轨迹大数据: 数据处理关键技术研究综述

针对轨迹大数据的高效点-轨迹k近邻（point to trajectory k nearest neighbor, P2T_kNN）查询处理需求,提出了一种融合时空剖分和轨迹分段的轨迹组织方法,其核心思想是在对轨迹作时间剖分的基础上,利用离散全球网格系统（discrete global grid system, DGGS）在空间上进行再次剖分,从而利用两次剖分得到的时空单元编码来索引落入其中的轨迹片段。在此基础上利用分布式列式存储技术设计了面向轨迹大数据的P2T_kNN查询处理框架,提出了一种顾及轨迹数据空间分布的自适应空间单元搜索算法,即通过分析轨迹数据在给定时间约束下的空间分异特征,动态调整空间单元的搜索步长,从而提升了轨迹稀疏区域的处理效率。针对亿级轨迹的实验结果表明,该方法适用于轨迹大数据的P2T_kNN查询处理,在轨迹稠密与稀疏区域的平均查询响应时间均小于1 s。     

深埋隧洞不同开挖方式下即时型岩爆微震信息特征及能量分形研究

基于锦屏二级水电站深埋隧洞钻爆法及隧道掘进机（TBM）开挖过程中大量微震监测数据及不同等级的岩爆案例,对不同开挖方式下即时型岩爆的孕育及发生过程的能量释放展开研究,并运用分形几何原理研究微震能量分布的变化规律,得到以下结论：（1）即时型岩爆的孕育及发生过程中,岩爆区围岩岩体处于破坏加速集聚并不断扩展的过程;（2）钻爆法开挖过程中储存在岩体内的弹性应变能消耗于岩体破裂过程大于TBM开挖,而转化为岩体动能小于TBM开挖;（3）钻爆法开挖微震能量分形维度在即时型岩爆的孕育过程不断增加,岩爆临近前会增加到某个临界值以上;（4）TBM开挖即时型高等级岩爆能量分形维度值大于钻爆法开挖,并且其分形维度值可以反映低等级岩爆伴随发生的特征。     

Sinkhole hazard assessment in Minnesota using a decision tree model

An understanding of what influences sinkhole formation and the ability to accurately predict sinkhole hazards is critical to environmental management efforts in the karst lands of southeastern Minnesota. Based on the distribution of distances to the nearest sinkhole, sinkhole density, bedrock geology and depth to bedrock in southeastern Minnesota and northwestern Iowa, a decision tree model has been developed to construct maps of sinkhole probability in Minnesota. The decision tree model was converted as cartographic models and implemented in ArcGIS to create a preliminary sinkhole probability map in Goodhue, Wabasha, Olmsted, Fillmore, and Mower Counties. This model quantifies bedrock geology, depth to bedrock, sinkhole density, and neighborhood effects in southeastern Minnesota but excludes potential controlling factors such as structural control, topographic settings, human activities and land-use. The sinkhole probability map needs to be verified and updated as more sinkholes are mapped and more information about sinkhole formation is obtained.     

水深测量成果相邻图幅拼接质量评估方法研究

在利用搜索重合点水深比对法检查相邻两水深测量成果拼接质量过程中,通过展现重合点在拼接区域的分布情况,发现搜索的重合点存在相对总点数较少且分布不均匀的缺点,影响评估质量.针对上述问题,建立了网格选取剖面比对法,系统阐述了该方法的操作原理及其应用并通过实例验证取得了较好的结果,为水深测量成果相邻图幅拼接质量评估提供新的思路.     

Ms 8.7印尼地震面波在云南产生的远场动态即刻触发特征

通过云南区域数字测震台网对2004年12月26日Ms 8.7印尼大震的波形记录，着重考查了大地震面波在到达云南26个台站后的1小时传播过程中对云南及周边地区产生的远场动态触发效应，发现在面波作用的短短1小时内，云南的西部地区有明显的地震即刻触发现象，并对这些现象的特征及其相关因素进行了讨论.     

