidly and effectively allocating 4DTs via rerouting,target time controlling,and flight level changing.Additionally,to balance the ability of exploitation and exploration of the algorithm,a special hybridization scheme is adopted for the integration of local and global search.Empirical studies using real air traffic data in China with different network complexities show that the proposed MOMMA is effective to solve the N4 DFTP problem.The solutions achieved are competitive for elaborate decision support under a TBO environment.
基金supported by the Chinese Social Science Foundation(Grant No.10ATQ004)the Graduate Student Innovation Project of Jiangsu Province,China(Grant No.CX10B_022R)
文摘Purpose: Web2.0 has facilitated the emergence of mass collaboration. Being a new model of virtual collaboration, mass collaboration has distinct characteristics such as self-organized voluntary participation and many-to-many communications mechanism. Behind the sparking achievements, mass collaboration systems are suffering from high coordination cost, reflecting intense conflict among the participants. This study explains how conflict interacts with its antecedents(participation and task complexity) and decedent(group performance) related to the mass collaboration process.Design/methodology/approach: Theoretical model is built upon literatures. Twenty-six measurable items, including social network indices used to reflect conflicts(e.g., density and degree), are extracted from Wikipedia database. The structural equation modeling is used to validate the proposed model.Findings: Participation increases task complexity, conflict and performance; task complexity and conflict increase group performance, but task complexity decreases conflict.Research limitations: This study is limited to one mass collaboration platform, other contexts can cause variance in the result. More characteristics of conflict network(e.g., self-loop)should be taken into consideration in future studies.Practical implications: Conflict management is critical to mass collaboration, and functions that increase the awareness of conflict may motivate users to participant, resulting better group performance.Originality/value: Few studies have investigated the consequences of conflict in mass collaboration context. Meanwhile, limited number of social network studies build network based on negative link. Moreover, most of extant studies on Wiki are descriptive researches without theoretical model. This study builds a theoretical model and incorporates social network approach to explore the influence of conflict.
文摘Modern day products are usually designed cooperatively by groups of experts, each with his own areas of expertise. Because of different viewpoint, evaluation standard and domain knowledge of these design groups in collaborative design system, conflict is unavoidable. In this paper, an integration conflict management system (ICMS) was presented from the aspect of all life cycle. A hierarchical constraint network was introduced to detect the conflicts. Three conflict types were classified in ICMS and different type of conflict was submitted to different resolution strategy, constraint relaxation to data conflict and knowlegdge based reasoning to knowledge conflict or schema conflict. To those conflicts hard to be resolved with the above two strategies, an arbitration was used for the conflict resolution. ICMS also provided interface with other collaborative systems such as CAE, CAD to improve the efficiency of collaborative design system.
基金supported by National Science Foundation for Innovative Research Groups of China under Grant No.60921001National Natural Science Foundation of China under Grant No.60933012+2 种基金National Science and Technology Major Project of China under Grant No.2009ZX03006-001-003, 2010ZX03003-003-03China Fundamental Research Funds for the Central Universities under Grant No.YWF-10-01-A16NSBS Program of Beihang University,China under Grant No.221235
文摘A multiple access protocol is proposed to greatly improve multiple access performance of wireless networks with long propagation delay. All the nodes with packets to send can make rapid successful reservation in access reservation mini-slots, which is adaptively adjusted according to current traffic load and idle channel resources. A Central Control Node (CCN) coordinates channel reservation and allocates on-demand channel resources to the successfully accessed nodes on two channels. Each node can employ only one handshake to accomplish each communication session, and transmit one or multiple data packets piggybacked with acknowledgment (ACK) information to one or multiple destination nodes in each frame until the end of their communication sessions, which greatly minimizes the impact of long propagation delay caused by handshakes and improves channel efficiency. Simulation results show that the proposed protocol obviously outperforms the Centralized Scheduling-based Medium Access Control (CSMAC) protocol, especially in the presence of long propagation delay.
文摘Bayesian network (BN) is a well-accepted framework for representing and inferring uncertain knowledge. As the qualitative abstraction of BN, qualitative probabilistic network (QPN) is introduced for probabilistic inferences in a qualitative way. With much higher efficiency of inferences, QPNs are more suitable for real-time applications than BNs. However, the high abstraction level brings some inference conflicts and tends to pose a major obstacle to their applications. In order to eliminate the inference conflicts of QPN, in this paper, we begin by extending the QPN by adding a mutual-information-based weight (MI weight) to each qualitative influence in the QPN. The extended QPN is called MI-QPN. After obtaining the MI weights from the corresponding BN, we discuss the symmetry, transitivity and composition properties of the qualitative influences. Then we extend the general inference algorithm to implement the conflict-free inferences of MI-QPN. The feasibility of our method is verified by the results of the experiment.
