Automatic user goals identification based on anchor text and click-through data

Understanding the underlying goal behind a user＇s Web query has been proved to be helpful to improve the quality of search. This paper focuses on the problem of automatic identification of query types according to the goals. Four novel entropy-based features extracted from anchor data and click-through data are proposed, and a support vector machines （SVM） classifier is used to identify the user＇s goal based on these features. Experi- mental results show that the proposed entropy-based features are more effective than those reported in previous work. By combin- ing multiple features the goals for more than 97% of the queries studied can be correctly identified. Besides these, this paper reaches the following important conclusions： First, anchor-based features are more effective than click-through-based features; Second, the number of sites is more reliable than the number of links; Third, click-distribution- based features are more effective than session-based ones.     

一种实用的混合有源电力滤波器的设计和仿真

提出了一种结构简单,实用性比较强的拓扑结构,分析了混合有源滤波器(HAPF)各部分器件参数选取的方法,并介绍开关管关断尖峰电压的抑制措施;实验仿真结果表明,这种混合有源滤波器较好地发挥了无源滤波器(PF)和有源滤波器(APF)的优点,并减小了系统的容量,具有良好的无功电流和谐波电流补偿效果.     

川滇地区地壳结构的虚拟地表震源 反射测深法研究

基于中国地震局地质研究所在中国四川西部布设的流动地震观测台阵数据,用近年发展起来的虚拟地表震源反射测深方法研究川滇地区的地壳结构。结果表明,川滇地块、松潘-甘孜地块和杨子地块3个地块虚拟地表震源反射测深的莫霍面深度存在明显差异:1)四川盆地为40 km左右;2)川滇地块为45~50 km;3)松潘-甘孜地块为30~40 km。四川盆地虚拟地表震源反射测深的莫霍面深度与艾里重力均衡模型所预测的结果基本上一致,而川滇地块和松潘-甘孜地块虚拟地表震源反射测深的莫霍面深度明显小于前人得到的接收函数莫霍面深度和艾里重力均衡模型预测的结果。可能与四川盆地地壳结构简单,而川滇地块及松潘-甘孜地块地壳结构复杂有关。同时,结果显示,在鲜水河断裂和安宁河断裂处虚拟地表震源反射测深的莫霍面深度明显变浅,可能与这些深大断裂处地幔物质的上涌有关。研究结果可为认识青藏高原东南缘的构造变形模式提供新的约束。     

基于遥感协同数据对岩性进行监督分类——以阿尔金西段江格勒萨依地区为例

阿尔金西段高压变质带是地质科学研究热门地区,而江格勒萨依地区又是深入探索该地区的重要前沿基地之一,考虑到该区自然地理环境,无法实地进行细致调查,因此遥感地质调查成为重要手段。收集光谱分辨率居中的Landsat-8数据和空间分辨率相对较高的Worldview-2数据,并以Landsat-8数据光谱特征和Worldview-2数据纹理特征为主辅以Worldview-2数据光谱特征进行协同得到协同数据,通过对原始数据和协同数据进行最大似然法监督分类,得到该地区中生代沉积岩及前寒武变质岩分类结果,验证表明协同数据分类总体精度较高,监督分类方法在阿尔金西段地质调查过程中具有推广的可能性。     

Dominant bacteria correlated with elimination of sludge in an innovative reactor

This study was conducted to identify bacteria responsible for the elimination of sludge in an innovative gravel contact oxidation reactor (GCOR) and a conventional activated sludge reactor (ASR),Fluorescent in situ hybridization revealed that α-,β-,γ-and ε-Proteobacteria and Bacteroidetes were present in both reactors.In the GCOR,γ-Proteobacteria accounted for 13% of the biofilm biomass on the carrier,while α-,ε-and β-Proteobacteria accounted for 12%.However,the predominant bacteria in the pores of the carrier in the GCOR were Bacteroidetes (18%),ε-Proteobacteria (13%),β-and α-Proteobacteria (10%) and γ-Proteobacteria (9%).Conversely,β-Proteobacteria (18%),Bacteroidetes (13%),α-and γ-Proteobacteria (12%) and ε-Proteobacteria (5%) dominated the sediment community of the ASR.     

