STGI:a spatio-temporal grid index model for marine big data

Marine big data are characterized by a large amount and complex structures,which bring great challenges to data management and retrieval.Based on the GeoSOT Grid Code and the composite index structure of the MongoDB database,this paper proposes a spatio-temporal grid index model(STGI)for efficient optimized query of marine big data.A spatio-temporal secondary index is created on the spatial code and time code columns to build a composite index in the MongoDB database used for the storage of massive marine data.Multiple comparative experiments demonstrate that the retrieval efficiency adopting the STGI approach is increased by more than two to three times compared with other index models.Through theoretical analysis and experimental verification,the conclusion could be achieved that the STGI model is quite suitable for retrieving large-scale spatial data with low time frequency,such as marine big data.

Grid System Analysis of Urban Flora of Bukhara City (Uzbekistan)

This article presents information on the study of the flora of Uzbekistan based on grid system mapping. The urban flora of the city of Bukhara was researched in it. As a result of research, the territory of Bukhara city was divided into 85 indexes based on 1 × 1 km2 grid mapping system. The diversity and density of species in the indexes are determined. The influence of anthropogenic factors on the diversity of species in the indexes is determined.

Research on Security Assessment Index System for Operating Reserve in Large Interconnected Power Grid

Optimization and placement of spinning reserve is an important issue in power system planning and operation. Systematic way for security assessment of operating reserve needs to study. A security assessment index system for operating reserve in large interconnected power grids is presented in this paper. Firstly, classification and determination methods of operating reserve at home and abroad are investigated, and operating reserve is divided into transient state operating reserve and quasi-steady state operating reserve from the view of security assessment. Secondly, assessment indexes and optimization methods for transient state operating reserve are studied. Thirdly, optimization model, deterministic and probabilistic optimization methods for quasi-steady state operating reserve are explored. Finally, some principles for determination of operating reserve are suggested, and a security assessment index system is put forward. The proposed index system, considering both transient and quasi-steady state, both deterministic and probabilistic methods, provides a systematic way to assessment and arrangement of operating reserve.

具有可用性改善的P-Grid覆盖网络

原P-Grid覆盖网络通过大量冗余将低在线率的节点构建成高可用性的系统.考虑分布式环境下节点不一定具有低在线率而呈现周期性,提出一种基于P-Grid的具有可用性改善的节点周期性组织方式.分类节点为长期节点、周期节点和普通节点,将长期节点按原P-Grid方式形成周期性组织下的主体二叉树,设计适当的信息表结构建立节点间的关系,并给出相应的查找、节点加入和数据对象创建的算法.数值分析和模拟实验表明在相同的节点规模及树高度下,周期性组织方式可以达到更高的可用性,同时数值分析也表明不影响维护消耗.

VFP中Grid控件使用技巧三则

介绍了 Grid 控件的一些使用技巧，用它可设计出不同的编辑和游览数据的窗口。

Index-Peer:半结构化网格资源发现模型

针对网格环境下的集中式和无结构P2P资源发现机制的不足,提出一个基于半结构化P2P索引技术的资源发现模型。该模型采用三层索引结构,模型充分利用网格环境中的节点性能差异,具有高效的查找功能,且对网络的高度动态性有良好的适应性。

Effects of mesh style and grid convergence on numerical simulation accuracy of centrifugal pump

In order to evaluate the effects of mesh generation techniques and grid convergence on pump performance in centrifugal pump model, three widely used mesh styles including structured hexahedral, unstructured tetrahedral and hybrid prismatic/tetrahedral meshes were generated for a centrifugal pump model. And quantitative grid convergence was assessed based on a grid convergence index(GCI), which accounts for the degree of grid refinement. The structured, unstructured or hybrid meshes are found to have certain difference for velocity distributions in impeller with the change of grid cell number. And the simulation results have errors to different degrees compared with experimental data. The GCI-value for structured meshes calculated is lower than that for the unstructured and hybrid meshes. Meanwhile, the structured meshes are observed to get more vortexes in impeller passage.Nevertheless, the hybrid meshes are found to have larger low-velocity area at outlet and more secondary vortexes at a specified location than structured meshes and unstructured meshes.

