基于支持向量机与余弦夹角法的中文网页过滤的研究与设计

为了进一步准确过滤对青少年危害较大的色情网页,在汉语词法分析系统添加去禁用词功能实现中文分词,通过改进的词频-逆文档频率及文档频率-互信息方法完成特征提取,从而实现基于支持向量机的过滤方案。并在给出的余弦夹角公式的基础上,提出了一种基于余弦夹角法的中文网页过滤方案。结合两种方案,实验证明在统一资源符总库存在条件下方案对色情等网页过滤效果进一步提高。     

The Optimized Short-Range Ensemble Forecast Based on Singular Vector Calculations

In ensemble forecast,by summing up ensemble members,filtering the uncertainty,and retaining the common component,the ensemble mean with a better result can be achieved.However,the filtering works only when the initial perturbation develops nonlinearly.If the initial perturbation propagates in a linear space,the positive and negative members will counteract,leading to little difference between ensemble mean and control forecast and finally insignificant ensemble result.In 1 2-day ensemble forecast,based on singular vector (SV) calculations,to avoid this insignificance,the counteracting members originated from the same SV are advised not to put into the ensemble system together;the only candidate should be the one with the better forecast.Based on the ingredient analysis of initial perturbation development,a method to select ensemble members is presented in this paper,which can fulfill the above requirement.The regional model MM5V1 of NCAR/PSU (National Center for Atmosphere Research/Pennsylvania State University) and its corresponding tangent adjoint model are used.The ensemble spread and forecast errors are calculated with dry energy norm.Two mesoscale lows on the Meiyu front along the Yangtze River are examined.According to the analysis of the perturbation ingredient,among couples of counteracting members from different SVs,those members performing better always have smaller or greater spread compared with other members.Following this thinking,an optimized ensemble and an inferior ensemble are identified.The ensemble mean of the optimized ensemble is more accurate than that of the inferior ensemble,and the former also performs better than the traditional ensemble with positive and negative members simultaneously.As for growth of the initial perturbation,those initial perturbations originated from the summed SVs grow more quickly than those from the single SV,and they enlarge the range of spread of the ensemble effectively,thus leading to better performance of ensemble members.     

东亚冬季1 000 hPa环流异常与我国气候的关系

将NCEP／NCAR 1951／1952～2003／2004年东亚冬季1000hPa风场进行向量EOF分解,研究其第一特征模态的时空变化及其与我国气候异常的关系。结果表明,EOF1时间系数能够很好地刻画东亚冬季风的强度变化。强（弱）EOF1时间系数时,冬季我国气候冷、干（暖、湿）,次年春季东北及河套等地区的温度明显偏低（高）;次年夏季长江中下游地区的降水明显偏少（多）,华北和华南降水则偏多（少）,长江流域和江南地区的温度偏高（低）,华南及西南地区夏季则温度偏低（高）。     

基于支持向量机的多维地震时间序列建模

文中首先介绍了支持向量机回归方法,然后对其进行了数值仿真实验,最后利用该方法对首都圈地区的地震活动进行回归建模与内符检验。分析认为,利用该方法可以获得较强的多维地震样本学习、建模与外推泛化能力,具有较高的中长期地震危险性估计能力。     

基于光流矢量行波分离的相关加权逆时偏移成像

逆时偏移由于基于双程波方程进行波场延拓, 应用互相关成像条件所得到的成像结果中包含了大量的低波数噪声.基于Poynting矢量行波分离的逆时偏移方法虽可有效压制这些噪声干扰, 但其也存在Poynting矢量计算不稳定、行波分离精度不高以及各行波分离成像剖面叠加权重难以确定等问题.本文基于光流矢量实现了震源正时波场和检波点逆时波场的高精度分离, 分别得到了左上、左下、右上、右下四个方向的行波, 进而由正时和逆时波场的每两个行波互相关得到16个成像剖面; 在此基础上, 将这16个成像剖面分别与参考剖面做相关计算, 并将相关值作为权重分别赋予各成像剖面, 最终实现了基于光流矢量行波分离的相关加权逆时偏移成像.理论模型数据与实际资料试算表明: 相比于常规基于Poynting矢量行波分离的逆时偏移方法, 本文方法可更精确、稳定地实现震源波场和检波点波场的行波分离, 同时该方法采取的相关加权成像方式, 避免了人为取舍或仅赋予各波场成像剖面经验权重的缺陷, 有效提高了逆时偏移的成像精度.