Predictive control for mechanical system with backlash based on hybrid model

The mechanical system with backlash is distinguished between a “backlash mode” and a “contact mode”. The inherent switching between the two operating modes makes the system a prime example of hybrid system. For eliminating the bad effect of backlash, a piecewise affine (PWA) model of the mechanical servo system with backlash is built. The optimal control of constrained PWA system is obtained by taking advantage of model predictive control (MPC) method, and the explicit solution of MPC in a look-up table form is figured out by combining the dynamic programming and multi-parametric quadratic programming, thereby establishing an explicit hybrid model predictive controller. Furthermore, a piecewise quadratic (PWQ) function for guaranteeing the stability of closed-loop control is found by formulating the search of PWQ function as a semi-definite programming problem. In the tracking experiments, it is demonstrated that the explicit hybrid model predictive controller has a good traction control effect on the mechanical system with backlash. The error meets the demands of real system. Further, compared to the direct on-line computation, the computation burden is reduced by the explicit solution, thereby being suitable for real-time control of system with short sampling time.     

P110油管用钢液固两相流体冲蚀实验研究

在油气井压裂改造过程中,高速含砂流体引起的冲蚀是油管失效的重要原因之一。利用自制的喷射式冲蚀实验装置,以3.5wt%NaCl含砂流体为介质,研究了油井管常用的P110油管用钢冲蚀速率随冲蚀时间、介质流速和含砂量的影响。研究结果表明,在冲蚀时间60~90 min时,P110钢材的冲蚀速率趋于稳定;在传统的纯冲刷磨损公式E=KVn基础上,增加了腐蚀因子M对公式进行修正,与实验数据尤其是低流速时的实验数据拟合误差减小;砂含量在25 kg/m3时,冲蚀速率达到最大;继续增加含砂量时,颗粒之间碰撞消耗的动能使得冲蚀速率先减小,然后缓慢增加。实验结果为P110油管在新型储层改造中的应用提供了一定参考。     

基于DPGrid的高分辨率航空影像快速纠正与更新

DPGrid(数字摄影测量网格系统)是将计算机网络技术、并行处理技术、高性能计算技术与数字摄影测量处理技术相结合而研制的新一代摄影测量处理平台,其性能远远高于当前的数字摄影测量工作站。DPGrid高性能遥感影像自动处理模块包括自动空三DPGrid.AT、光束法平差DPGrid.BA和正射影像全自动并行处理系统DPGrid.OP。本文以高分辨率航空影像为基础,采用DPGrid软件,基于已有的正射影像数据及数字高程模型,实现影像的快速纠正与更新。     

W频段波导功率分配器的设计

波导功率分配器是微波、毫米波系统中常用的重要部件,但是传统匹配结构因加工困难而在W频段很难实现.文中首先利用基于亥姆霍兹方程弱形式的有限元法设计了一种圆弧匹配结构,该结构的半径为铣床刀头的半径,故其轮廓与铣床刀头的外边缘匹配,可以方便地在普通铣床上加工,有效地降低制作成本;然后采用两对圆弧和三对圆弧的匹配结构分别设计了H面和E面波导功率分配器.该功率分配器散射参数的计算结果与实验结果吻合得很好,表明文中的设计方法具有很好的工程应用价值.     

基于FM广播的无源雷达自适应回波重建系统研究

介绍了采用调频广播作为外辐射源的无源雷达,因FM广播载频高和带宽窄,采用窄带采样定理可以保证在信号无失真采样的前提下大大降低采样频率,为实时信号处理提供方便。另外,目标回波会受到较强的直达波干扰影响,由于多普勒频移相对较小,目标回波与直达波干扰频谱混叠严重,使用经典滤波器进行直达波干扰抑制十分困难。因此,设计了基于最小均方的自适应回波重建系统,仿真表明,直达波干扰抑制效果明显,目标回波得到较好重建,自适应回波重建系统工作性能良好。