土地整理为农村土地流转搭建基础平台——浙江省慈溪市土地流转调查与思考

促进土地承包经营权流转,发展多种形式的适度规模经营,是提高耕地质量,保护优质、集中、连片耕地,增加土地收益的重要路径之一。本文通过分析土地流转第一大县浙江省慈溪市农村土地流转的动因、做法和经验,阐述了市场环境和政府服务在土地流转中的推动作用。文章认为,政府投资土地整理项目是田水路林村的综合治理,促进了慈溪市农村土地流转和规模经营,既保生产,又关注了生活和生态,受到基层政府和农民欢迎。文章提出了土地整理在农村土地流转中的基础平台作用,并对完善与土地流转相关的土地管理制度提出了相关建议。     

页岩储层体积压裂复杂裂缝支撑剂的运移与展布规律

为了研究页岩储层体积压裂复杂裂缝支撑剂的运移与展布规律,构建了大尺度复杂裂缝支撑剂运移与展布评价实验系统,测试了次裂缝角度、注入排量、加砂浓度、支撑剂粒径、压裂液黏度等对支撑剂运移与展布的影响,研究了主/次裂缝中支撑剂的运移与展布规律。结果表明:(1)裂缝中流体流态随裂缝支撑高度增加逐步由层流向紊流转变;(2)支撑剂在裂缝中的运移方式主要包括悬浮运移和滑移运动;(3)分支前主裂缝的支撑剂展布形态与次裂缝角度、注入排量、加砂浓度和支撑剂粒径等参数相关,其中注入排量为最主要的影响因素;(4)分支后主裂缝的支撑剂质量比与次裂缝角度、注入排量、液体黏度、加砂浓度和支撑剂粒径呈正比,同次裂缝与主裂缝的流量比呈反比;(5)分支后次裂缝的支撑剂质量比与注入排量、次裂缝与主裂缝的流量比、压裂液黏度呈正比,与次裂缝角度、加砂浓度和支撑剂粒径呈反比;(6)分支后主裂缝的砂堤前缘角度同加砂浓度、支撑剂粒径、次裂缝与主裂缝的流量比呈正比,与次裂缝角度、注入排量和压裂液黏度呈反比;(7)次裂缝的砂堤前缘角度同次裂缝角度、加砂浓度与支撑剂粒径呈正比,和注入排量、压裂液黏度、次裂缝与主裂缝的流量比呈反比。结论认为,该研究成果可以为页岩储层体积压裂支撑剂的优选和压裂方案设计提供理论支撑。     

我国农业非点源污染现状研究

我国农村的非点源污染已经开始对生态环境产生巨大影响,尤其对地表水和土壤的影响更为严重.该文首先概述了农业非点源污染的特点、现状及危害等;其次表明了农业非点源污染主要来自农用化肥、农药的使用和畜禽废水、废物的排放;最后提出了控制非点源污染的相关对策.     

含软弱夹层岩质边坡在爆破地震波下的试验研究

为探求地质工程中爆破地震波作用下含软弱夹层边坡的动力响应特性,设计由混凝土基座和边坡模型组成的物理模拟试验,采用雷管和乳化炸药施加爆破地震波,开展考虑爆破孔位置和炸药量影响的多次爆破试验.首先,对速度、加速度响应分别进行快速傅里叶变换(FFT)、希尔伯特—黄变换(HHT),两者的频谱结果均表明符合爆破地震波的特征;然后...     

Automated optimum design of wing structures: A probabilistic approach

The optimization of aircraft wing structures is presented by considering the dynamic stresses developed during landing impact and gust load conditions. The random nature of the sinking speed and the forward velocity at the instant of contact is considered in the calculation of landing stresses. The vertical velocity due to gust is treated as a stochastic process for the computation of gust-induced stresses. The optimum designs of a symmetric double wedge airfoil, based on beam type of analysis, and a supersonic airplane wing, based on finite element analysis, are considered to illustrate the procedure. A graphical procedure is used in the case of the double wedge airfoil, and nonlinear programming techniques are used in the case of the supersonic wing, for finding the optimum solutions.     

