针对带时间窗的车辆路径问题(Vehicle Routing Problems with Time Windows,VRPTW),提出了一种混合粒子群优化算法(Hybrid Particle Swarm Optimization,HPSO)进行求解。所提出的算法设计了一种高效的编解码策略,以此搭建HPSO算法解空间...针对带时间窗的车辆路径问题(Vehicle Routing Problems with Time Windows,VRPTW),提出了一种混合粒子群优化算法(Hybrid Particle Swarm Optimization,HPSO)进行求解。所提出的算法设计了一种高效的编解码策略,以此搭建HPSO算法解空间到VRPTW解空间的桥梁。同时为了提高算法的寻优能力,设计了由单点插入策略以及双点交换策略组成的局部搜索策略。通过solomon-50标准数据集中的九个算例进行仿真实验,实验结果证明了所提出算法的寻优能力和稳定性均优于对比算法,最优解误差相较于对比算法最多降低了38.32%。展开更多
Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperatur...Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperature is considerably below one femtosecond at high Fourier frequency. The ultrashort pulse train with ultralow timing jitter enables absolute time-of-flight measurements based on a dual-comb implementation, which is typically composed of a pair of optical frequency combs generated by femtosecond lasers. Dead-zone-free absolute distance measurement with sub-micrometer precision and kHz update rate has been routinely achieved with a dual-comb configuration, which is promising for a number of precision manufacturing applications, from large step-structure measurements prevalent in microelectronic profilometry to three coordinate measurements in large-scale aerospace manufacturing and shipbuilding. In this paper, we first review the sub-femtosecond precision timing jitter characterization methods and approaches for ultralow timing jitter mode-locked fiber laser design. Then, we provide an overview of the state-of-the-art dual-comb absolute ranging technology in terms of working principles, experimental implementations, and measurement precisions. Finally, we discuss the impact of quantum-limited timing jitter on the dual-comb ranging precision at a high update rate. The route to highprecision dual-comb range finder design based on ultralow jitter femtosecond fiber lasers is proposed.展开更多
The dropping scales is an important parameter for comber noil and combing quality. Because the rocking of the nipper shaft makes the nippers move backward and forward through a series of links, the original position o...The dropping scales is an important parameter for comber noil and combing quality. Because the rocking of the nipper shaft makes the nippers move backward and forward through a series of links, the original position of nipper frame is altered when changing the dropping scales, the other parameters of combing are changed accordingly. In this paper, the timing of opening-closing on nipper, the timing of cylinder’s combing, the timing of detaching-lapping and variation of nip pressure are calculated and their effects on combing are analyzed in different dropping scales on E7/6 comber.展开更多
High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-...High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-frequency signal,seeking for new time-transfer techniques betw een distant clocks w ith much further improved accuracy attracts attentions w orld-w idely. The time-transfer technique based on optical pulses has the highest precision presently,and the further improvement in the accuracy is heavily dependent on the time-domain properties of the pulse as w ell as the sensitivity of the applied measurement on the exchanged pulse. The application of optical frequency comb in time transfer for a precision up to femtosecond level are currently the focus of much interest,and has recently achieved many breakthroughs. Further investigations show that,utilizing quantum techniques,i.e. quantum measurement technique and quantum optical pulse source,can lead to a new limit on the measured timing information. Furthermore,it can be immune from atmospheric parameters,such as pressure,temperature,humidity and so on.Such quantum improvements on time-transfer have a bright prospect in the future applications requiring extremely high-accuracy timing and ranging. The potential achievements w ill form a technical basis for the future realization of sub-femtosecond time transfer system.展开更多
文摘针对带时间窗的车辆路径问题(Vehicle Routing Problems with Time Windows,VRPTW),提出了一种混合粒子群优化算法(Hybrid Particle Swarm Optimization,HPSO)进行求解。所提出的算法设计了一种高效的编解码策略,以此搭建HPSO算法解空间到VRPTW解空间的桥梁。同时为了提高算法的寻优能力,设计了由单点插入策略以及双点交换策略组成的局部搜索策略。通过solomon-50标准数据集中的九个算例进行仿真实验,实验结果证明了所提出算法的寻优能力和稳定性均优于对比算法,最优解误差相较于对比算法最多降低了38.32%。
基金supported by National Natural Science Foundation of China (Grant Nos.61475162,61675150,and 61535009)Tianjin Natural Science Foundation (Grant No.18JCYBJC16900)Tianjin Research Program of Application Foundation and Advanced Technology (Grant No.17JCJQJC43500)
文摘Passively mode-locked fiber lasers emit femtosecond pulse trains with excellent short-term stability. The quantum-limited timing jitter of a free running femtosecond erbium-doped fiber laser working at room temperature is considerably below one femtosecond at high Fourier frequency. The ultrashort pulse train with ultralow timing jitter enables absolute time-of-flight measurements based on a dual-comb implementation, which is typically composed of a pair of optical frequency combs generated by femtosecond lasers. Dead-zone-free absolute distance measurement with sub-micrometer precision and kHz update rate has been routinely achieved with a dual-comb configuration, which is promising for a number of precision manufacturing applications, from large step-structure measurements prevalent in microelectronic profilometry to three coordinate measurements in large-scale aerospace manufacturing and shipbuilding. In this paper, we first review the sub-femtosecond precision timing jitter characterization methods and approaches for ultralow timing jitter mode-locked fiber laser design. Then, we provide an overview of the state-of-the-art dual-comb absolute ranging technology in terms of working principles, experimental implementations, and measurement precisions. Finally, we discuss the impact of quantum-limited timing jitter on the dual-comb ranging precision at a high update rate. The route to highprecision dual-comb range finder design based on ultralow jitter femtosecond fiber lasers is proposed.
文摘The dropping scales is an important parameter for comber noil and combing quality. Because the rocking of the nipper shaft makes the nippers move backward and forward through a series of links, the original position of nipper frame is altered when changing the dropping scales, the other parameters of combing are changed accordingly. In this paper, the timing of opening-closing on nipper, the timing of cylinder’s combing, the timing of detaching-lapping and variation of nip pressure are calculated and their effects on combing are analyzed in different dropping scales on E7/6 comber.
文摘High-precision time transfer plays an important role in the areas of fundamental research and applications. Accompanying w ith the remarkable improvements in the ability of generating and measuring high-accuracy time-frequency signal,seeking for new time-transfer techniques betw een distant clocks w ith much further improved accuracy attracts attentions w orld-w idely. The time-transfer technique based on optical pulses has the highest precision presently,and the further improvement in the accuracy is heavily dependent on the time-domain properties of the pulse as w ell as the sensitivity of the applied measurement on the exchanged pulse. The application of optical frequency comb in time transfer for a precision up to femtosecond level are currently the focus of much interest,and has recently achieved many breakthroughs. Further investigations show that,utilizing quantum techniques,i.e. quantum measurement technique and quantum optical pulse source,can lead to a new limit on the measured timing information. Furthermore,it can be immune from atmospheric parameters,such as pressure,temperature,humidity and so on.Such quantum improvements on time-transfer have a bright prospect in the future applications requiring extremely high-accuracy timing and ranging. The potential achievements w ill form a technical basis for the future realization of sub-femtosecond time transfer system.