横观各向同性土体有限层分析

首先概括介绍了三维横观各向同性比奥固结有限层分析方法,并采用已经发表的4个算例结果来考证所编制的计算程序,然后详细地讨论了横观各向同性对瞬时沉降、最终沉降和固结性状的影响,发现横观各向同性对计算结果的影响分别高达33 %,24 % 和40 %,最后给出了一些对工程实践有一定参考价值的计算图表。     

A neighbor decay cellular automata approach for simulating urban expansion based on particle swarm intelligence

Simulation and quantitative analysis of urban land use change are effective ways to investigate urban form evolution. Cellular Automata (CA) has been used as a convenient and useful tool for simulating urban land use change. However, the key issue for CA models is the definition of the transition rules, and a number of statistical or artificial intelligence methods may be used to obtain the optimal rules. Neighborhood configuration is a basic component of transition rules, and is characterized by a distance decay effect. However, many CA models do not consider the neighbor decay effect in cellular space. This paper presents a neighbor decay cellular automata model based on particle swarm optimization (PSO-NDCA). We used particle swarm optimization (PSO) to find transition rules and considered the decay effect of the cellular neighborhood. A negative power exponential function was used to compute the decay coefficient of the cellular neighborhood in the model. By calculating the cumulative differences between simulation results and the sample data, the PSO automatically searched for the optimal combination of parameters of the transition rules. Using Xiamen City as a case study, we simulated urban land use changes for the periods 1992–1997 and 2002–2007. Results showed that the PSO-NDCA model had a higher prediction accuracy for built-up land, and a higher overall accuracy and Kappa coefficient than the urban CA model based on particle swarm optimization. The study demonstrates that there exist optimal neighborhood decay coefficients in accordance with the regional characteristics of an area. Urban CA modelling should take into account the role of neighborhood decay.     

径向基函数神经网络需水预测研究

在分析山西省历年用水量和人均用水量的基础上，建立径向基函数神经网络需水预测模型，采用最近邻聚类学习算法确定径向基函数的宽度、选取聚类中心和权值。采用丰富的需水预测因子作为模型的输入，网络输出需水预测值。预测结果表明，径向基函数神经网络需水预测模型运算速度快，有较高的预测精度。需水预测可为水资源规划和配置提供依据。     

推荐系统中物品召回技术的研究进展

信息技术的快速发展导致信息过载.推荐系统是解决信息过载最有效的方式之一.近年来,深度学习的快速发展也带动了推荐系统的进步,各种深度推荐算法层出不穷.然而由于候选物品数量巨大且用户兴趣动态变化,深度推荐算法的推荐复杂度巨大,难以在实际系统中单独使用.在深度推荐技术发展的同时,物品召回技术（也称近似搜索技术）也有了较大的发展与进步.本文先介绍基于距离最小化的物品召回的研究进展,再从向量索引、局部敏感哈希、哈希学习、向量量化四个方面来深入探讨基于内积最大化的物品召回技术的研究进展.     

Statistical analysis of tectonic patterns in areal volcanism: The bunyaruguru volcanic field in West Uganda

A quantitative analysis was made of the spatial arrangement of 149explosion craters in the western rift of Uganda. A variety of methods demonstrate that the spatial pattern of the craters reveals significant structural patterns that have guided volcanism to the surface. It is shown that the east-west elements in the field affected location, and the main rift fault is resolved into two main components. Tentatively, a possible dextral transform fault is identified that affected the relative location of the two main zones of activity. Grouping techniques demonstrate that crater groups obey an exponential rank-size rule and allow a mapping of the craters into energy classes that reveals a concentric pattern of energy in the field. The effect of the topography on energy levels and crater size show that only topography greater than 11,000ft could have prevented all eruptive activity, but the smaller energies and craters are sensitive to height differences on the order of the height of the rift wall, about 1000ft. Total energy in each crater class size is roughly constant, and the field energy could create one or two single craters comparable in size to small central volcanoes.