研究了带时间窗多车场车辆路径问题(multi-depots vehicle routing problem with time windows,MDVRPTW),建立MDVRPTW模型,设计了结合混合高斯模型(Gaussian mixture model,GMM)聚类算法的自适应大邻域搜索(adaptive large neighborhood...研究了带时间窗多车场车辆路径问题(multi-depots vehicle routing problem with time windows,MDVRPTW),建立MDVRPTW模型,设计了结合混合高斯模型(Gaussian mixture model,GMM)聚类算法的自适应大邻域搜索(adaptive large neighborhood search,ALNS)算法。通过在邻域变换前将客户集进行分类,优化初始解,提高算法运算效率。算法使用6种不同变换因子,采用得分系统对变换因子进行评价,使算法能够在迭代的不同阶段自适应地选择合适的变换因子。分析了参数设置值的合理性,设计了3组仿真实验,实验结果验证了算法的高效性。展开更多
In recent years,Unmarred Aerial Vehicles(UAVs)have been extensively employed for reconnaissance missions.Our focus is prioritizing reconnaissance of high-priority targets while minimizing the flight duration when UAV ...In recent years,Unmarred Aerial Vehicles(UAVs)have been extensively employed for reconnaissance missions.Our focus is prioritizing reconnaissance of high-priority targets while minimizing the flight duration when UAV power is constrained.We introduce a framework,which integrates Deep-Q Network(DQN)into the Adaptive Large Neighborhood Search(ALNS)metaheuristic algorithm,called DQN-ALNS,to optimize the process through the current solution’s search state.Specifically,the agent is utilized to select the destroy-repair operators to update a new solution,thereby iteratively optimizing the UAV reconnaissance routes.Experimental results reveal that DQN-ALNS achieves superior solutions and faster convergence than other comparison algorithms.The algorithm leverages the exploratory potential of the current solution and demonstrates robust stability.The final sensitivity analysis showcases that reconnaissance missions with high priority are better accomplished when the UAV power is moderate and the target priority is concentrated at smaller values.展开更多
High-temperature-annealed Al N(HTA-Al N) templates provide ideal substrates for high-quality Al Ga N epitaxy. However, the significant compressive stress accumulated within the Al Ga N layer makes it challenging to ac...High-temperature-annealed Al N(HTA-Al N) templates provide ideal substrates for high-quality Al Ga N epitaxy. However, the significant compressive stress accumulated within the Al Ga N layer makes it challenging to achieve a smooth surface free of hexagonal hillocks on these templates. To address this issue, we investigate the mechanism of compressive stress accumulation during the growth of Al Ga N-based epilayers on HTA-Al N templates using in-situ curvature analysis in this study. To verify the mechanism, a low-Al-content Al Ga N interlayer is introduced between the Al N epilayer and the subsequent Al Ga N epilayer. The larger a-plane lattice constant of this interlayer relative to the Al Ga N epilayer slows the accumulation rate of compressive stress. The hexagonal hillock can be effectively suppressed and the surface of Al Ga N epilayer can be significantly regulated by adopting various low-Al-content Al Ga N interlayers. This work provides a comprehension on the stress accumulation mechanism in Al Ga N epilayers and a feasible method to obtain hillock-free surface of Al Ga N epilayers on HTA-Al N templates,which will be beneficial for fabricating Al Ga N based devices.展开更多
氮化铝镓(AlGaN)与氮化铝(AlN)属于第三代半导体材料,广泛应用于发光二极管(LED)和功率电子器件领域。金属有机化学气相沉积(Metal-organic Chemical Vapor Deposition,MOCVD)是制备这些半导体材料的关键。当应用预混喷淋式MOCVD时,在...氮化铝镓(AlGaN)与氮化铝(AlN)属于第三代半导体材料,广泛应用于发光二极管(LED)和功率电子器件领域。金属有机化学气相沉积(Metal-organic Chemical Vapor Deposition,MOCVD)是制备这些半导体材料的关键。当应用预混喷淋式MOCVD时,在高温条件下,预反应会对薄膜的均匀性产生不利影响,降低混合腔的温度可以解决这个问题。对混合腔下盘、喷淋口上盘和盘体组成的通道进行冷却,可以使混合腔处于低温状态。笔者对原有冷却通道进行分析,发现温度分布均匀性较差。为了解决以上问题,本文提出多扇区通道冷却和多平行通道冷却方式,研究结果表明,八扇区B模型可以更好地冷却混合腔,冷却均匀性更高。展开更多
The rapid evolution of unmanned aerial vehicle(UAV)technology and autonomous capabilities has positioned UAV as promising last-mile delivery means.Vehicle and onboard UAV collaborative delivery is introduced as a nove...The rapid evolution of unmanned aerial vehicle(UAV)technology and autonomous capabilities has positioned UAV as promising last-mile delivery means.Vehicle and onboard UAV collaborative delivery is introduced as a novel delivery mode.Spatiotemporal collaboration,along with energy consumption with payload and wind conditions play important roles in delivery route planning.This paper introduces the traveling salesman problem with time window and onboard UAV(TSPTWOUAV)and emphasizes the consideration of real-world scenarios,focusing on time collaboration and energy consumption with wind and payload.To address this,a mixed integer linear programming(MILP)model is formulated to minimize the energy consumption costs of vehicle and UAV.Furthermore,an adaptive large neighborhood search(ALNS)algorithm is applied to identify high-quality solutions efficiently.The effectiveness of the proposed model and algorithm is validated through numerical tests on real geographic instances and sensitivity analysis of key parameters is conducted.展开更多
文摘研究了带时间窗多车场车辆路径问题(multi-depots vehicle routing problem with time windows,MDVRPTW),建立MDVRPTW模型,设计了结合混合高斯模型(Gaussian mixture model,GMM)聚类算法的自适应大邻域搜索(adaptive large neighborhood search,ALNS)算法。通过在邻域变换前将客户集进行分类,优化初始解,提高算法运算效率。算法使用6种不同变换因子,采用得分系统对变换因子进行评价,使算法能够在迭代的不同阶段自适应地选择合适的变换因子。分析了参数设置值的合理性,设计了3组仿真实验,实验结果验证了算法的高效性。
基金supported by the National Natural Science Foundation of China(Nos.72271241 and 72301290)the Hunan Key Laboratory of Intelligent Decision-Making Technology for Emergency Management(No.2020TP1013).