     

Experimental Study of Dissolution Rates of Fluorite in HCl–H2O Solutions

The experiments of the dissolution kinetics of fluorite were performed in aqueous HCl solutions over the temperature range of 25–100 °C using a flow-through experimental apparatus. With a constant input of aqueous HCl solution through the reactor, output concentrations of the dissolved species Ca, F, Cl vary with flow rate, as well as with the surface compositions. Measured output concentrations of dissolved species and the pH can be used to determine a rate law for fluorite dissolution. Fluorite dissolution rates are found to be pH dependent. Usually, dissolution rates of fluorite decreases with increasing dissolved Ca in the output solution at 25 and 100 °C. Dissolution rate can be expressed as

Long and short term relationships between solar wind velocity and geomagnetic field at low latitudes

Solar wind velocity control of low latitude geomagnetic field both on long and short term basis is studied. It is shown that semiannual averages of the low latitude field is inversely related to solar wind velocity and that there is a dominant local time dependence of the relationship. Strongest correlation are confined to the local afternoon hours. It is also shown that for a duration when the solar wind velocity exhibits significant recurrent pattern the low latitude geomagnetic field also depicts strong solar synodic rotation periodicity of 27 days with significant coherence with velocity. The low latitude field on a short term basis is influenced by variable solar wind velocity with a delay of about 1–2 days. During the period of systematic recurrent pattern in solar wind velocity even the quiet-time night field at equatorial and low latitudes show a strong dependence on velocity indicative of the solar wind control of the quiet-time proton belt encompassing the earth.     

水下目标方位估计的一种新方法

矢量传感器是一种新型水声传感器。介绍了应用矢量传感器确定目标方位的理论和方法，给出了仿真和实验研究结果，讨论了矢量传感器具体体积小、输出信号多、抗各向同性干扰等特性。最后定性地分析了目标方位的方位估值误差。     

新疆阿克苏河上游高寒草甸蒸散发观测与估算

蒸散发是水循环的关键环节, 是水量平衡的重要组成部分. 由于在高寒山区进行长期野外观测的难度较大, 导致对区域实际蒸散发的认识不清, 从而无法明确区域水资源分配与不同植被的生态水文功能. 在天山山区, 高寒草甸占其总面积近15%, 其对降水的调节作用巨大, 但目前高寒草甸的实际蒸散发量多用潜在蒸散发进行推算, 缺少实际观测数据. 2012年10月-2013年9月, 利用3个小型蒸渗仪观测了阿克苏河上游科其喀尔冰川综合考察站附近山区的高寒草甸的实际蒸散量, 并尝试利用最小二乘支持向量机(LS-SVM)估算实际蒸散发. 结果表明:研究区高寒草甸全年内实测蒸散量511.3 mm, 日均蒸散量为1.4 mm·d^-1; 在不同时期, 蒸散量变化剧烈, 冻结期、生长前期、生长期和生长后期的蒸散量分别为53.9、41.0、363.8和52.6 mm, 分别占全年蒸散量的10.5%、8.0%、71.2%和10.3%. 最小二乘支持向量机对实际蒸散发的估算精度较高, 对观测资料相对缺乏的高寒山区来说, 不失为一种较好的估算蒸散发方法.     

超站仪HD-STGPS的基线向量解算

介绍了HD－STGPS中基线向量解算软件的设计思想和实现特色。对流动站、定向点的GPS观测、用全站仪发展支站以及检核测量等应用了必要的说明。