A multistage amplifier system based on high-power end-pumped two-segmented Nd:YVO4is developed,which realizes the effective beam quality management in high-power lasers.Because of the severe thermal effect caused by h...A multistage amplifier system based on high-power end-pumped two-segmented Nd:YVO4is developed,which realizes the effective beam quality management in high-power lasers.Because of the severe thermal effect caused by high-power end pumping,both the appropriate crystal and beam filling factor(the ratio of the laser beam radius to the pump beam radius)are important in the amplifier.The multisegmented doped crystal is controlled in cooperation with the beam filling factor to realize high output power and maintain good beam quality.To study the thermal effect in the end-pumped crystal,the temperature distributions of end-pumped single-segmented and two-segmented Nd:YVO4are theoretically calculated.In the experiment,a probe laser is employed to measure the spherical aberration coefficient and the beam quality of the laser at the rear end of the two end-pumped crystals,respectively,and the experimental results are in good agreement with the theoretical results.In the power amplification,a seed laser is employed in the experiment.The appropriate gain medium and beam filling factor are determined by considering the spherical aberration coefficient,beam quality,and power extraction efficiency.Based on the reasonable layout of the power amplification for each stage amplifier,the multistage amplifier system outputs a 280.2 W picosecond laser with the beam quality factors of M_(x)^(2)=1.28 and M_(y)^(2)=1.32.展开更多
战场路径规划属于现代军事行动战场指挥的关键决策环节。针对战场路径规划问题,设计了一种基于A^(*)算法与遴荐策略星鸦优化算法(Nutcracker Optimization Algorithm with Recommendation and A^(*)Algorithm based on Fusion,RNOA-A^(...战场路径规划属于现代军事行动战场指挥的关键决策环节。针对战场路径规划问题,设计了一种基于A^(*)算法与遴荐策略星鸦优化算法(Nutcracker Optimization Algorithm with Recommendation and A^(*)Algorithm based on Fusion,RNOA-A^(*))的人机双段路径规划模型。首先,提出了一种人机双段路径规划算法模型,将路径规划区域分为无人机协同区域和自主规划区域。其次,提出了一种区域破障规划模型,根据敌方阵地威胁最大范围找出不规则自主规划区域范围和低威胁破障点。最后,提出了一种基于遴荐策略的星鸦优化算法,挑选出优质星鸦个体位置。仿真结果表明,在相同的迭代次数下,遴荐策略使原算法提高了16.31%的收敛精度,在解决人机双段路径规划问题上,能够规划出由起点至终点的更合理有效的路径方案。展开更多
目的比较颈前路椎间盘切除融合(anterior cervical discectomy with fusion,ACDF)术与颈前路椎体次全切减压融合(anterior cervical corpectomy with fusion,ACCF)术治疗相邻两节段脊髓型颈椎病患者的临床疗效。方法选取2019年8月至2022...目的比较颈前路椎间盘切除融合(anterior cervical discectomy with fusion,ACDF)术与颈前路椎体次全切减压融合(anterior cervical corpectomy with fusion,ACCF)术治疗相邻两节段脊髓型颈椎病患者的临床疗效。方法选取2019年8月至2022年8月西藏军区总医院收治的70例相邻两节段脊髓型颈椎病患者作为研究对象,按照不同手术方式分为甲组与乙组,每组35例。甲组采取ACDF术治疗,乙组采取ACCF术治疗,比较两组手术相关指标、颈椎融合节段Cobb角和颈椎曲度、术后并发症发生情况、颈椎日本骨科协会(Japanese Orthopedic Association,JOA)评分。结果甲组手术时间长于乙组,术中出血量少于乙组,差异有统计学意义(P<0.05);术后12个月,两组颈椎融合节段Cobb角、颈椎曲度均大于术前,且甲组大于乙组,差异有统计学意义(P<0.05);两组术后并发症发生率比较差异无统计学意义;术后6个月,两组颈椎JOA评分均高于术前,差异有统计学意义(P<0.05),但两组间比较差异无统计学意义。结论ACDF、ACCF术治疗相邻两节段脊髓型颈椎病的安全性及术后颈椎功能恢复效果相当,但ACDF术可明显改善患者颈椎融合节段Cobb角、颈椎曲度,减少术中出血量,而ACCF术手术时间更短,临床可酌情选择术式。展开更多
基金supported by the National Natural Science Foundation of China(No.62105179)the National Key R&D Program of China(No.2023YFE0199000)the Baima Lake Laboratory Joint Funds of the Zhejiang Provincial Natural Science Foundation of China(No.LBMHZ24F050001)。
文摘A multistage amplifier system based on high-power end-pumped two-segmented Nd:YVO4is developed,which realizes the effective beam quality management in high-power lasers.Because of the severe thermal effect caused by high-power end pumping,both the appropriate crystal and beam filling factor(the ratio of the laser beam radius to the pump beam radius)are important in the amplifier.The multisegmented doped crystal is controlled in cooperation with the beam filling factor to realize high output power and maintain good beam quality.To study the thermal effect in the end-pumped crystal,the temperature distributions of end-pumped single-segmented and two-segmented Nd:YVO4are theoretically calculated.In the experiment,a probe laser is employed to measure the spherical aberration coefficient and the beam quality of the laser at the rear end of the two end-pumped crystals,respectively,and the experimental results are in good agreement with the theoretical results.In the power amplification,a seed laser is employed in the experiment.The appropriate gain medium and beam filling factor are determined by considering the spherical aberration coefficient,beam quality,and power extraction efficiency.Based on the reasonable layout of the power amplification for each stage amplifier,the multistage amplifier system outputs a 280.2 W picosecond laser with the beam quality factors of M_(x)^(2)=1.28 and M_(y)^(2)=1.32.
文摘战场路径规划属于现代军事行动战场指挥的关键决策环节。针对战场路径规划问题,设计了一种基于A^(*)算法与遴荐策略星鸦优化算法(Nutcracker Optimization Algorithm with Recommendation and A^(*)Algorithm based on Fusion,RNOA-A^(*))的人机双段路径规划模型。首先,提出了一种人机双段路径规划算法模型,将路径规划区域分为无人机协同区域和自主规划区域。其次,提出了一种区域破障规划模型,根据敌方阵地威胁最大范围找出不规则自主规划区域范围和低威胁破障点。最后,提出了一种基于遴荐策略的星鸦优化算法,挑选出优质星鸦个体位置。仿真结果表明,在相同的迭代次数下,遴荐策略使原算法提高了16.31%的收敛精度,在解决人机双段路径规划问题上,能够规划出由起点至终点的更合理有效的路径方案。