A novel decomposition and coordination algorithm for complex networks and its application to power grids

To analyze and control complex networks effectively, this paper puts forward a new kind of scheme, which takes control separately in each area and can achieve the network’s coordinated optimality. The proposed algorithm is made up of two parts: the first part decomposes the network into several independent areas based on community structure and decouples the information flow and control power among areas; the second part selects the center nodes from each area with the help of the control centrality index. As long as the status of center nodes is kept on a satisfactory level in each area, the whole system is under effective control. Finally, the algorithm is applied to power grids, and the simulations prove its effectiveness.

Differentiation degree combination weighting method for investment decision-making risk assessment in power grid construction projects

Power grid construction projects are distinguished by their wide variety,high investment,long payback period,and close relation to national development and human welfare.To improve the investment accuracy in such projects and effectively prevent investment risks,this paper proposes an investment optimization decision-making method for multiple power grid construction projects under a certain investment scale.Firstly,an in-depth analysis of the characteristics and development requirements of China’s power grid projects was performed.Thereafter,the time sequence and holographic method was adopted to conduct multi-dimensional,multi-perspective risk assessment of different parts of power grid projects,and a holographic risk assessment index system was developed.Moreover,an investment decision model considering the comprehensive risk based on combination weighting was developed according to the output and input of power grid construction projects.A new combination weighting optimization method that takes into account the investment willingness of enterprises was designed to improve the current weighting evaluation methods.Finally,the validity and applicability of the proposed evaluation method were verified by case examples.

Square Grid结构无线传感网数据传输的源路由策略分析

无线传感网中的汇聚传输模式使得靠近汇聚点的节点承担了较多的数据转发业务,导致这些节点能量很快耗尽,造成网络节点负载分布不均衡。针对这种汇聚传输问题,结合规则拓扑结构的对称性和预知性,提出基于Square Grid规则拓扑结构中分析典型源路由策略,设计一种计算路由节点负载分布的转发指数,并依据该转发指数分析各路由策略负载性能的方法。通过Mathematica绘制各路由节点负载分布图并对比各路由策略的转发指数,实验结果验证了Balancing Forwarding路由策略的节点具有较均衡的负载分布。该方法能有效地应用于评价路由策略的优劣。

Operating Analysis and Data Mining System for Power Grid Dispatching

The dispatching center of power-grid companies is also the data center of the power grid where gathers great amount of operating information. The valuable information contained in these data means a lot for power grid operating management, but at present there is no special method for the management of operating data resource. This paper introduces the operating analysis and data mining system for power grid dispatching. The technique of data warehousing online analytical processing has been used to manage and analysis the great capacity of data. This analysis system is based on the real-time data of the power grid to dig out the potential rule of the power grid operating. This system also provides a research platform for the dispatchers, help to improve the JIT (Just in Time) management of power system.

Modelling Three-Dimensional Winds on a NW Pacific Region of Mexico Using Boundary-Fitted Grids

In this study, the momentum equations describing an atmospheric flow over a NW Pacific region of Mexico are solved numerically. In order to capture the complex flow-topography interactions with detail, a combination of a numerical wind model in full 3D curvilinear coordinates, along with a high resolution boundary-fitted grid is used. Boundary conditions were obtained from ten years (2002-2012) of measured offshore wind data. Prevailing winds from April to September during that period of observations were selected for the simulations. For the cases analyzed, it was found that at the points of the study region (PSS, PSM, PM), wind speed increased about 10% to 20% of its offshore values, while inland they decreased about 86% to 96%. This spatial behavior agreed very well with the observed local winds. A coastal jet (CJ), 35 km long with speeds about 1.5 - 2 m/s, emanating from PSS was found for NNW winds. Modeled winds were also used to compute wind stresses, wind stress curl, and CUI fields. Wind stress values agreed very well to those reported in the literature. High values of wind stress curl, and CUI were found at the lee of the points (PSS, PSM, PM). Indirect estimations of sea surface currents were about 15 - 20 cm/s offshore and 5 - 10 cm/s at the coast.

