共查询到18条相似文献，搜索用时 78 毫秒
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刘彦宾 《廊坊师范学院学报(自然科学版)》2009,9(3):27-29
在分析R-树空间索引结构的基础上,采用聚类分析的方法,对R-树空间索引进行研究,提出一种基于聚类分析的R-树节点分裂算法,提高了空间查询效率,并通过仿真实验,验证该算法的有效性。 相似文献
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空间数据库的索引是提高空间数据库存储效率、空间检索性能的关键技术．在综述现有空间数据库索引技术的基础上，对比分析R树、R＋树和R^＊树索引，认为R^＊树索引可获得较高的结点存贮利用率，还可以避免结点的分裂．最后给出了R^＊树索引在VisualTopo软件中的应用实例． 相似文献
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Skyline查询就是要查找数据集中不被其他点支配的所有点。由于Skyline查询在涉及多维空间数据库的应用领域中起着非常重要的作用,因而Skyline的计算受到了很大关注,特别是无需访问所有的数据点就能很快的返回Skyline点的算法。论文研究一种基于最近邻法Skyline查询方法,并对其作了分析。算法采用了R-树及堆结构,通过对目标数据集进行索引,存放最可能为Skyline点的数据于算法优先扫描的位置,这使得算法能高效计算出数据集的Skyline;同时,算法所采用的分枝界定法可以使所访问的空间数据点数目大大减少;再者,算法扫描一个点时,只需和当前已发现的Skyline点进行比较即能判断该点是否为Skyline点,保证了算法的渐进性。 相似文献
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空间索引在GIS数据的组织和检索中具有重要的作用,研究者对空间索引技术进行了广泛的研究,提出了许多索引算法。本文首先对目前空间索引技术的研究现状进行了介绍,然后从索引结构、索引操作算法的角度对典型的空间索引技术进行了分类阐述和对比分析,同时对它们的性能进行了评价,并指出了改进的思路。 相似文献
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针对B~ 树在索引文件方面的特点和优势,对B~ 树的结构和算法进行了分析和比较,并详细比较了具体应用中结构设计和算法选取的几种方案。 相似文献
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通过对数据库分层访问优化算法的设计,提高大型数据库的数据调度和信息索引能力。传统方法对分层数据库的访问算法采用语义指向索引技术,随着数据量的增大和干扰数据增多,对数据库访问的准确度不高。提出一种基于多维索引树编码的数据库分层访问技术,对大型分层Web数据库的数据结构模型进行系统分析,然后构建数据库中的数据信息流模型,以此为信息源进行多维索引树编码设计与数据库的语义信息特征模板匹配,实现对数据库的分层访问优化设计。仿真结果表明,采用该方法进行数据库分层访问,通过多维索引树编码,可提高数据库访问过程中的数据召回率和配准率,数据库访问的收敛性和抗干扰性较好,训练时间较短。 相似文献
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《洛阳师范学院学报》2015,(8):65-67
本文在分析经典Apriori算法和FP-growth算法存在问题的基础上,提出了一种基于索引数组的频繁项集挖掘算法.该算法以Apriori算法为基础,通过引入索引数组,有效缩小了候选集的范围,同时,因无需要采用FP树的存储结构,节省内存.通过实验性能分析比较,该算法可以有效提高频繁项集挖掘效率. 相似文献
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多值结点平衡二叉树的结构及算法研究 总被引：1，自引：0，他引：1
朱小明 《浙江教育学院学报》2004,(2):72-75
综合B_树和AVL树的优点,提出了一种新的数据结构MAVL树,它的优点是在保证运算高效的情况下最大限度地节约其作为索引结构时的存储空间,很适合在内存中使用.同时给出了基于MAVL树的基本算法. 相似文献
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对象关系数据库系统PostgreSQL提供的索引类型有:B-tree,R-tree,GiST和Hash。每种索引提供了适合不同查询类型的最优算法,而其中在大多数情况下都能适用,尤其适用于已经排好序的数据上的等值查询和范围查询。本文以最常用的B树索引为例,对PostgreSQL系统索引机制的建立进行了分析和探讨。 相似文献
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Jean Langlois Christian Bellemare Josée Toulouse George A. Wells 《Anatomical sciences education》2020,13(1):71-79
Spatial abilities have been correlated to anatomy knowledge assessment and spatial training has been found to improve spatial abilities in previous systematic reviews. The objective of this systematic review was to evaluate spatial abilities training in anatomy education. A literature search was done from inception to 3 August 2017 in Scopus® and several databases on the EBSCOhost platform. Citations were reviewed and those involving anatomy education, an intervention, and a spatial abilities test were retained and the corresponding full-text articles were reviewed for inclusion. Before and after training studies, as well as comparative training programs, relating a spatial training intervention to spatial abilities were eligible. Of the 2,405 citations obtained, 52 articles were identified and reviewed, yielding eight eligible articles. Instruction in anatomy and mental rotations training were found to improve spatial abilities. For the seven studies retained for the meta-analysis that included the effect of interventions on spatial abilities test scores, the pooled treatment effect difference was 0.49 (95% CI [0.17; 0.82]; n = 11) improvement. For the two studies that included the practice effect on spatial abilities test scores in a control group, the pooled treatment effect difference was 0.47 (95% CI [−0.03; 0.97]; n = 2) improvement. In these two studies, the impact of the intervention on spatial abilities test scores was found despite the practice effect. Evidence was found for improvement of spatial abilities in anatomy education using instruction in anatomy and mental rotations training. 相似文献
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Rats experienced a spatial pattern of baited and unbaited arms in an eight-arm radial maze. The spatial pattern remained constant
over trials, but the spatial locations that were baited varied unpredictably. Although there was no evidence of control by
the spatial pattern during free choice training trials, the rats’ ability to locate baited arms in forced choice test trials
was superior to that of animals in a control condition for which maze arms were not baited in a consistent spatial pattern.
