排序方式: 共有11条查询结果,搜索用时 109 毫秒
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选取2009-2018年中国30个省(市、自治区)的数据,运用区位商相对差异指数和熵权TOPSIS法分别测算其产业协同集聚度和区域创新水平,研究二三产业协同集聚对区域创新的影响.研究表明:产业集聚通过“知识技术、劳动力、物力”等外部规模经济增加创新产出;2009-2018年,两产业协同集聚水平由中西部向东部递减,区域创... 相似文献
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邓晶刘倩 《数学的实践与认识》2022,(11):108-121
采用基于DEA的SBM-ML法测算2009-2018年中国其中30个省的绿色全要素生产率,并用熵权TOPSIS法从创新基础,创新投入和创新产出三个维度综合评价了10年30个省的区域创新水平,并通过空间计量模型研究区域创新、财政分权对中国绿色全要素生产率的影响.研究表明:中国绿色全要素生产率水平呈现正向空间集聚特征且东部明显高于中西部,区域创新水平与绿色全要素生产率之间具有非线性关系,并呈倒“U”型分布,地方财政分权与绿色全要素生产率呈负向关系,财政分权对区域创新促进绿色全要素生产率的提高有明显的强化作用,此外,财政分权的作用效果受区域创新水平的影响,当区域创新水平较高时,财政分权对绿色全要素生产率将从抑制作用将转变为促进作用.最后基于结论提出建议. 相似文献
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Design and performance of a composite Tm:YAG laser pumped by VBG-stabilized narrow-band laser diode
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A 2-μm composite Tm:YAG laser pumped with a narrow-band laser diode was presented. The temperature distribution and thermal lens in the Tm:YAG were numerically simulated by a finite element method and the results were used to design the special cavity, in order to achieve a high efficiency and stable output. With a 25-W incident pump power, we obtained a maximum output power of 11 W at 2018.5 nm, corresponding to a slope efficiency of 51.3% and an optical-to-optical efficiency of 44.5%, respectively. The beam quality was measured to be M_x~2= 1.8 and M_y~2= 1.6. 相似文献
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研究了激光二极管端面抽运的双纵模双频微片激光器的热效应对其输出频谱的影响. 通过对端面抽运Nd:YVO4微片的热传导方程求解得出晶体内部的温度场分布; 并进一步对微片晶体热致折射率变化进行分析, 由此计算出双频微片激光器的热致频谱变化. 实验结果表明: 当抽运功率较小时得到稳定的双纵模双频激光输出; 当抽运功率增大时, 晶体热效应使双频激光频谱双峰之间的频差减小, 各纵模波长频谱宽度加宽, 实验结果与理论分析相符合.
关键词:
光载无线通信
双频微片激光器
热效应
频率差 相似文献
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<正>We obtain high peak power pulses in megawatt range of the first(1181 nm),second(1321 nm),and third order(1500 nm) Stokes radiation from self-conversion of the 1067-nm laser radiation based on Nd:KGW laser.The maximum output energy of the first order Stokes laser is 35.3 mJ,which is to our knowledge, the highest reported energy in an intracavity Q-switched laser.The third order Stokes pulse is obtained in an intracavity Q-switched laser. 相似文献
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就硒缺乏症、硒与透析的关系,检查了慢性肾功不全患者血清中的硒,其浓度为9.8±1.9μg/dL,正常人的血清中,硒浓度为13.7±2.6μg/dL.并对慢性肾功不全的患者进行透析,测定其血清中硒浓度为10.7±3.1μg/dL.结果表明:慢性肾功不全患者血清中硒浓度低于正常人血清中画浓度,经透析后血清中硒浓度虽有上升,但仍不如正常人,并且随着透析期间的延长血清中硒浓度逐渐下降. 相似文献
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Development of an injection-seeded single-frequency laser by using the phase modulated technique
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An injection-seeded single-frequency Q-switched Nd:YAG laser is accomplished by using a phase modulated rampfire technique. A RbTiOPO_4(RTP) electro-optic crystal is selected for effective optical path length modulation of the slave self-filtering unstable resonator. This single-frequency laser is capable of producing 50 m J pulse energy at 1 Hz repetition rate with a pulse width of 16 ns. The standard deviation of laser pulse intensity for consecutive 100 shots from the mean pulse intensity is less than 1.05%. A spectral linewidth of less than 0.5 pm with a frequency jitter of about 14 fm over30 min is obtained. 相似文献