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Hybrid NSGA-Ⅱ for vehicle routing problem with multi-trip pickup and delivery
Jianqiang LI, Zhou HE
Journal of Computer Applications    2024, 44 (4): 1187-1194.   DOI: 10.11772/j.issn.1001-9081.2023101512
Abstract65)   HTML1)    PDF (1477KB)(75)       Save

Concerning the trade-off between convergence and diversity in solving the multi-trip pickup and delivery Vehicle Routing Problem (VRP), a hybrid Non-dominated Sorting Genetic Algorithm Ⅱ (NSGA-Ⅱ) combining Adaptive Large Neighborhood Search (ALNS) algorithm and Adaptive Neighborhood Selection (ANS), called NSGA-Ⅱ-ALNS-ANS, was proposed. Firstly, considering the influence of the initial population on the convergence speed of the algorithm, an improved regret insertion method was employed to obtain high-quality initial population. Secondly, to improve global and local search capabilities of the algorithm, various destroy-repair operators and neighborhood structures were designed, according to the characteristics of the pickup and delivery problem. Finally, a Best Fit Decreasing (BFD) algorithm based on random sampling and an efficient feasible solution evaluation criterion were proposed to generate vehicle routing schemes. The simulation experiments were conducted on public benchmark instances of different scales, in the comparison experiments with the MA (Memetic Algorithm), the optimal solution quality of the proposed algorithm increased by 27%. The experimental results show that the proposed algorithm can rapidly generate high-quality vehicle routing schemes that satisfy multiple constraints, and outperform the existing algorithms in terms of both convergence and diversity.

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New mechanism of realizing time-synchronization in LAN based on data link layer
Hua-jin CHEN Jia-zhou HE
Journal of Computer Applications    2010, 30 (05): 1183-1187.  
Abstract231)      PDF (801KB)(945)       Save
The precision of the common network time protocol is low when being realized in the application layer, while high in physical layer yet a definite hardware is in need. With reference to the WinPcap time stamps management method of the famous network packet pawing software, a new high precision relative time synchronization algorithm was implemented with pure software in data link layer. Besides, the software was tested under Windows XP circumstance in an abbreviated LAN. The result indicates that the proposed algorithm can attain synchronization precision within 100μs.
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New mechanism of realizing time-synchronization in LAN by using CPU time stamp
Hua-jin CHEN Shuang-xi LUO Jia-zhou HE
Journal of Computer Applications    2009, 29 (11): 2920-2924.  
Abstract1877)      PDF (1075KB)(1372)       Save
Currently, many computers are required to cooperate frequently in the network application. Therefore, a uniform clock is in need. A new mechanism to realize clock synchronization in LAN by using CPU internal high-precision time stamp was presented; besides, the server and client software was also developed in VC++, and tested under Windows XP and Windows 2000 circumstance in an abbreviated LAN. The result indicates that the algorithm can attain much high synchronization precision, and the system runs steadily.
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