Improvement of photorefractive properties in Hf:Fe:LiNbO₃ crystals with various [Li]/[Nb] ratios     

孙秀冬  石宏新  骆素华  孟庆鑫  姜永远 《海洋学报(英文版)》2010,29(9)

Photorefractive properties of Hf:Fe:LiNbO₃ crystals with various [Li]/[Nb] ratios have been investigated at 488 nm wavelength based on the two-wave coupling experiment. High diffraction efficiency and large recording sensitivity are observed and explained. The decrease in Li vacancies is suggested to be the main contributor to the increase in the photoconductivity and subsequently to the induction of the improvement of recording sensitivity. The saturation diffraction efficiency is measured up to 80.2%, and simultaneously the recording sensitivity of 0.91 cm/J is achieved to in the Hf:Fe:LiNbO₃ crystal grown from the melt with the [Li]/[Nb] ratio of 1.20, which is significantly enhanced as compared with those of the Hf:Fe:LiNbO₃ crystal with the [Li]/[Nb] ratio of 0.94 in melt under the same experimental conditions. Experimental results definitely show that increasing the [Li]/[Nb] ratio in crystal is an effective method for Hf:Fe:LiNbO₃ crystal to improve its photorefractive properties.  相似文献   

一种可考虑历史洪水的马氏权函数法研究   总被引：1，自引：0，他引：1       下载免费PDF全文

陈元芳 《水科学进展》1994,5(3):174-178

导出了非连序样本下,马氏权函数法(适用于P-Ⅲ型分布)参数估计公式.在不偏性、有效性的标准下,统计试验结果表明,推导的非连序样本下的计算公式是较为有效的,且拓宽了马氏权函数法的使用范围.  相似文献   

MODULATION OF ATMOSPHERIC THERMAL AND MECHANICAL FORCINGS AND NUMERICAL MODELING OF MEAN MERIDIONAL CIRCULATION          下载免费PDF全文

Wu Guoxiong  Cai Yaping 《Acta Meteorologica Sinica》1993,7(4):412-422

Upon investigating the relative locations of internal and external forcing and the resultant mean meridional circulation,it was found that thermal forcing and mechanical forcing for the formation of atmospheric mean meridional circulation are modulated by a certain ratio.This ratio is determined by the inherent baroclinity,static stability and absolute vorticity of the atmosphere.By employing a parameterization scheme for radiative heating and condensation heating,together with the analysisdata of the European Center for Medium-range Weather Forecasts,the mean meridional circulation for January wassimulated numerically.It was found that latent heat release in the tropics may result in the formation of double-layeredHadley circulation,so do the eddy momentum transfer processes.On the other hand,mean meridional circulations in extra-tropics are mainly determined by external momentum forcing and atmospheric properties of eddy momentum andheat transfer.  相似文献   

船舶气象导航随船验证     

杨良华 《气象》1993,19(9):52-55

通过横流太平洋往返两个航次随船调查，研究了采用气象导航对减少燃油消耗和保证船舶安全、班期等，不但有定的经济效益，而且是一种非常有效的航运管理方法。  相似文献   

新疆前兆震群ρ值的研究     

周仕勇  王桂岭 《内陆地震》1990,(4)

研究新疆伊宁——乌鲁木齐和乌什——库尔勒1972年以来发生的49个震群的ρ值表明,ρ<0.55可作为前兆震群的判据指标。分析了ρ<0.55标准下的前兆震群的预测能力,认为,震群序列的ρ值具有一定的预报效能。  相似文献   

农桐间作地热量平衡和水分利用状况研究   总被引：5，自引：0，他引：5  

景元书  刘乃壮 《南京气象学院学报》1995,18(4):560-565

由实测资料系统分析了农桐间作地热量平衡各分量复杂的时空变化特征。结果表明：间作内外蒸发耗热（ＬＥ）仍是主要耗热项，湍流耗热（Ｈ）低于ＬＥ，但高于土壤热通量（Ｑ）；间作地各分量小于对照，但ＬＥ、Ｑ占净辐射（Ｒｎ）比值高于对照；泡桐林带对各分量的影响与间作结构及测点位置有关。然后计算了间作中小麦、棉花水分利用率（ＷＵＥ），其值与作物类型，生长期等因子有关，且间作地高于对照。  相似文献   

Performance Prediction of Circular Diamond Saws from Mechanical Rock Properties in Cutting Carbonate Rocks   总被引：2，自引：0，他引：2  

M. Fener  S. Kahraman  M. O. Ozder 《Rock Mechanics and Rock Engineering》2007,40(5):505-517

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中国高技术产业投入产出有效性地区差异分析   总被引：6，自引：0，他引：6  

张纯  葛幼松 《地理与地理信息科学》2007,23(3):59-63,77

运用DEA方法,从综合有效性、技术有效性和规模有效性3方面对全国30个省(市、区)(缺失西藏数据)的高技术产业投入产出有效性进行实证分析,根据技术有效性和规模有效性对其发展状态进行分类并提出相应对策。结果表明,我国高技术产业在现有的发展水平上存在投入产出效率不高、总体规模偏大等问题,各省市需针对自身特点制定相应发展策略。  相似文献   

On Continent-Continent Point-Collision and Ultrahigh-Pressure Metamorphism   总被引：4，自引：0，他引：4  

DONG Shuwen  Chinese Academy of Geological Sciences  Baiwanzhuang Ro  Beijing WU Hongling  LIU Xiaochun  XUE Huaimin Institute of Geomechanics  Chinese Academy of Geological Sciences  Beijing Fei Zhenbi 《《地质学报》英文版》2002,76(1):69-80

Up to now it is known that almost all ultrahigh-pressure (UHP) metamorphism of non-impact origin occurred in continent-continent collisional orogenic belt, as has been evidenced by many outcrops in the eastern hemisphere. UHP metamorphic rocks are represented by coesite- and diamond-bearing eclogites and eclogite facies metamorphic rocks formed at 650-800℃ and 2.6-3.5 GPa, and most of the protoliths of UHP rocks are volcanic-sedimentary sequences of continental crust. From these it may be deduced that deep subduction of continental crust may have occurred. However, UHP rocks are exposed on the surface or occur near the surface now, which implies that they have been exhumed from great depths. The mechanism of deep subduction of continental crust and subsequent exhumation has been a hot topic of the research on continental dynamics, but there are divergent views. The focus of the dispute is how deep continental crust is subducted so that UHP rocks can be formed and what mechanism causes it to be subducte  相似文献   

基于正交设计的复杂坝基弹塑性力学参数反演   总被引：8，自引：1，他引：8  

陈益峰  周创兵 《岩土力学》2002,23(4):450-454

复杂坝基弹塑性力学参数反演的计算工作量直接取决于采用何种优化方法。根据大坝在运行期的实测资料，运用有限元正交数值试验、回归分析和优化相结合的方法，反演了坝基岩体的弹塑性力学参数。实例研究表明了该方法的有效性和实用性。  相似文献