Multi-photon resonance enhanced super high-order harmonic generation

This paper proposes highly charged ions pumped by intense laser to produce very high order harmonics. Numerical simulations and full quantum theory of Ne⁹⁺ ions driven by laser pulses at 1064 nm in the power range of 10⁹ W/cm² ～ 10¹⁵ W/cm² show that the emission spectrum corresponds to the electronic transitions from the excited states to the ground state, which is very different from the spectrum of general high-order harmonic generation. In such situation, harmonic order as high as 1000 can be obtained without producing lower order harmonics and the energy conversion efficiency is close to general high order harmonic generation of hydrogen atom in the same laser field.     

Activities and tendency of mountain hazards induced by the MS7. 0 Lushan earthquake,April 20, 2013

滑坡是地震触发最常见和最严重的次生灾害,会造成巨大的财产损失,甚至是人员伤亡。因此,地震作用下,边坡的稳定性分析及加固措施的有效性成为工程地质领域重要研究课题之一。本文以巧家县白泥沟滑坡为例,依托二维有限差分程序FLAC,模拟滑坡在不同支护结构下的加固效果。该滑坡属于巨型厚层基岩滑坡,下滑力巨大,因此采用双排抗滑桩、锚索抗滑桩和锚索及连续桩键结构3种支护方式。结果表明：双排抗滑桩能分担坡体下滑力,但抗滑桩所承受的下滑力依旧较大,导致桩身顶端出现推动周围土体下滑的现象;锚索抗滑桩和锚索支护能提供较大的抗滑力,减小边坡的下滑趋势,锚索中施加预应力能有效抑制桩顶位移,提高桩身承载能力;连续桩键结构的内力分配合理,具有较好的整体性,这种整体性能明显提高抗滑能力。3种支护结构中,连续桩键结构对边坡加固效果最好。     

Effects of diesel oil on the polychaete Annelida in model benthic ecosystem

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2013年芦山MS7.0地震序列参数的早期 特征: 传染型余震序列模型计算结果

为考察2013年4月20日芦山M_S7.0地震震后序列参数的早期特征, 利用“传染型余震序列”(ETAS)模型和最大似然法进行了参数估计. 设定截止震级M_c=M_L2.0, 拟合时段为震后0.31—24.12天, 计算获得α=1.89, p=1.22, 同时利用最大似然法估计获得b=0.72. 与中国大陆地区其它中强震的余震序列参数的比较表明, 芦山M_S7.0地震序列参数表现为触发次级余震的能力较弱和序列衰减速率较快的特征, 反映出余震区相对较高的应力水平. 为检测结果的稳定性, 设定不同的截止震级M_c以及不同的拟合截止时间, 分别进行参数拟合和参数标准差估计. 结果表明, M_c的选取对α值影响明显, 对p值影响则较小. 此外, 震后10天内获得的参数拟合结果随时间变化较为明显, 而其后各参数变化总体较为平稳.      

Uncertainties in estimates of cropland area in China: a comparison between an AVHRR-derived dataset and a Landsat TM-derived dataset

The large uncertainties in estimates of cropland area in China may have significant implications for major cross-cutting themes of global environmental change—food production and trade, water resources, and the carbon and nitrogen cycles. Many earlier studies have indicated significant under-reporting of cropland area in China from official agricultural census statistics datasets. Space-borne remote sensing analyses provide an alternative and independent approach for estimating cropland area in China. In this study, we report estimates of cropland area from the National Land Cover Dataset (NLCD-96) at the 1:100,000 scale, which was generated by a multi-year National Land Cover Project in China through visual interpretation and digitization of Landsat TM images acquired mostly in 1995 and 1996. We compared the NLCD-96 dataset to another land cover dataset at 1-km spatial resolution (the IGBP DIScover dataset version 2.0), which was generated from monthly Advanced Very High Resolution Radiometer (AVHRR)-derived Normalized Difference Vegetation Index (NDVI) from April, 1992 to March, 1993. The data comparison highlighted the limitation and uncertainty of cropland area estimates from the DIScover dataset.     

不同甘蔗品种锤度与糖分的关系

使用大田实验数据和实验室数据建立了实验室锤度和田间锤度与甘蔗糖分关系的数学模型。统计分析表明 ,实验室锤度、田间锤度与糖分间均存在显著的线性关系 ,并且实验室锤度———糖分关系与大田锤度———糖分关系存在显著性 (α =0 .0 5 )差异 ;而不同甘蔗品种间的田间锤度———糖分关系无显著性差异 (α =0 .0 5 )。故不同的取样方法应使用不同的方程来估计甘蔗糖分 ;而不同甘蔗品种间田间锤度———糖分关系可用同一模型来描述。对三个供试甘蔗品种应用该模型进行实测验证 ,实测与预测值的相对误差均在 7%以内。     

Experimental investigation of the hydraulic properties of large-scale irregular fractured rock masses in granite fault zones

Hydrogeology Journal - Permeability is one of the critical parameters for evaluating the hydraulic properties of water-conducting media. Variations in the hydraulic properties generally lead to...     

基于广义高斯模型的机载测深LiDAR波形拟合算法

针对传统LiDAR测深波形拟合算法受噪声干扰严重、对微弱回波信号及复杂波形拟合不准确的问题,提出一种基于广义高斯模型的波形拟合算法。首先通过计算滤波前后尾段波形的差异估计波形的噪声;然后利用广义高斯模型提取海面与海底反射信号分量,并对剩余信号进行迭代拟合;最后利用LM算法对参数进行优化,并对优化后的参数进行约束,避免冗余分量。采用南海实测数据进行验证,该算法拟合微弱回波及复杂波形能力强,不论在浅水(回波发生叠加)还是深水,其拟合精度均优于传统算法,具有良好的鲁棒性。     

可达性视角下中心城市辐射场时空格局演变——以浙江省为例

综合交通网络演进产生的时空压缩效应对于中心城市辐射场时空格局演变具有重要影响。在Arc GIS10.0空间分析模块支持下,通过城市综合影响力指数和场强、场能模型对2005,2014年浙江省11个地市的辐射场时空格局演变进行测度研究,并对腹地划分、扩展趋势及偏移度进行分析。研究发现:(1)随着交通网络不断完善和综合实力不断提升,浙江省总体空间场能不断提高,但中心高于外围、干线高于周边以及北部高于南部等区域差异现象明显;(2)以杭州为枢纽的高铁网络成为场能集聚新高地,空间场能呈现以"X"型高铁线为骨架的新型分布格局;(3)杭州、宁波以及金华等地市具有较高腹地偏移度,其腹地超出自身市域并延伸袭夺周边相邻乃至非相邻地市腹地范围;(4)大部分地市腹地与政区范围吻合度较差,少数地市"小马拉大车"现象突出,腹地与政区匹配关系的研究可为浙江省重构城市经济功能区划和指导区域经济一体化发展提供重要参考。