基于显／隐式表达的时空模型分类

根据时空对象与时空拓扑关系的显/隐式表达模式,提出了一种新的时空数据模型的分类方法.将时空模型分为时空对象与时空关系,其中时空对象包括事件与状态两种原子,时空关系包括事件之间关系、状态之间关系、事件与状态之间关系等三种基本关系;时空表达分为显式、隐式、半显半隐式三种模式.基于显隐式表达的时空模型分类系统采用时空对象、时空关系与时空表达的三元组结构描述,并列举了典型的时空数据模型,为用户选择满足不同应用需求的时空模型提供了理论依据.

面向大数据的时空数据挖掘综述

时空数据挖掘是数据挖掘领域的前沿研究课题,正致力于开发和应用新兴的计算技术来分析海量、高维的时空数据,揭示时空数据中的有价值知识.本文以时空大数据为背景,介绍数据挖掘技术产生的背景与发展、时空数据挖掘的研究现状、研究内容、应用领域、面向大数据的时空数据挖掘系统架构以及实现技术,为相关领域的研究者提供参考.

试论花岗岩类的地质环境分类

对以往花岗岩类的地质环境分类分析，可以归纳出分别强调时间和空间作为分类原则的二大类，花岗岩类的岩石学特征及成因随时空环境而有规律演变，其地质环境分类的原则应同时包括时间和空间二大因素。在此基础上，提出了花岗岩类的时空分类。

利用SOFM网络评价杭州西湖水质的时空变化

根据西湖8个采样点2000年1月至12月的常规监测数据和多次模拟调试找出影响西湖水体的主要水质因子作为自组织人工神经网络的输入变量,利用网络的无差别分类能力,建立多指标水质综合评价的自组织特征映射网络(Self-Organizing Feature Map)模型,探索各个湖区不同时段的富营养化状况.结果表明,利用SOFM人工神经网络对西湖水体进行时空分类的结果直观、清晰,从空间上看,小南湖的水质较好,而北里湖的较差;从时间上看,一、二月份水质较好,五到十月份水质较差.说明人工神经网络模型能有效合理的模拟富营养化进程中的非线性行为,并能准确评价西湖水质的富营养化状况,为及时有效的提出控制措施提供科学的依据.

时空数据挖掘研究进展

近年来,随着全球定位系统、传感器网络和移动设备等的普遍使用,非时空数据和时空数据急剧增加,加之时空数据处理更为复杂,使数据处理任务日趋繁重的形势更加严峻.因此,寻找有效的时空数据挖掘方法具有十分重要的意义.针对这一背景,主要围绕时空模式发现、时空聚类、时空异常检测、时空预测、时空分类、时空数据挖掘与推理的结合等方面,对时空数据挖掘研究的现状进行了详细介绍,对其当前所面临的一些主要问题及可能的解决方案进行了探讨.

交通事故的时空热点分析

针对目前交通事故分析中时空维度分离的不足,以H市2013-2015年的交通事故数据为研究对象,根据自组织神经网络、平行坐标系、时空颜色矩阵和时空网络核密度估计、热点分析法,分别从行政区划以及道路网络上进行交通事故的时空特征分析,从宏观和微观角度揭示交通事故的时空热点区域。结果表明,整体来说,在空间上,H市交通事故热点区域4个街道高于8个镇,呈明显的“两带一中心”分布,即硖许线与101省道形成的带状区域和市政府所在的行政中心区域;时间上,早、晚高峰时段最为严重,夜晚较为轻微,呈明显的区域特征分布,即工业办公区热点出现在早高峰时段,生活住宅区热点出现在晚高峰时段,商业消费区热点出现在夜晚时段。

时空轨迹分类研究进展

时空轨迹分类旨在为一条轨迹预测类别。时空轨迹分类在城市规划、个性化用户推荐等方面具有重要应用价值,其过程主要包括轨迹数据预处理、特征提取、建立分类器3个阶段。本文综述了近年来时空轨迹分类的研究进展,首先对时空轨迹分类的过程进行概述;然后将时空轨迹分类算法按特征提取的方式分为基于运动特征的轨迹分类算法、基于分类规则的轨迹分类算法和基于图像信号分析的轨迹分类算法3类,分别论述了这些算法的基本思想和优缺点;之后对现有的轨迹分类算法从数据来源、分类器、特征提取方式等方面进行对比分析;最后讨论现有的时空轨迹分类算法面临的挑战。

