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针对变形发展趋势多样性的特点,将无偏NGM(1,1,k)模型应用于变形监测数据的分析预测中,说明无偏NGM(1,1,k)模型可分别用于拟合近似线性-指数增长趋势变形序列、近似非齐次指数变形序列和近似齐次指数变形序列。根据监测数据的发展特点可选择适合的建模方法。实例分析结果显示,无偏NGM(1,1,k)模型具有良好的拟合和预测精度,可用于滑坡位移的分析预测中。 相似文献
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针对原始序列平滑处理和用直线斜率代替t=k+1/2时刻导数两方面的问题,该文在分析GM(1,1)建模过程和原理的基础上,应用中心逼近原理,提出了基于原始序列的灰色预测模型OGM(1,1)。对于严格呈指数增长趋势的原始序列,通过平滑处理使其更利于建模,再通过累减获得新的初始序列,建立OGM(1,1)模型。通过对高增长、低增长和缓慢递减3种类型实测数据序列验证分析,比较GM(1,1)、PGM(1,1)和OGM(1,1)3种模型在变形监测数据处理中的拟合和预测结果,结果表明OGM(1,1)模型拟合效果更好、预测精度更高。 相似文献
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选取某一基坑沉降监测点,该点11个周期的累计沉降量为近似非齐次指数增长序列,以Java为工具对该点进行编程计算,得到GM(1,1)、DGM(1,1)、间接DGM(1,1)3种模型的基坑沉降预测结果。对比分析发现,间接DGM(1,1)模型精度高于GM(1,1)和DGM(1,1)模型,其C值仅为0.01,且残差值增加缓慢,近似于一条水平线,实测值与预测值非常接近,适用范围广,弥补了另两种模型不能进行长期预测的缺憾。 相似文献
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基于 Markov 理论的加权非等距GM(1,1)预测优化模型 总被引:1,自引:0,他引:1
背景值的构造方法是影响加权非等距GM(1,1)预测模型的精度和适应性的关键因素。文中通过等分函数法构造新的背景值对传统的加权非等距GM(1,1)模型进行优化,优化后的模型使其同时适应于高增长指数序列和低增长指数序列,提高传统模型的预测精度和适应性能力。但是优化后的模型依然易受建模数据随机扰动影响。马尔科夫(Markov)模型具有削弱建模数据的随机扰动性的优势。基于此,将优化的加权非等距GM(1,1)模型和Markov理论有机结合,构建优化的加权非等距Markov-GM(1,1)预测模型。最后,结合秀山湖二期工程的变形实测数据,运用新陈代谢的计算模式进行预测验证。结果表明:优化的加权非等距Markov-GM(1,1)预测模型的拟合和预测精度都优于传统的加权非等距GM(1,1)预测模型,新的预测模型的适用性更强,具有实际的参考价值。 相似文献
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为了研究提高GM(1,1)模型预测精度的方法,本文首先讨论了GM(1,1)模型对初值的不敏感性和拟合预测序列增长率的恒定性;其次,根据GM(1,1)的性质提出新陈代谢反演预测的方法;最后,通过工程实例对比不同模型的预测精度。结果表明:GM(1,1)反演预测方法具有很高的预测精度,适用于沉降变形预测。 相似文献
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鉴于MGM(1,n)在预测过程中,不同变量的拟合及预测残差差距较大,本文将自适应回归模型引入到不同变量的残差估计中,对整体的残差起到平滑的作用,从而抑制了残差的上扬趋势,经过实例分析,残差自适应回归MGM(1,n)的预测精度得到了明显的提高。 相似文献
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Recent advances in accessibility research: Representation,methodology and applications 总被引:22,自引:0,他引:22
Mei-Po Kwan Alan T. Murray Morton E. O'Kelly Michael Tiefelsdorf 《Journal of Geographical Systems》2003,5(1):129-138
In this article we examine recent advances in accessibility research and their implications for future studies. We base our
discussion on three intersecting dimensions that are useful for evaluating the contribution of recent studies: representation,
methodology and applications. Various examples are selected to show that research concerned with representation and methodological
problem solving is often applied to issues of broad concern in policy and planning. It is, however, not clear that the simultaneous
treatment of representation, methodological and application issues has ever been fully worked out. The questions raised in
this article may serve as a foundation for addressing issues pertinent to accurate representation, improved model building,
and more rigorous applications in accessibility research.
