顾及字符特征的中文地名词典查询方法     

叶鹏  张雪英  杜咪 《地球信息科学学报》2018,20(7):880-886

地名词典查询是地名校正、地名匹配等地名服务应用的重要基础,但是地名数量的快速增长使得词典查询性能面临严峻挑战。针对大规模数据环境中传统词典查询方法准确率不高且效率较低等问题,提出了一种顾及字符特征的中文地名词典查询方法（CGQM）。首先,查询具有相同字符特征的地名形成候选地名集合,同时构建单字索引提升查询效率;其次,依据字符数量特征比较查询地名与候选地名的差异,进一步过滤候选地名集合;最后,基于字符位置特征优化查询结果排序策略,使得结果排序更为合理。实验以全国地名词典为例,构建5组测试集进行CGQM方法与Lucene检索方法的对比分析。研究结果表明,CGQM方法对于增强地名词典查询功能、提升查询效率具有实际意义。  相似文献   

The effect of expansion ratio on the critical Reynolds number in single fracture flow with sudden expansion          下载免费PDF全文

Jiazhong Qian  Lei Ma  Hongbin Zhan  Qiankun Luo  Xiao Wang  Mu Wang 《水文研究》2016,30(11):1718-1726

Flow in a single fracture (SF) is an important research subject in groundwater hydrology, hydraulic engineering, radioactive nuclear waste repository and geotechnical engineering. An abruptly changing aperture is a unique type of SF. This study discusses the relation between the values of the critical Reynolds number (Re_c) for the onset of symmetry breaking of flow and the expansion ratio (E) of SF, which is defined as the ratio between the outlet (D) and inlet (d) apertures. This study also investigates the effect of inlet aperture d on Re_c for flow in an SF with abruptly changing apertures (SF‐ACA) using the finite volume method. Earlier numerical and experimental results showed that flow is symmetric in respect to the central plane of the SF‐ACA at small Reynolds number (Re) but becomes asymmetric when Re is sufficiently large. Our simulations show that the value of Re_c decreases with the increasing E, and the relationship between the logarithm of Re_c and E can be described accurately using either a quadratic polynomial function or a logarithmic function. However, the relationship of Re_c and d for a given E value is vague, and Re_c becomes even less sensitive to d when E increases. This study also reveals that the hydraulic gradient (J) and flow velocity (v) follow a super‐linear relationship that can be fitted almost perfectly by the Forchheimer equation. The inertial component (J_i) of J increases monotonically with Re, whereas the viscous component (J_v) of J decreases monotonically with Re. The Re value corresponding to equal inertial and viscous components of J (named as the transitional point Re) decreases when E increases, and such a transitional point Re should be closely related to the critical Reynolds number Re_c, although a rigorous theoretical proof is not yet available. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

A late Quaternary vertebrate deposit in Kudjal Yolgah Cave,south‐western Australia: refining regional late Pleistocene extinctions          下载免费PDF全文

Nathan R. Jankowski  Grant A. Gully  Zenobia Jacobs  Richard G. Roberts  Gavin J. Prideaux 《第四纪科学杂志》2016,31(5):538-550

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Brillouin scattering study on elastic and piezoelectric properties of laser irradiated ZnO single crystals     

刘洁  蒋毅坚 《海洋学报(英文版)》2010,29(11)

Brillouin light scattering technique can be successfully used to determine the whole set of elastic and piezoelectric constants of a ZnO single crystal irradiated by different laser energy densities, into a micron range (radiation layer thickness). It is found that the scattering intensity, the linewidth and the Brillouin scattering shift of acoustic phonons are all strongly dependent on laser energy density. Based on the sound propagation equations and these results, the directional dependences of the compressional and shear moduli of the irradiated ZnO sample in the (001) plane are investigated. It is found that under an appropriate laser condition, 248 nm KrF excimer laser irradiation can significantly improve the surface quality and increase the elastic properties of ZnO single crystal. This procedure has potential applications in the fabrication of ZnO-based surface acoustic wave and optic-electronic devices.  相似文献   