This is consistent with the results of experiments showing that spatial choices by rats in a pole box maze are controlled
by abstract spatial patterns. 相似文献
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Jean Langlois Christian Bellemare Josée Toulouse George A. Wells 《Anatomical sciences education》2017,10(3):235-241
Anatomy knowledge has been found to include both spatial and non‐spatial components. However, no systematic evaluation of studies relating spatial abilities and anatomy knowledge has been undertaken. The objective of this study was to conduct a systematic review of the relationship between spatial abilities test and anatomy knowledge assessment. A literature search was done up to March 20, 2014 in Scopus and in several databases on the OvidSP and EBSCOhost platforms. Of the 556 citations obtained, 38 articles were identified and fully reviewed yielding 21 eligible articles and their quality were formally assessed. Non‐significant relationships were found between spatial abilities test and anatomy knowledge assessment using essays and non‐spatial multiple‐choice questions. Significant relationships were observed between spatial abilities test and anatomy knowledge assessment using practical examination, three‐dimensional synthesis from two‐dimensional views, drawing of views, and cross‐sections. Relationships between spatial abilities test and anatomy knowledge assessment using spatial multiple‐choice questions were unclear. The results of this systematic review provide evidence for spatial and non‐spatial methods of anatomy knowledge assessment. Anat Sci Educ 10: 235–241. © 2016 American Association of Anatomists. 相似文献
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介绍了GIS发展过程中出现的空间数据模型,以及不同空间数据模型的优缺点.对Geodatabase版本控制原理进行了分析说明,提出了使用版本控制来管理空间数据库的多用户并发操作、长事务处理,从而保证空间数据库的完整一致性.为建立和管理多用户的基于Geodatabase数据模型的空间数据库提供参考. 相似文献
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Victoria A. Roach Misa Mi Jason Mussell Sonya E. Van Nuland Rebecca S. Lufler Kathryn M. DeVeau Stacey M. Dunham Polly Husmann Hannah L. Herriott Danielle N. Edwards Alison F. Doubleday Brittany M. Wilson Adam B. Wilson 《Anatomical sciences education》2021,14(3):317-329
Interest in spatial ability has grown over the past few decades following the emergence of correlational evidence associating spatial aptitude with educational performance in the fields of science, technology, engineering, and mathematics. The research field at large and the anatomy education literature on this topic are mixed. In an attempt to generate consensus, a meta-analysis was performed to objectively summarize the effects of spatial ability on anatomy assessment performance across multiple studies and populations. Relevant studies published within the past 50 years (1969–2019) were retrieved from eight databases. Study eligibility screening was followed by a full-text review and data extraction. Use of the Mental Rotations Test (MRT) was required for study inclusion. Out of 2,450 screened records, 15 studies were meta-analyzed. Seventy-three percent of studies (11 of 15) were from the United States and Canada, and the majority (9 of 15) studied professional students. Across 15 studies and 1,245 participants, spatial ability was weakly associated with anatomy performance (rpooled = 0.240; CI at 95% = 0.09, 0.38; P = 0.002). Performance on spatial and relationship-based assessments (i.e., practical assessments and drawing tasks) was correlated with spatial ability, while performance on assessments utilizing non-spatial multiple-choice items was not correlated with spatial ability. A significant sex difference was also observed, wherein males outperformed females on spatial ability tasks. Given the role of spatial reasoning in learning anatomy, educators are encouraged to consider curriculum delivery modifications and a comprehensive assessment strategy so as not to disadvantage individuals with low spatial ability. 相似文献
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Three experiments tested human participants on a two-dimensional, computer, landmark-based search task to assess the integration
of independently acquired spatial and temporal relationships. Experiment 1 showed that A-B spatial training followed by B-outcome
spatial training resulted in spatial integration in such a way that A was effectively associated with the outcome. Experiment
2 showed that A-B spatial and temporal training followed by B-outcome spatial and temporal training resulted in integration
that created both spatial and temporal relationships between A and the outcome. Experiment 3 refuted an alternative explanation,
one that is based on decision-making speed, to the temporal-integration strategy that was suggested by Experiment 2. These
results replicate in humans the observations regarding spatial integration made by Sawa, Leising, and Blaisdell (2005) using
a spatial-search task with pigeons, and they extend those observations to temporal integration. 相似文献
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Studies have indicated the important impact of spatial abilities on science, technology, engineering, and mathematics (STEM) achievement. However, little is known about the predictors of individual differences in the growth trajectory of spatial ability. Children’s interest in learning activities plays a significant role in their ability development in literacy, math, and science. Therefore, the current study explored the role of children’s interest in spatial activities in their spatial ability development. We hypothesized that children’s interest in spatial activities would positively predict both the initial level and subsequent growth rate of spatial ability. The spatial ability of 197 Hong Kong preschool children (mean age = 52.72 months and SD = 3.30 months in the first wave of spatial ability assessment [Time 1]) was assessed four times over a two-year period, using a visual–spatial skills task. Their mothers ranked the children’s interest in various activities from 1 (most interested) to 13 (least interested) at Time 1. A growth curve analysis was performed to examine the relationships between interest in spatial activities at Time 1 and initial level and subsequent growth of spatial skills, controlling for parents’ expectations concerning spatial development, children’s interest in art activities, and demographics. The results showed that children’s interest in spatial activities significantly predicted their spatial ability growth (β = 0.252, p = .042), explaining 5.7% of the variance in growth, but was unrelated to the initial level of spatial skills. This finding highlights the importance of preserving and enhancing young children’s interest in spatial activities, among other activities, for the development of their spatial abilities. 相似文献