基于遥感技术的打狗河流域1999-2009年间石漠化及绿化研究

采用遥感技术对打狗河流域1999-2009年期间的植被覆盖及变化进行提取,完成了区域内耕地、石漠、火烧迹地、荒草地、灌草、灌丛、密灌及林地等7种类型土地的相互转化分析。重新定义了石漠化及绿化,并根据植被退化程度将全区石漠化分为轻度、中度和重度;将全区植被恢复程度分为轻度、中度和深度。基于遥感技术提取的7种地物类型数据的分析,全区石漠化有轻度加剧的迹象,石漠化比例略高于绿化比例。10年间石漠化和绿化相互转化的面积基本相当,分别占全区面积的30.83％和30.55％;其中中度和轻度石漠化面积分别约占8.60％和30.83％,均略大于中度和轻度绿化的6.85％和30.55％。     

Stochastic modeling and performance analysis in balancing load and traffic for vehicular ad hoc networks: A review

The rapid growth of vehicular applications has resulted in high demand for Internet technology, which demands an unprecedented network capacity and a high quality of service (QoS). In vehicular ad hoc networks (VANETs), since nodes (vehicles) are highly mobile. The dynamic nature of the network topology in the VANET system changes due to frequent changes in link connectivity. The vehicles-to-vehicles (V2V), vehicles-to-infrastructure (V2I), and QoS, as well as the heterogeneity of applications within the VANET. VANETs have been introduced to make driving comfortable by providing safety and support to drivers. Due to the flexibility and offloading schemes available in-vehicle applications, there are some limitations. However, there are many issues in providing optimum service provisioning and scheduling in the vehicular environment. In VANETs, BSs and roadside units (RSUs) improve QoS. However, Internet services transmit packets to vehicles using stochastic models, and it predicts the traffic on a VANET. We provide open challenges to drive stochastic models in this direction.     

Verification of robust diagnosability for partially observed discrete event systems

In this paper, we study robust failure diagnosis of discrete event systems. Given a set of possible models, each of which has its own nonfailure specification, we consider the existence of a single diagnoser such that, for all possible models, it detects any occurrence of a failure within a uniformly bounded number of steps. We call such a diagnoser a robust diagnoser. We introduce a notion of robust diagnosability, and prove that it serves as a necessary and sufficient condition for the existence of a robust diagnoser. We then present an algorithm for verifying the robust diagnosability condition.     

Sm doping effect on structural,morphological, luminescence and antibacterial activity of CdO nanoparticles

Undoped cadmium oxide along with samarium doped CdO are synthesized by simple soft precipitation method. Resulting precursor was calcined at 400 °C for 2 h. As a result of heating, a pure material was produced. The obtained compound possesses a cubic crystalline structure at nanoscale. Also, FESEM image showed that the resulting material is composed of nanoparticles and its size decreases with increase of Sm doping relative with the particle size calculated from XRD. The photoluminescence shows the emission of violet and blue colour peaks and the peak at 468 nm which is responsible for a better antibacterial activity. The synthesized nanopowders are subjected to two different gram positive (Staphylococcus aureus and Enterococcus faecalis) and two different gram negative (Escherichia coli and Klebsiella pneumoniae) bacterial strains respectively. It is noted that there are high activity of the Sm doped CdO towards gram negative bacteria.     

Application of SWAT99.2 to sensitivity analysis of water balance components in unique plots in a hilly region

Although many sensitivity analyses using the soil and water assessment tool (SWAT) in a complex watershed have been conducted, little attention has been paid to the application potential of the model in unique plots. In addition, sensitivity analysis of percolation and evapotranspiration with SWAT has seldom been undertaken. In this study, SWAT99.2 was calibrated to simulate water balance components for unique plots in Southern China from 2000 to 2001, which included surface runoff, percolation, and evapotranspiration. Twenty-one parameters classified into four categories, including meteorological conditions, topographical characteristics, soil properties, and vegetation attributes, were used for sensitivity analysis through one-at-a-time (OAT) sampling to identify the factor that contributed most to the variance in water balance components. The results were shown to be different for different plots, with parameter sensitivity indices and ranks varying for different water balance components. Water balance components in the broad-leaved forest and natural grass plots were most sensitive to meteorological conditions, less sensitive to vegetation attributes and soil properties, and least sensitive to topographical characteristics. Compared to those in the natural grass plot, water balance components in the broad-leaved forest plot demonstrated higher sensitivity to the maximum stomatal conductance (GSI) and maximum leaf area index (BLAI).