Spatio-temporal Variations of Evapotranspiration in Anhui Province Based on MOD16 Products

Based on the MOD16 remote sensing product provided by NASA, the temporal and spatial distribution characteristics of evapotranspiration in Anhui Province from 2000 to 2014 were analyzed statistically with the support of ENVI remote sensing image processing system and ARCGIS .geographic information system. The results showed that： （1） The annual average ET in Anhui Province was 694.9 mm from 2000 to 2014, less than half of PET, indicating that Anhui Province as a whole was in dry climate and water shortage, particularly significant in 2011-2014, with the maximum value of 730.6 mm occurring in 2003, and the minimum value of 647.6 mm occurring in 2011. The monthly average ET and PET showed a single peak distribution pattern, ET peak appearing in August, and PET peak appearing in May. （2） Linear regression analysis of ET and PET showed that there was a signif- icant decrease trend in ET in Anhui Province from October to March of the following year, and in addition, there was also a decreasing trend in the summer from June to July, but PET for the whole year demonstrated an increasing trend. The change trends of both illustrated that drought in Anhui Province was becoming more and more serious. （3） The spatial distribution of ET and PET showed that Anhui Province had obvious characteristics of high in south and low in north, and the north had large yearly and monthly changes, while the south had relatively stable changes. （4） The evapotranspiration of different land use types showed different an- nual and monthly variation characteristics, and the overall expression of annual evapotranspiration was in the order of forest 〉 grassland 〉 farmland. In terms of the monthly change, monthly evapotranspiration was manifested as winter grassland larger than the forest, forest evapotranspiration gradually exceeding the grass, and the evapotranspiration gap among the three widening continuously until the peak appearing in July or August. Due to the seasonality of crop plantation and under the common action of temperature, precipitation and other sensitive factors, the monthly evapotranspiration of forest and grassland was of single peak distribution with the maximum appearing in July, and the monthly evapotranspiration of farmland showed double peak distribution, appearing respectively in May and August, the former being weaker than the latter in strength

Tourism Competitiveness Evaluation and Spatio-temporal Characteristics of Chinese Border Counties

Under the current government strategy of building a Silk Road economic belt, tourism in Chinese border counties has becoming increasingly popular. Studying tourism competitiveness in Chinese border counties is of sizable theoretical and practical importance, as there are several notable factors involved. In this study, we constructed a tourism competitiveness evaluation model based on eight factors: natural environment, tourism resource, location and transportation, social environment, tourism service facility, border port, tourism industrial cluster and tourism market. We then analyzed the spatial characteristics of tourism competitiveness in border counties and identified five types of border counties: resource advantage type(RA), border-port advantage type(PA), location advantage type(LA), agglomeration advantage type(AA), and relative balance type(RB), and examined the correlation between tourism market competitiveness and interior competitiveness factors in the counties from 2006 to 2011. Results showed that tourism resource, location and transportation, and tourism service facility are the most important competition factors for RA border counties during the study period. Competition factors in PA counties transferred from tourism resource, social environment and tourism service facility to border port and tourism industrial cluster; competition factors in LA counties transferred from natural environment and tourism resource to tourism service facility and tourism industrial cluster and border port. Competition factors in AA counties transferred from tourism service facility to tourism resource. Tourism industrial cluster, tourism service facility and tourism resource proved to be important competition factors in RB counties. The findings of this study can be used to target tourism strategies according to different county types.

Spatiotemporal distribution of protozooplankton and copepod nauplii in relation to the occurrence of giant jellyfish in the Yellow Sea

