基于覆盖网络的海上信息栅格无线传输系统研究

文章在通信资源的形式化描述基础上,设计了一种信息栅格的传输体系,为一体化信息系统提供透明的传输服务。针对多重网络传输服务与网络性能的多样性,提出了一种基于作战任务的层次覆盖网络模型,以及实现网络负载均衡的QoS路由算法。     

Energy optimal spacecraft attitude control subject to convergence rate constraints

Attitude control of operational satellites is still predominantly performed by standard controllers such as Proportional plus Derivative (PD) control laws, which are still preferred for implementation to the computationally intensive nonlinear optimal control techniques, representing higher implementation complexity. In this paper, an inverse optimal control approach based on phase space geometry is presented, which is easy to implement and free from numerical and computational issues. The optimal control objective is to minimize a norm of the control torque subject to a rapidity constraint on the convergence rate of a Lyapunov function, under the effect of a benchmark controller. The proposed optimization method is shown to significantly enhance the torque-rapidity trade-off compared to the benchmark controller, chosen to be a PD law then a sliding mode controller. The inverse optimal control scheme is implemented on an air bearing table experimental platform.     

无线Mesh网络负载均衡路由协议

提出一种多路径路由协议CLBRP。CLBRP协议通过分析MAC层帧传输情况实时评判各条路径的质量,从而进行合理的流量分配,对网络拥塞做出迅速有效的反应。在NS2平台上实现CLBRP协议并与其他路由协议进行性能对比,实验结果表明,CLBRP在网络整体负载均衡、拥塞避免、终端业务延迟、终端业务公平性等方面均有较好表现。     

基于障碍物群的k全局相异最优有序路径查询

提出障碍k全局相异最优有序路径的查询问题,利用可视图的思想给出近似查询算法,通过作用集与障碍角度点的引入有效地减少构造可视图障碍对象的数量,分析查询点和数据点构成的线段与可视图的顶点和弧的关系,减少内部障碍路径的计算次数,实现算法的全面优化。实验结果表明,该算法具有较好的性能。     

Optimal search path for service in the presence of disruptions

We consider the following basic search path problem: a customer residing at a node of a network needs to obtain service from one of the facilities; facility locations are known and fixed. Facilities may become inoperational with certain probability; the state of the facility only becomes known when the facility is visited. Customer travel stops when the first operational facility is found. The objective is to minimize the expected total travel distance.     

Numerical inversions of a source term in the FADE with a Dirichlet boundary condition using final observations

This paper deals with an inverse problem of determining a source term in the one-dimensional fractional advection-dispersion equation (FADE) with a Dirichlet boundary condition on a finite domain, using final observations. On the basis of the shifted Grünwald formula, a finite difference scheme for the forward problem of the FADE is given, by means of which the source magnitude depending upon the space variable is reconstructed numerically by applying an optimal perturbation regularization algorithm. Numerical inversions with noisy data are carried out for the unknowns taking three functional forms: polynomials, trigonometric functions and index functions. The reconstruction results show that the inversion algorithm is efficient for the inverse problem of determining source terms in a FADE, and the algorithm is also stable for additional data having random noises.     

Reliability analysis and optimal version-updating for open source software

Context

Although reliability is a major concern of most open source projects, research on this problem has attracted attention only recently. In addition, the optimal version-dating for open source software considering its special properties is not yet discussed.

Objective

In this paper, the reliability analysis and optimal version-updating for open source software are studied.

Method

A modified non-homogeneous Poisson process model is developed for open source software reliability modeling and analysis. Based on this model, optimal version-updating for open source software is investigated as well. In the decision process, the rapid release strategy and the level of reliability are the two most important factors. However, they are essentially contradicting with each other. In order to consider these two conflicting factors simultaneously, a new decision model based on multi-attribute utility theory is proposed.

Results

Our models are tested on the real world data sets from two famous open source projects: Apache and GNOME. It is found that traditional software reliability models provide overestimations of the reliability of open source software. In addition, the proposed decision model can help management to make a rational decision on the optimal version-updating for open source software.

Conclusion

Empirical results reveal that the proposed model for open source software reliability can describe the failure process more accurately. Furthermore, it can be seen that the proposed decision model can assist management to appropriately determine the optimal version-update time for open source software.     

Solving nonlinear optimal control problems using a hybrid IPSO-SQP algorithm

A hybrid algorithm by integrating an improved particle swarm optimization (IPSO) with successive quadratic programming (SQP), namely IPSO-SQP, is proposed for solving nonlinear optimal control problems. The particle swarm optimization (PSO) is showed to converge rapidly to a near optimum solution, but the search process will become very slow around global optimum. On the contrary, the ability of SQP is weak to escape local optimum but can achieve faster convergent speed around global optimum and the convergent accuracy can be higher. Hence, in the proposed method, at the beginning stage of search process, a PSO algorithm is employed to find a near optimum solution. In this case, an improved PSO (IPSO) algorithm is used to enhance global search ability and convergence speed of algorithm. When the change in fitness value is smaller than a predefined value, the searching process is switched to SQP to accelerate the search process and find an accurate solution. In this way, this hybrid algorithm may find an optimum solution more accurately. To validate the performance of the proposed IPSO-SQP approach, it is evaluated on two optimal control problems. Results show that the performance of the proposed algorithm is satisfactory.     

An approach for temporal analysis of email data based on segmentation

Many kinds of information are hidden in email data, such as the information being exchanged, the time of exchange, and the user IDs participating in the exchange. Analyzing the email data can reveal valuable information about the social networks of a single user or multiple users, the topics being discussed, and so on. In this paper, we describe a novel approach for temporally analyzing the communication patterns embedded in email data based on time series segmentation. The approach computes egocentric communication patterns of a single user, as well as sociocentric communication patterns involving multiple users. Time series segmentation is used to uncover patterns that may span multiple time points and to study how these patterns change over time. To find egocentric patterns, the email communication of a user is represented as an item-set time series. An optimal segmentation of the item-set time series is constructed, from which patterns are extracted. To find sociocentric patterns, the email data is represented as an item-setgroup time series. Patterns involving multiple users are then extracted from an optimal segmentation of the item-setgroup time series. The proposed approach is applied to the Enron email data set, which produced very promising results.     

支持普适服务的新一代网络传输层构架

新一代网络没有准确定义,但普遍共识是提供全分组网络和普适服务.其中分组网络一般认为采用IP分组,但普适服务仍不清晰.3G、4G中称"泛在服务";NGI、NGN中强调无缝融合电信网和互联网服务;计算机界类似的概念是"普适计算";IEEE普适服务会议汇聚各种思想,首次提出了"普适服务"的模糊概念.虽然上述研究对普适服务的定义并不统一,但普遍共识是:多样化的服务种类、多样化的网络接入.文中分析传输层在新一代网络设计中的重要地位,以提供普适服务为目标,通过多连接抽象表示服务多样化、多路径抽象表示接入多样化,给出符合新一代网络要求的传输层构架.基于这一构架,可以提高网络的QoS支持、安全可靠性、移动性、可控可管性.文中通过理论分析和原型实现证明了新构架的正确性和可行性.