Received: 9 December 2002 / Accepted: 10 February 2003 相似文献
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变异时序回归GM(1,1)模型 总被引:1,自引:0,他引:1
鉴于在GM(1,1)预测模型中,灰参数与背景值导致的GM(1,1)模型的残差,本文提出将残差引入到时序中,对时序进行变异,利用不同的曲线回归方程对变异时序进行估计.基于对不同回归方程估计结果的误差分析,选用最佳的回归方程作为GM(1,1)变异时序预测方程;并将预测结果作为GM(1,1)模型的变量k.实例计算表明,变异时... 相似文献
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本文给出了北斗三号全球导航卫星系统定位导航授时、星基增强、精密单点定位、区域短报文通信、全球短报文通信和国际搜救共6类服务的测试评估方法,并利用实测数据对各类服务的核心指标进行了评估。结果表明,定位导航授时服务方面,空间信号测距误差0.23 m(RMS),空间信号可用性99.44%,空间信号连续性99.99%,PDOP可用性100%,B1C信号全球定位精度水平方向1.31 m、垂直方向2.13 m(95%),B1C信号全球定位可用性99.93%,B1C信号授时精度14.7 ns(95%);星基增强服务方面,定位精度水平方向1.03 m、垂直方向2.60 m(95%)、具有垂直引导能力的一类进近(APV-I)可用性100%;精密单点定位服务方面,定位精度水平方向0.17 m(95%)、垂直方向0.22 m(95%)、平均收敛时间9 min;区域短报文通信服务成功率99.6%,服务容量1530万次/h(上行)、935万次/h(下行);全球短报文通信服务成功率96.46%,服务容量40万次/h(上行)、21万次/h(下行);国际搜救服务方面,搜救信号接收成功率98.3%(发射功率37 dBm)。 相似文献
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O.R. van Lier J.E. Luther D.G. Leckie W.W. Bowers 《International Journal of Applied Earth Observation and Geoinformation》2011
Monitoring ecological indicators is important for assessing impacts of human activities on ecosystems. A means of identifying and applying appropriate indicators is a prerequisite for: environmental assessment; better assessment and understanding of ecosystem health; elucidation of biogeochemical trends; and more accurate predictions of future responses to global change, particularly those due to anthropogenic disturbance. The challenge is to derive meaningful indicators of change that capture the complexities of ecosystems yet can be monitored consistently over large areas and across time. In this study, methods for monitoring indicators of land cover (LC) and forest change were developed using multi-sensor Landsat imagery. Mapping and updating procedures were applied to the Humber River Basin (HRB) in Newfoundland and Labrador, one of four test sites in Canada selected for testing the development of national-scale methods. Procedures involved unsupervised clustering and labeling of baseline imagery, followed by image-to-image spectral clustering to derive binary change masks within which new LC types were classified for non-baseline imagery. Updated maps were compatible with the baseline map and reflected change in LC for three time periods: 1976–1990, 1990–2001, and 2001–2007. From the LC products, several change indicators were quantified including: forest depletion, forest regeneration, forest change, net forest change, and annual rates of change. The procedures were validated using field plots to assess the accuracy of the 2007 LC product (74.2% for 10 LC classes) and change classes observed from 2001 to 2007 (87.8% for four change classes: depletion, regeneration, non-treed class no change, and treed class no change). Methods were considered to be highly efficient and operationally feasible over large areas spanning multiple Landsat scenes. Specific results for the test site provided trend information supporting land and resource management in the HRB region. 相似文献
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Aloys Borgers Frank Hofman Maarten Ponjé Harry Timmermans 《Journal of Geographical Systems》2001,3(4):347-367
None of the currently developed activity-based models of transport demand explicitly models task allocation among household
members. To fill this gap, the present paper suggests to complement activity-based models of activity scheduling with a context-dependent
model of task allocation. That is, it is assumed that the allocation of tasks within households is partly based on such contextual
variables as the amount of time a member has to spend on mandatory activities and car availability. In particular, the paper
advocates a conjoint-based approach, based on an assignment task as opposed to the traditional ranking, rating or choice response
formats. By definition, an assignment task involves a combinatorial explosion of choice alternatives, implying that additional
operational decisions to estimate the context-dependent model are required. This study presents the results of various numerical
experiments, conducted to better understand the impacts of those decisions on the degree of bias in the parameter estimates
of the choice model. The results of these simulations indicate that under particular assumptions, the development and estimation
of a conjoint-based, context-dependent model of task allocation within households is feasible.
Received: March 1999 / Accepted: June 2001 相似文献
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时变参数PGM(1, 1)变形预测模型及其应用 总被引:7,自引:1,他引:7
汪孔政 《武汉大学学报(信息科学版)》2005,30(5):456-459
在GM(1,1)模型的基础上,考虑参数随时间的变化,用多项式逼近模型参数,同时针对GM(1,1)模型背景值取值方法的不足,引入背景值最佳生成系数,建立了时变参数PGM(1,1)变形预测模型。多项式中的待定系数采用最小二乘法确定,背景值最佳生成系数采用搜索法确定。实例计算表明,时变参数PGM(1,1)变形预测模型具有较高的模拟精度和预测精度,适合用于变形体的变形预测。 相似文献
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