The occurrence of the giant jellyfish, Nemopilema nomurai, has been a frequent phenomenon in the Yellow Sea. However, the relationship between the giant jellyfish and protozoa, in particular ciliates, remains largely unknown. We investigated the distribution of nanoflagellates, ciliates, Noctiluca scintillans, and copepod nauplii along the transect 33~N in the Yellow Sea in June and August, 2012, during an occurrence of the giant jellyfish, and in October of that year when the jellyfish was absent. The organisms studied were mainly concentrated in the surface waters in summer, while in autumn they were evenly distributed in the water column. Nanoflagellate, ciliate, and copepod nauplii biomasses increased from early June to August along with jellyfish growth, the first two decreased in October, while N. scintillans biomass peaked in early June to 3 571 pg C/L and decreased in August and October. In summer, ciliate biomass greatly exceeded that of copepod nauplii （4.61-15.04 ~tg C/L vs. 0.34-0.89 pg C/L）. Ciliate production was even more important than biomass, ranging from 6.59 to 34.19 ~tg C/（L.d） in summer. Our data suggest a tight and positive association among the nano-, micro-, and meso-zooplankton in the study area. Statistical analysis revealed that the abundance and total production of ciliate as well as loricate ciliate biomass were positively correlated with giant jellyfish biomass, indicating a possible predator-prey relationship between ciliates and giant jellyfish. This is in contrast to a previous study, which reported a significant reduction in ciliate standing crops due to the mass occurrence ofN. nomurai in summer. Our study indicates that, with its high biomass and, in particular, high production ciliates might support the mass occurrence of giant jellyfish.

SPATIO-TEMPORAL VARIATION CHARACTERISTICS OF EXTREMELY HEAVY PRECIPITATION FREQUENCY OVER SOUTH CHINA IN THE LAST 50 YEARS

This paper comprehensively studies the spatio-temporal characteristics of the frequency of extremely heavy precipitation events over South China by using the daily precipitation data of 110 stations during 1961 to 2008 and the extremely heavy precipitation thresholds determined for different stations by REOF, trend coefficients, linear trend, Mann-Kendall test and variance analysis. The results are shown as follows. The frequency distribution of extremely heavy precipitation is high in the middle of South China and low in the Guangdong coast and western Guangxi. There are three spatial distribution types of extremely heavy precipitation in South China. The consistent anomaly distribution is the main type. Distribution reversed between the east and the west and between the south and the north is also an important type. Extremely heavy precipitation events in South China mainly occurred in the summer-half of the year. Their frequency during this time accounts for 83.7% of the total frequency. In the 1960 s and 1980 s, extremely heavy precipitation events were less frequent while having an increasing trend from the late 1980 s. Their climatological tendency rates decrease in the central and rise in the other areas of South China, and on average the mean series also shows an upward but insignificant trend at all of the stations. South China's frequency of extremely heavy precipitation events can be divided into six major areas and each of them shows a different inter-annual trend and three of the representative stations experience abrupt changes by showing remarkable increases in terms of Mann-Kendall tests.

Do physicochemical variables regulate the distribution of zooplankton communities in reservoirs dominated by filter-feeding carp?

The temporal and spatial distributions of zooplankton communities in the upper, middle, and lower reaches of the Xin＇anjiang Reservoir, Zhejiang, China, were investigated monthly, between 2009 and 2010. Silver carp （Hypophthalmichthys moBtrix） and bighead carp （Aristichthys nobilis） dominated the pelagic fish community of this large, deep reservoir. Cladocerans were distributed evenly throughout the reservoir. Rotifers were mainly found in the upper reaches, while copepods tended to assemble in the lower reaches. The Pearson correlation analysis and stepwise multiple regression were used to identify the major physicochemical gradients influencing community variations. Zooplankton community distributions were influenced by water temperature, dissolved oxygen, phosphorus, nitrogen, and silicon. Excess nutrients, in particular silicon, stimulated rotifer growth. Based on these findings, it is possible to use rotifer density as a bioindicator of eutrophic status in deep reservoir ecosystems.

Fusion of ERT Images Based on Dempster-Shafer's Evidence Theory

In this paper, an electrical resistance tomography(ERT) imaging method is used as a classifier, and then the Dempster-Shafer's evidence theory with fuzzy clustering is integrated to improve the ERT image quality. The fuzzy clustering is applied to determining the key mass function, and dealing with the uncertain, incomplete and inconsistent measured imaging data in ERT. The proposed method was applied to images with the same investigated object under eight typical current drive patterns. Experiments were performed on a group of simulations using COMSOL Multiphysics tool and measurements with a piece of porcine lung and a pair of porcine kidneys as test materials. Compared with any single drive pattern, the proposed method can provide images with a spatial resolution of about 10% higher, while the time resolution was almost the same.