Borehole failure analysis in a sandstone under anisotropic stresses     

Euripides Papamichos 《国际地质力学数值与分析法杂志》2010,34(6):581-603

Borehole failure under anisotropic stresses in a sandstone is analyze numerically for various borehole sizes using a nonlinear elastic–plastic constitutive model for a Cosserat continuum. Borehole failure is identified as macroscopic failure of the borehole through the development of shear bands and breakouts. The results compare well both qualitatively and quantitatively with experimental results from polyaxial tests on Red Wildmoor sandstone. They show that the hole size effect of the borehole failure strength is independent of the far‐field stress anisotropy and follows a ? power law of the hole size. A similar scale effect equation with a ? power law is proposed for the scale effect of the maximum plastic shear strain at failure. This equation can be useful for better predicting hole‐size‐dependent failure with standard codes based on classical continua. The effect of stress anisotropy on the borehole failure stress is found to be independent of the hole size. The failure stress decreases linearly to 40% as the stress anisotropy increases. However, the maximum plastic shear strain at failure is stress anisotropy independent and therefore the critical plastic shear strain for failure is only hole‐size dependent. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

单片卫星影像在航测测图中的利用     

赵焕兰 《测绘与空间地理信息》2016,(9):153-155

在边境测图过程中,经常遇到较大面积云层问题,使航测测图无法顺利进行。能充分利用的影像资源是第一次全国地理国情普查的影像,有国产高分2号、SPOT-6、资源3号等单片卫星影像,无立体像对影像。通过对国情普查的影像分析选取,选取一试验区域进行试验,用国产高分2号卫星影像与SPOT-6卫星影像组成立体像对测制地物地貌,用Worldview卫星立体像对影像测制同一区域的地物地貌,将两种影像源组成立体模型测制的地物地貌进行比较及精度统计,说明单片卫星影像在航测测图中达到的精度。  相似文献   

GPS精密卫星钟差估计研究     

孟范伟 《测绘与空间地理信息》2016,(9):77-79

随着精密单点定位技术的发展,对于精确的卫星坐标以及卫星钟差改正精度的要求越来越高,精密卫星星历以及精密卫星钟差的求解成为制约精密单点定位技术发展的瓶颈。本文基于修复周跳的载波相位观测值与相位平滑伪距观测值,采用无电离层延迟星间单差精密卫星钟差估计模型,在先估计出整周模糊度后,进行了精密卫星钟差的估计,并采用与IGS事后精密钟差作二次差的方法进行精度分析,这对于提高精密单点定位精度具有一定的意义。  相似文献   

松辽盆地大陆科钻二开段大井眼钻井液技术     

郑文龙 《地质与勘探》2016,52(5):931-936

CCSD-SK2井是一口钻穿松辽盆地白垩纪陆相沉积地层的中国大陆科学钻探井。二开段先以216mm口径钻至2806.20m,然后进行444.5mm口径扩孔。泥页岩地层大井眼钻进过程中粘土矿物含量高且易造浆,砂砾岩层渗透性强易粘卡,井壁稳定控制与钻屑携带难度大。选用了钾铵聚合物钻井液体系和聚磺钻井液体系,通过正交实验确定了钻井液配方。将钻井液控制在合适的密度、较低的失水量以及较强的封堵性,有效实现了井壁稳定;保持适当的环空返速、较高的动塑比以及定期打稠塞举砂等措施,有效实现了井眼净化。1086.45m~1147.56m与1182.74m~1256.01m井段累计收获岩心130.90m,取心率达到97.41%,平均机械钻速为0.84m/h;最终顺利钻至2806.20m。  相似文献   

长距离单历元单频非差北斗网络差分方法     

祝会忠  李博  徐爱功  高猛 《测绘科学》2016,41(5):14-20

针对北斗卫星导航系统现有的网络差分方法多是基于GPS系统并采用双差定位模型,而双差定位模型的采用使得网络差分方法存在一些缺陷的问题,该文提出一种长距离单历元单频非差北斗网络差分方法;首先长距离北斗基准站网向覆盖区域内的北斗用户提供非差误差改正数;然后用户内插计算出自己所需的非差误差改正数,并改正北斗单频伪距观测值的误差;最后进行单历元单频网络差分定位。实验表明,该方法能够使用单历元单频伪距观测数据实现长距离北斗网络差分定位。  相似文献   

降水井改造为原位生产井的工艺设计及应用     

吕士东  孙友宏  李强  郭威  周科  王思远 《世界地质》2016,35(4):1185-1194

为有效地扩大油页岩原位开采区域和节约油页岩原位开采的成本,需将废置的降水井改造成为原位生产井。根据降水井与原位生产井井身结构的相似性,对农安油页岩原位开采先导试验工程基地的降水井改造工艺进行了设计和优化。同时研发了偏心轮式套管割管装置及三爪式套管打捞装置用于拔管施工。工程实践证明,该工艺具有步骤简单、合理、高效以及价格低廉等特点。偏心轮式套管割管装置及三爪式套管打捞装置应用在降水井改造中,均取得理想的效果。  相似文献