Authorization administration in a distributed multi-application environment

To meet the authorization administration requirements in a distributed computer network environment, this paper extends the role-based access control model with multiple application dimensions and establishes a new access control model ED-RBAC(Extended Role Based Access Control Model) for the distributed environment. We propose an extendable hierarchical authorization assignment framework and design effective role-registering, role-applying and role-assigning protocol with symmetric and asymmetric cryptographic systems. The model can be used to simplify authorization administration in a distributed environment with multiple applications.     

地应变震兆异常信息提取方法研究

分析了怀来台体积应变观测资料的特点,研究了体积应变观测资料的气压干扰、仪器漂移的剔除方法和预处理后的资料分析方法,在分析中发现,振幅因子和非潮汐应变速率在1996年以来,在首都圈地区中西部发生的中强地震前,均有大小不同、持续时间不等的异常,这些参数可作为怀来地震台今后地震分析和地震中短期预测的指标。     

气候变化和人类活动对永定河流域径流变化影响定量研究

以永定河流域为研究对象,在对永定河流域1957-2010年降水、实际蒸发和气温实测资料进行趋势分析的基础上,建立SWAT模型,验证了还原径流的必要性,对气候变化和人类活动对永定河流域径流的影响进行了定量研究。结果表明：20世纪60、70年代为永定河流域的丰水期,80年代至今为枯水期。永定河流域80年代后的实测径流资料受气候变化和人类活动影响显著,需进行径流还原后才能保证径流资料的一致性。气候变化是80年代后期径流减少的主要原因,其贡献量约占总减少量的65.4%,人类活动的贡献量占34.6%,也是不容忽视的因素。     

扩频微波网桥在新疆测震网络中的应用

以频率为2.4 GHz和5.8 GHz设备为例,对扩频微波网桥在新疆测震网络中的应用范围进行阐述;根据实际工作中无线网桥的安装架设经验,对在不同条件、不同环境下可能出现的问题提出相应解决方案.     

Prediction methods of spudcan penetration for jack-up units

Jack-up units are extensively playing a successful role in drilling engineering around the world, and their safety and efficiency take more and more attraction in both research and engineering practice. An accurate prediction of the spudcan penetration depth is quite instrumental in deciding on whether a jack-up unit is feasible to operate at the site. The prediction of a too large penetration depth may lead to the hesitation or even rejection of a site due to potential difficulties in the subsequent extraction process; the same is true of a too small depth prediction due to the problem of possible instability during operation. However, a deviation between predictive results and final field data usually exists, especially when a strong-over-soft soil is included in the strata. The ultimate decision sometimes to a great extent depends on the practical experience, not the predictive results given by the guideline. It is somewhat risky, but no choice. Therefore, a feasible predictive method for the spudcan penetration depth, especially in strata with strong-over-soft soil profile, is urgently needed by the jack-up industry. In view of this, a comprehensive investigation on methods of predicting spudcan penetration is executed. For types of different soil profiles, predictive methods for spudcan penetration depth are proposed, and the corresponding experiment is also conducted to validate these methods. In addition, to further verify the feasibility of the proposed methods, a practical engineering case encountered in the South China Sea is also presented, and the corresponding numerical and experimental results are also presented and discussed.     

Wave diffraction on arc-shaped floating perforated breakwaters

An analytical method is developed to study the sheltering effects on arc-shaped floating perforated breakwaters. In the process of analysis, the floating breakwater is assumed to be rigid, thin, vertical, and immovable and located in water with constant depth. The fluid domain is divided into two regions by imaginary interface. The velocity potential in each region is expanded by eigenfunction in the context of linear theory. By satisfying continuity of pressure and normal velocity across the imaginary fluid interface, a set of linear algebraic equations can be obtained to determine the unknown coefficients for eigenfunction expansions. The accuracy of the present model was verified by a comparison with existing results for the case of arc-shaped floating breakwater. Numerical results, in the form of contour maps of the non-dimensional wave amplitude around the breakwater and diffracted wave amplitude at typical sections, are presented for a range of wave and breakwater parameters. Results show that the sheltering effects on the arc-shaped floating perforated breakwater are closely related to the incident wavelength, the draft and the porosity of the breakwater.     

A novel model to assess soil productivity in the dry-hot valleys of China

Accurate evaluation of soil productivity has been a long-standing challenge. Although numerous models for productivity assessment exist, most are cumbersome to use and require substantial parameter inputs. We developed a new empirical soil productivity model based on field investigations of soil erosion, soil physicochemical properties, and crop yields in the dry-hot valleys (DHVs) in China. We found that soil pH, and organic matter and available potassium contents significantly affected crop yields under eroded conditions of the DHVs. Moreover, available potassium content was the key factor affecting soil productivity. We then modified an existing soil productivity model by adding the following parameters: contents of effective water, potassium, organic matter, and clay, soil pH, and root weighting factor. The modified soil productivity model explained 63.5% of the crop yield. We concluded that the new model was simple, realistic, and exhibited strong predictability. In addition to providing an accurate assessment of soil productivity, our model could potentially be applied as a soil module in comprehensive crop models.     

基于LUR的二氧化氮浓度空间分布模拟及其下垫面影响因素分析

随着经济的快速发展,空气污染已经成为当今重要的环境问题,引起公众的广泛关注,二氧化氮（NO₂）作为主要的空气污染物之一,成为相关研究的重点。通过监测数据发现,二氧化氮质量浓度值的空间分布具有区域性差异,所以对其空间分布模拟,以及形成区域差异的下垫面影响因素分析,具有重要的研究价值。土地利用回归模型（Land-use Regression,LUR）是将统计方法中的回归模型与空间上的土地利用数据、监测数据和其他相关的地理数据结合分析并在地图上显示的方法。本文结合缓冲区分析、叠加分析、Spearman相关性分析、多元回归分析等方法构建土地利用回归模型（Land Use Regression,LUR）,用于识别与NO₂浓度相关的下垫面影响因素,并模拟NO₂质量浓度的空间分布。LUR模型可以模拟出NO₂质量浓度空间分布特征,并针对下垫面影响因素得到以下结论：城乡居住地及工业用地面积增加、污染源的距离减少和道路长度增加会导致NO₂浓度升高;耕地面积、绿地面积和水域面积的增加会导致NO₂浓度减少;NO₂浓度最高的区域主要集中在工业园区;NO₂浓度值从城区到郊区递减,需要通过改变工业区结构和增加绿地面积来减少城区的NO₂浓度。