文摘In recent years,Unmarred Aerial Vehicles(UAVs)have been extensively employed for reconnaissance missions.Our focus is prioritizing reconnaissance of high-priority targets while minimizing the flight duration when UAV power is constrained.We introduce a framework,which integrates Deep-Q Network(DQN)into the Adaptive Large Neighborhood Search(ALNS)metaheuristic algorithm,called DQN-ALNS,to optimize the process through the current solution’s search state.Specifically,the agent is utilized to select the destroy-repair operators to update a new solution,thereby iteratively optimizing the UAV reconnaissance routes.Experimental results reveal that DQN-ALNS achieves superior solutions and faster convergence than other comparison algorithms.The algorithm leverages the exploratory potential of the current solution and demonstrates robust stability.The final sensitivity analysis showcases that reconnaissance missions with high priority are better accomplished when the UAV power is moderate and the target priority is concentrated at smaller values.
基金supported by the National Key R&D Program of China (Grant No. 2022YFB3605000)the National Natural Science Foundation of China (Nos. 62004127, 61725403, 62121005, 61922078, 61827813, and 62004196)+1 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciencesthe Youth Talent Promotion Project of the Chinese Institute of Electronics (No. 2020QNRC001)。
文摘High-temperature-annealed Al N(HTA-Al N) templates provide ideal substrates for high-quality Al Ga N epitaxy. However, the significant compressive stress accumulated within the Al Ga N layer makes it challenging to achieve a smooth surface free of hexagonal hillocks on these templates. To address this issue, we investigate the mechanism of compressive stress accumulation during the growth of Al Ga N-based epilayers on HTA-Al N templates using in-situ curvature analysis in this study. To verify the mechanism, a low-Al-content Al Ga N interlayer is introduced between the Al N epilayer and the subsequent Al Ga N epilayer. The larger a-plane lattice constant of this interlayer relative to the Al Ga N epilayer slows the accumulation rate of compressive stress. The hexagonal hillock can be effectively suppressed and the surface of Al Ga N epilayer can be significantly regulated by adopting various low-Al-content Al Ga N interlayers. This work provides a comprehension on the stress accumulation mechanism in Al Ga N epilayers and a feasible method to obtain hillock-free surface of Al Ga N epilayers on HTA-Al N templates,which will be beneficial for fabricating Al Ga N based devices.
文摘氮化铝镓(AlGaN)与氮化铝(AlN)属于第三代半导体材料,广泛应用于发光二极管(LED)和功率电子器件领域。金属有机化学气相沉积(Metal-organic Chemical Vapor Deposition,MOCVD)是制备这些半导体材料的关键。当应用预混喷淋式MOCVD时,在高温条件下,预反应会对薄膜的均匀性产生不利影响,降低混合腔的温度可以解决这个问题。对混合腔下盘、喷淋口上盘和盘体组成的通道进行冷却,可以使混合腔处于低温状态。笔者对原有冷却通道进行分析,发现温度分布均匀性较差。为了解决以上问题,本文提出多扇区通道冷却和多平行通道冷却方式,研究结果表明,八扇区B模型可以更好地冷却混合腔,冷却均匀性更高。
基金Fundamental Research Funds for the Central Universities(2024JBZX038)National Natural Science F oundation of China(62076023)。
文摘The rapid evolution of unmanned aerial vehicle(UAV)technology and autonomous capabilities has positioned UAV as promising last-mile delivery means.Vehicle and onboard UAV collaborative delivery is introduced as a novel delivery mode.Spatiotemporal collaboration,along with energy consumption with payload and wind conditions play important roles in delivery route planning.This paper introduces the traveling salesman problem with time window and onboard UAV(TSPTWOUAV)and emphasizes the consideration of real-world scenarios,focusing on time collaboration and energy consumption with wind and payload.To address this,a mixed integer linear programming(MILP)model is formulated to minimize the energy consumption costs of vehicle and UAV.Furthermore,an adaptive large neighborhood search(ALNS)algorithm is applied to identify high-quality solutions efficiently.The effectiveness of the proposed model and algorithm is validated through numerical tests on real geographic instances and sensitivity analysis of key parameters is conducted.
