Online scheduling of distributed Earth observation satellite system under rigid communication constraints

This paper focused on online scheduling of distributed Earth observation satellite system in a dynamic environment. The objective was to maximize the total profit of the overall system by efficiently coordinating the different satellites with stochastic arrival of urgent tasks, subject to rigid communication and observation time window constraints. We formulated this problem as a single-task, single-robot, time-extended assignment problem with intra-schedule dependency using the multi-robot task assignment taxonomy and formulated the sub-problem after releasing urgent tasks in a mixed-integer linear programming model. We first described the online scheduling algorithm for a single satellite, then we proposed the modified consensus-based bundle algorithm (m-CBBA) and modified asynchronous consensus-based bundle algorithm (m-ACBBA) with synchronous and asynchronous communication, respectively. Compared with initial versions of CBBA and ACBBA, the modified versions added the communication loop prediction phases to efficiently utilize scarce communication opportunities and reduce the communication requirements. Additionally, we introduce two contract net protocol (CNP)-based algorithms for comparison, respectively SingleItem-CNP-based (SI-CNP) algorithm and Batch-CNP-based (BA-CNP) algorithm. Computational experiments indicated that both the total profit and percentage of scheduled urgent tasks achieved by the m-ACBBA and m-CBBA algorithms were much higher than those achieved by both SI-CNP and BA-CNP. Additionally, the number of communications needed by either m-ACBBA or m-CBBA algorithm was lower than that by SI-CNP. When the communication cost in the system is high, the m-CBBA algorithm is preferred because it balances the profit and the required number of communications. When the communication cost is low, the m-ACBBA algorithm is preferred because it achieves high total profit and high percentage of scheduled urgent tasks.     

关于复合函数极限几个定理的探讨

本文对复合函数的极限做了细致的讨论，给出了6个定理。     

Air route network optimization in fragmented airspace based on cellular automata

Air route network optimization,one of the essential parts of the airspace planning,is an effective way to optimize airspace resources,increase airspace capacity,and alleviate air traffic con gestion.However,little has been done on the optimization of air route network in the fragmented airspace caused by prohibited,restricted,and dangerous areas (PRDs).In this paper,an air route network optimization model is developed with the total operational cost as the objective function while airspace restriction,air route network capacity,and non-straight-line factors (NSLF) are taken as major constraints.A square grid cellular space,Moore neighbors,a fixed boundary,together with a set of rules for solving the route network optimization model are designed based on cellular automata.The empirical traffic of airports with the largest traffic volume in each of the 9 flight information regions in mainland China is collected as the origin-destination (OD) air port pair demands.Based on traffic patterns,the model generates 35 air routes which successfully avoids 144 PRDs.Compared with the current air route network structure,the number of nodes decreases by 41.67％,while the total length of flight segments and air routes drop by 32.03％ and 5.82％ respectively.The NSLF decreases by 5.82％ with changes in the total length of the air route network.More importantly,the total operational cost of the whole network decreases by 6.22％.The computational results show the potential benefits of the model and the advantage of the algorithm.Optimization of air route network can significantly reduce operational cost while ensuring operation safety.     

基于阻力分解策略的翼型阻力计算方法研究

研究并应用了基于翼型阻力分解策略的中场积分计算阻力的方法。中场积分方法是近年来提出的一种新的计算阻力的方法,方法将流场分为三个不同的区域：波阻区、型阻区、数值耗散区,通过对不同区域进行积分将阻力分解为波阻、型阻、数值耗散阻力。计算结果表明中场积分方法与传统的表面积分方法和远场积分方法相比,不仅可以将阻力分解成不同部分以便于进一步分析阻力产生机理,而且在计算中对网格量的要求较低,即使在网格量较小的情况下也能得到较精确的结果。     

网络时代大学生思想教育面临的挑战与对策

互联网作为当今最具影响力的媒体之一,深刻地影响和改变着人们的工作、生活、学习和思雏方式。在网络时代的冲击和挑战下,大学生思想政治教育面临着很多新问题,要求思想政治教育工作者不断提出新的对策,进一步加强和改进大学生思想政治教育。     

国有企业资产重组中职工带资分流的法律研究

如何做好主辅分离,既加强主业企业的竞争优势,又妥善安置好分流职工,是国有企业资产重组中的一个重要课题。采取职工带资分流的方式,是解决这一难题的一个有效途径。鉴于我国目前在此方面的相关立法并不健全,我国应进一步完善相关立法。