Numerical Modelling of the Topographic Wetness Index: An Analysis at Different Scales

A variety of landscape properties have been modeled successfully using topographic indices such as topographic wetness index (TWI), defined as ln(a/tanβ), where a is the specific upslope area and β is the surface slope. In this study, 25 m spatial resolution from digital elevation models (DEM) data were used to investigate the scale-dependency of TWI values when converting DEMs to 50 and 100 m. To investigate the impact of different spatial resolution, the two lower resolution DEMs were interpolated to the original 25 m grid size. In addition, to compare different flow-direction algorithms, a second objective was to evaluate differences in spatial patterns. Thus the values of TWI were compared in two different ways: 1) distribution functions and their statistics;and 2) cell by cell comparison of DEMs with the same spatial resolution but different flow- directions. As in previous TWI studies, the computed specific upstream is smaller, on average, at higher resolution. TWI variation decreased with increasing grid size. A cell by cell comparison of the TWI values of the 50 and 100 m DEMs showed a low correlation with the TWI based on the 25 m DEM. The results showed significant differences between different flow-diretction algorithms computed for DEMs with 25, 50 and 100 m spatial resolution.

Application of SVR Models in Stock Index Forecast Based on Different Parameter Search Methods

Stock index forecast is regarded as a challenging task of financial time-series prediction. In this paper, the non-linear support vector regression (SVR) method was optimized for the application in stock index prediction. The parameters (C, σ) of SVR models were selected by three different methods of grid search (GRID), particle swarm optimization (PSO) and genetic algorithm (GA).The optimized parameters were used to predict the opening price of the test samples. The predictive results shown that the SVR model with GRID (GRID-SVR), the SVR model with PSO (PSO-SVR) and the SVR model with GA (GA-SVR) were capable to fully demonstrate the time-dependent trend of stock index and had the significant prediction accuracy. The minimum root mean square error (RMSE) of the GA-SVR model was 15.630, the minimum mean absolute percentage error (MAPE) equaled to 0.39% and the correspondent optimal parameters (C, σ) were identified as (45.422, 0.012). The appreciated modeling results provided theoretical and technical reference for investors to make a better trading strategy.

基于差分隐私的路网环境skyline查询

路网中的skyline查询在智慧交通、兴趣点发现和位置服务等领域具有重要的应用价值,但存在查询效率较低、未考虑查询结果的隐私性等问题。有鉴于此,文中提出了一种基于差分隐私的路网环境下skyline查询方法。首先,针对路网环境下的初始数据集数据量大和数据复杂的特点,对数据集进行预处理,利用基于距离属性划分的skyline层和路网Voronoi图的性质提出了3个剪枝规则,基于剪枝规则给出了路网环境下的数据集剪枝算法,从而有效地过滤掉大量冗余数据;其次,针对过滤后的数据集,利用网格索引的存储方式来节省存储空间,并设计了基于网格索引的skyline扩展树,基于扩展树和相应的剪枝规则提出了查询全局候选skyline点集的算法;最后,针对查询结果集,利用差分隐私预算分配模型来分配隐私预算,并基于信息散度进行结果集发布,有效提高了数据信息的隐私性。实验结果表明:所提出的查询方法的准确率在99%以上;其在数据集规模较大情况下的查询效率相较于传统skyline查询方法提升10%以上;在总差分隐私预算为0.01、0.10、0.50和1.00时,所提出的隐私预算分配方法的相对误差均低于等差分配和等比分配方法。