The Late Miocene‘ovibovin’bovids in Eurasia

During the Late Miocene,numerous medium to large-sized herbivores,that resemble the living Ovibos in skeletal morphology,dispersed throughout the Holarctic realm and comprised eleven genera:Lantiantragus,Shaanxispira,Tsaidamotherium,Criotherium,Mesembriacerus,Hezhengia,Urmiatherium,Parurmiatherium,Plesiaddax,Sinotragus,and Prosinotragus.These genera are primarily found in eastern Asia,in which nine genera are found in northern China,as well as in countries in eastern Europe and western Asia.They are distinguished by unique characteristics,including a perpendicular braincase,specialized horn cores,and a robust basioccipital.Previous studies have often classified these‘ovibovin’bovids as part of the conventional subfamily/tribe Ovibovinae/Ovibovini,along with extant Ovibos.Nevertheless,an increasing number of studies do not support the monophyly of the subfamily/tribe Ovibovinae/Ovibovini,nor is a close relationship likely between these Late Miocene‘ovibovin’bovids and extant Ovibos.Among the eleven genera of‘ovibovin’bovids,Plesiaddax,Hezhengia,and Urmiatherium are often considered to have a very close relationship and conventionally form the tribe Urmiatheriini.However,previous phylogenetic analyses do not support the monophyly of Urmiatheriini.This paper presents a summary of the transmutation of the terms Ovibovidae/Ovibovinae/Ovibovini/Ovibovina,the temporal and spatial distribution of the Late Miocene‘ovibovin’bovids in Eurasia,the principal characteristics of these taxa,and the previous phylogenetic analyses.

Temporal dynamics of mental impasses underlying insight-like problem solving

Insight problem solving is characterized by mental impasses,states of mind in which the problem solver does not know what to do next.Although many studies have investigated the neural correlates of insight problem solving,however,the question when mental impasses occur during insight problem solving has been rarely studied.The present study adopted high temporal resolution ERPs to investigate the temporal dynamics of an impasse underlying insight problem solving.Time locked ERPs were recorded associated with problems with impasses(PWI) and problems without impasses(POI).The problem types were determined by participants' subjective responses.The results revealed an early frontocentral P2 was linked with the preconscious awareness of mental impasses and a P3a was associated with fixed attention when the impasse formed.These findings suggest the impasse may occur initially at a relatively early stage and metacognition plays an important role in insight problem solving.

Classification of Variational Conservation Laws of General Plane Symmetric Spacetimes

In this article we discuss Noether conservation laws admitted by a Lagrangian L = gab(dx^a/ds)(dx^b/ds)of a test particle moving in the field of a general plane symmetric non-static spacetime metric. In this context, we first present a general solution representing a Noether symmetry vector subject to differential constraints satisfied by the general plane symmetric non-static metric. We then use a class of plane symmetric non-static metrics obtained by Feroze et al. and discuss, in each case, Noether conservation laws in comparison with Killing symmetries.

Model-based analysis of spatio-temporal changes in land use in Northeast China

Spatially explicit modeling techniques recently emerged as an alternative to monitor land use changes. This study adopted the well-known CLUE-S(Conversion of Land Use and its Effects at Small regional extent) model to analyze the spatio-temporal land use changes in a hot-spot in Northeast China(NEC). In total,13 driving factors were selected to statistically analyze the spatial relationships between biophysical and socioeconomic factors and individual land use types. These relationships were then used to simulate land use dynamic changes during 1980–2010 at a 1 km spatial resolution,and to capture the overall land use change patterns. The obtained results indicate that increases in cropland area in NEC were mainly distributed in the Sanjiang Plain and the Songnen Plain during 1980–2000,with a small reduction between 2000 and 2010. An opposite pattern was identified for changes in forest areas. Forest decreases were mainly distributed in the Khingan Mountains and the Changbai Mountains between 1980 and 2000,with a slight increase during 2000–2010. The urban areas have expanded to occupy surrounding croplands and grasslands,particularly after the year 2000. More attention is needed on the newly gained croplands,which have largely replaced wetlands in the Sanjiang Plain over the last decade. Land use change patterns identified here should be considered in future policy making so as to strengthen local eco-environmental security.