用鱼眼镜头获得平顶化聚焦的精细激光束

为了将激光高斯光束转化为精细加工需要的能量集中且均匀分布的平顶聚焦的精细激光束,利用衍射成像及其像差理论研究了具有较大畸变和一定场曲的鱼眼镜头对高斯光束的衍射变换作用,导出了其解析计算式,表明了该鱼眼镜头对高斯光束平顶化聚焦的原理。利用Matlab软件进行计算机模拟实验,展示了该鱼眼镜头对高斯光束的平顶化聚焦效果和容易而精密的可调性,表明这一方法与技术是可行的。用该方法获得的平顶化聚焦的精细激光束可被用于激光精细加工、微光机电系统和医学治疗等领域发挥重要作用。

文昌华侨住宅空间的现代化演变研究

受南洋和港澳地区被殖民统治时期的建筑文化影响,海南文昌华侨住宅从19世纪末到20世纪30年代快速地发生转型,进入现代化演变的进程。与发生在大陆沿海城市的转型不同,文昌华侨住宅的现代化首先由民间自发主导,是中国传统乡村住宅现代化演变的先声和重要样本。文章从住宅空间演变的视角出发,分析了50余处文昌华侨住宅的空间组织和建筑形式,认为文昌侨宅的现代化演变以廊化、平顶化和楼化为主要形式,遵循单体演变和单体组合连接的演变路径。与闽粤华侨住宅相比,文昌华侨住宅的现代化具有立足传统空间形制的共性和合院内廊化的个性,这些特点与当地气候条件和社会环境紧密相关。

基于微小孔径衍射的光纤耦合研究

光纤耦合方式影响光纤耦合效率和信息的完整性,为此研究了基于微小孔径衍射的光纤耦合,从直接耦合、微小圆孔耦合、微小透镜耦合到畸变微小透镜耦合,通过考察束型、强度分布、光斑大小等改变,进而提出了鱼眼镜头光纤耦合方式,获得了平顶化聚焦光斑。计算机模拟实验表明,这种鱼眼镜头耦合方式改善了耦合效能。

利用畸变透镜获得精细加工激光束

为了获得激光精细加工需要的能量集中且均匀分布的平顶聚焦激光束,利用衍射理论研究了畸变透镜对高斯光束衍射变换的作用,导出了解析计算式,进而获知畸变透镜如何对激光束平顶化聚焦的原理。用Matlab软件进行计算模拟,讨论了畸变透镜对高斯光束平顶化聚焦的情形和影响因素。表明利用畸变透镜对高斯光束平顶化聚焦是可行的。用这种方法获得的平顶化聚焦激光束可用于激光精细加工、微光机电系统和医学治疗等领域发挥重要作用。

The Impact of the South Asia High Bimodality on the Chemical Composition of the Upper Troposphere and Lower Stratosphere

The South Asia High （SAH） is the dominant feature of the circulation in the upper troposphere and lower stratosphere （UTLS） during the boreal summer, and the upper tropospheric anticyclonic circulation extends into the lower stratosphere. The preferred locations of the center of the SAH occur in two different regions, and the center can be located over the Iranian Plateau or over the Tibetan Plateau. This bimodality has an impact on the distribution of chemical constituents in the UTLS region. We analyzed water vapor （H20）, carbon monoxide （CO）, and ozone （03） data derived from the Aura Microwave Limb Sounder （MLS） and total column ozone data from the Ozone Monitoring Instrument （OMI）. For the Iranian Plateau mode of the SAH, the tropospheric tracers exhibited a positive anomaly over the Iranian Plateau and a negative anomaly over the Tibetan Plateau, whereas the stratospheric tracer exhibited a negative and a positive anomaly over the Iranian Plateau and the Tibetan Plateau, respectively. For the Tibetan Plateau mode, however, the distribution of the anomaly was the reverse of that found for the chemical species in the UTLS region. Furthermore, the locations of the extrema within the anomaly seemed to differ across chemical species. The anomaly extrema for H20 occurred in the vicinity of the SAH ridgeline, whereas CO and O3 exhibited a northward shift of 4-8 degrees. These impacts of the variation in the SAH on the chemical constitutes in the UTLS region can be attributed in part to the dynamical structure delineated by the tropopause field and the temperature field at 100 hPa.

Sea surface height variations in the Mindanao Dome region in response to the northern tropical Pacific winds

Sea surface height (SSH) variability in the Mindanao Dome (MD) region is found to be one of the strong variations in the northern Pacific. It is only weaker than that in the Kuroshio Extension area, and is comparable to that in the North Pacific Subtropical Countercurrent region. Based on a 1.5-layer reduced gravity model, we analyzed SSH variations in this region and their responses to northern tropical Pacific winds. The average SSH anomaly in the region varies mainly on a seasonal scale, with significant periods of 0.5 and 1 year, ENSO time scale2-7years, and time scale in excess of 8 years. Annual and long-term variabilities are comparably stronger. These variations are essentially a response to the northern tropical Pacific winds. On seasonal and ENSO time scales, they are mainly caused by wind anomalies east of the region, which generate westward-propagating, long Rossby waves. On time scales longer than 8 years, they are mostly induced by local Ekman pumping. Long-term SSH variations in the MD region and their responses to local winds are examined and discussed for the first time .