基于风雨综合指数的安徽省台风灾害房屋风险评估方法

台风致灾因子具有多重性,相对于其他灾种其风险评估更加复杂。采用安徽省81个国家气象站及1035个区域气象站台风过程逐日降水量、最大风速资料,构建台风风雨综合指数;利用台风风雨综合指数及孕灾环境影响系数,开展台风致灾危险性评估;基于自然灾害风险系统理论,综合致灾危险性、承灾体暴露度和脆弱性信息,评估安徽省台风灾害房屋风险。结果表明:影响安徽省台风年均个数为1.9个,持续天数以2~4 d居多;台风降水南部多于北部、山区多于平原。台风致灾高危险区位于皖南山区和大别山区,较高危险区位于江淮之间东部,低危险区位于沿淮淮北大部及江淮之间西北部。台风灾害房屋高及较高风险区主要分布在大别山区、江淮之间东部及皖南山区,这些区域海拔总体较高,台风过境易引发山洪地质灾害,加之房屋脆弱性较高,房屋倒塌及损毁风险高;中等风险区位于沿淮至江淮之间、江南部分地区,呈零星分布;较低和低风险区位于淮河以北中西部、沿江部分地区及城市主城区。利用全省各县区台风造成的房屋倒损数据,从空间一致性及散点相关对区划结果进行验证得到,区划结果与灾损具有高度的空间一致性,二者散点相关通过0.01的显著性水平检验,安徽省台风灾害房屋风险区划结果与实际情况基本吻合。

基于睿图中尺度模式的沈阳市防晒指数精细化预报

利用睿图中尺度模式输出的格点气象要素和与辐射相关的物理量逐小时数据,结合沈阳总辐射观测实况资料,利用多元回归方法,建立防晒指数精细化预报模型。结果表明:(1)睿图东北模式输出产品中,气象因子和辐射因子对比,辐射因子与太阳总辐射的相关性更好。其中地表高度向下的短波辐射通量和地面热通量与太阳总辐射的相关性最显著。(2)以综合因子建模方式,建立分季节的太阳总辐射预报方程。方程诊断分析表明,春季和冬季预报模型拟合度最高,稳定性最强。全年预报方程模型拟合度较高,夏、秋两季拟合度略差。(3)预报检验结果显示:春季防晒指数等级预测正确的比例为83.7%,夏季为87.4%,秋季为88%,冬季为96.9%。预测结果较为理想,可在防晒指数预报业务中使用。

A Multi-Agent Resource Selection Model in Manufacturing Grid Environment

A group of agents are intimately cooperated to set the assessment indices, establish the weight of each index in overall result of evaluation, collect the experts＇ scores given to each available resource, and the manufacturing resource whose overall assessment value is highest is taken as the optimal choice. Architecture of the proposed system is outlined and an example is offered to show the process of accomplishing the assessment.

钢筋混凝土网格剪力墙双参数地震损伤模型及损伤分析

为了研究钢筋混凝土网格剪力墙在地震作用下的损伤演化规律,对已有钢筋混凝土构件双参数地震损伤模型进行修正,提出了适用于网格剪力墙的地震损伤模型;利用灰色关联方法,对网格剪力墙试验信息进行分析,确定关键设计参数,给出损伤模型中的组合系数计算公式。研究了剪跨比、轴压比、竖肢宽度和横肢高度等参数对网格墙损伤的影响,得到网格剪力墙主要影响参数与损伤演化的关系。基于所提出的损伤模型,计算了网格剪力墙的损伤指数,根据网格剪力墙构件破坏程度将其划分为基本完好、轻微破坏、中度破坏、严重破坏和倒塌失效5个损伤等级,标定了不同损伤等级的损伤指数区间。

基于衰减指数的主动配电网纵联保护新方法研究

根据光伏并网系统中光伏与大系统电源故障输出特性的差异,提出一种基于电流衰减指数的主动配电网保护新原理.首先对采集的保护线路首、末端电流进行滤波、去噪,以避免噪声造成Prony计算不精确的问题;再将线路首、末端电流衰减指数作差与给定门槛值比较,以便判断故障区域;最后通过改变故障位置、故障距离以及光伏渗透率,验证该方法在不同情况下的适用性.通过Matlab仿真实验表明本文提出的方法能够准确判断线内、线外故障,并且其对判断故障相有一定效果.