基于GIS的库车县耕地土壤质量综合评价

土壤质量评价,是农业可持续发展研究的重要内容之一,对土地资源的科学利用和管理具有重要的现实意义。基于库车县实地采样数据,采用土壤质量指数综合评价模型(SQI),在ArcGIS地统计分析模块的支持下,对研究区土壤质量指数进行克里格(Kriging)空间插值。研究结果表明：库车县耕层土壤的质量指数多在0.3~0.6左右,少数区域的SQI值在0.3以下及0.6以上;在空间分布上,土壤质量指数总体上呈带状和斑块状分布,土壤综合质量在南北方向高于东西方向,且由绿洲中部向绿洲外围递减的变化趋势,研究区中部区域的土壤质量较周围区域的土壤质量好。     

Do coarse resolution U.S. presettlement land survey records adequately represent the spatial pattern of individual tree species?

Presettlement land survey records (PLSRs) are a valuable and unique source of information for the reconstruction of presettlement forest patterns. The purpose of this study was to determine whether coarsely resolved PLSRs are adequate to characterize the spatial patterns of individual tree species over large areas. The General Land Office Survey records of the PLSRs of Minnesota were used and species selected in the analysis were based on their abundances and degrees of clustering. A geostatistical procedure was developed to analyze observations of bearing-tree point-locations, at progressively coarser resolutions from 1×1 mile to 24×24 miles, to create spatially continuous probability surfaces of species occurrences across the landscape. Statistical and visual analyses of the geostatistical predictions indicated that coarsely resolved PLSRs, as coarse as 24×24 miles, can adequately represent the spatial pattern of individual species over large areas. Mean errors in predictions increased as more coarsely resolved data were used, primarily in response to the decreased abundance of a species and minorly in response to the degree of spatial clustering of a species. The results indicate that coarsely resolved township-level data of 6×6 miles can be used for presettlement vegetation reconstruction of large areas of several counties.     

农田土壤养分交换性镁的空间分布模拟方法比较——以昭阳区为例

采用反距离加权法、径向基函数插值法、克里格法、回归模型法,以云南省昭阳区农田土壤养分采样数据为对象,对全区土壤交换性镁含量进行模拟。结果表明,由于中量元素分布的复杂性,不同模拟方法得到的预测精度不同;反距离加权法强调空间距离权重的影响,未能较好的反应分布规律;径向基函数插值法由于采样点数据具有很大的不确定性,故效果也不理想;克里格法误差最小,精度最高;回归模型法误差较大,但最能反应农田土壤交换性镁分布的地域特征和立体变化特征。     

Testing the performance of spatial interpolation techniques for mapping soil properties

In this paper, we implement and compare the accuracy of ordinary kriging, lognormal ordinary kriging, inverse distance weighting (IDW) and splines for interpolating seasonally stable soil properties (pH, electric conductivity and organic matter) that have been demonstrated to affect yield production.The choice of the exponent value for IDW and splines as well as the number of the closest neighbours to include was decided from the root mean squared error (RMSE) statistic, obtained from a cross-validation procedure. Experimental variograms were fitted with the exponential, spherical, Gaussian and linear models using weighted least squares. The model with the smallest residual sum of squares (RSS) was further interrogated to find the number of neighbours that returned the best cross-validation result.Overall, all of the methods gave similar RMSE values. On this experimental field, ordinary kriging performed best for pH in the topsoil and lognormal ordinary kriging gave the best results when applied to electrical conductivity in the topsoil. IDW interpolated subsoil pH with the greatest accuracy and splines surpassed kriging and IDW for interpolating organic matter.In all uses of IDW, the power of one was the best choice, which may due to the low skewness of the soil properties interpolated. In all cases, a value of three was found to be the best power for splines. Lognormal kriging performed well when the dataset had a coefficient of skewness larger than one. No other summary statistics offered insight into the choice of the interpolation procedure or its parameters. We conclude that many parameters would be better identified from the RMSE statistic obtained from cross-validation after an exhaustive testing.     

自由曲面研抛加工的直接插补控制

研抛加工的目的是成型质量均恒的精密表面。基于自由曲面研抛加工的直接插补控制,本文就残留高度与研抛轨线间距、工具头半径、曲面曲率半径间的关系,插补误差与插补步长、工具头半径、曲面曲率半径间的关系等问题展开了讨论,揭示了其相关规律,并在此基础上给出了以许用误差为控制目标的研抛加工路径规划、插补综合控制策略。实验数据表明,该控制策略误差目标可控,误差控制效果明显。     

不同取样方式下土壤质地空间插值的精度分析

为研究土壤质地的合理取样方式,进而研究其空间变异情况,为田间施肥及灌溉提供依据,本试验利用地统计学方法和GIS技术,在重庆市彭水县重庆烟草试验站,利用289个表层土样,研究了16 m间距的栅格取样法(对照,253个土样,扣除36个验证样点)、34 m间距的栅格取样法(115个土样)和随机取样法(115个土样)3种取样方式下土壤质地的空间插值精度。3种土壤颗粒指标中粉粒占68.43%,砂粒含量最少,占12.68%,黏粒含量略高于砂粒。砂粒和黏粒具有中等强度的变异性,粉粒具弱变异性,且数据符合正态分布。地统计分析显示,在分析该区域土壤质地时,采用栅格取样方法应适当增大取样间距,而采用随机取样方法可适当缩小取样间距。交叉检验显示,土壤质地成分在3种取样方式下的插值精度均以对照最大,栅格取样次之,随机取样最小。综合考虑插值误差、样品采集和分析成本及时效性等因素,本研究建议在该区域进行土壤质地空间变异规律分析为生产服务时应采用随机取样。     

基于重叠分片法的仿人研抛螺旋线轨迹规划

提出一种重叠分片算法,它可产生C^1连续的轨迹规划偏置环,依此给出仿人研抛螺旋线轨迹规划。用普通算法（非人工智能）模拟了人工研抛轨迹,消除了除工件边界外的所有刀具轨迹转折和棱角,产生的准螺旋线轨迹适用于高速铣削和研抛。给出加工重复率的定义,评估了加工效率并分析了适用的分片密度。本算法只需调节权因子w1就可连续调节加工重复率。全部算法通过了Matlab的仿真验证。     

基于混合地理加权回归与克里格的区域降水量空间插值方法

基于四川省区域范围内144个气象站点的实测降水数据,在综合考虑空间位置、地形等影响因素的基础上,采用改进的回归克里格模型,即混合地理加权回归克里格模型（MGWRK）对四川省年降水量的空间分布进行空间插值,并与普通克里格（OK）、全局回归克里格（GRK）和地理加权回归克里格（GWRK）等模型的插值效果进行对比分析。结果表明：（1）应用逐步回归法筛选确定的用于回归分析的影响因子组合为经度、纬度和坡度,可有效消除解释变量间的多重共线性,为后续的空间插值奠定基础;（2）同一回归变量在地理加权回归（GWR）与全局回归（GR）两种回归模型中的AICc（修正的赤池信息量准则,Corrected Akaike Information Criterion）值之差（ΔAICc）可用于定量判定各回归变量的空间非平稳性类型,据此将变量坡度设为全局变量,经度和纬度设为局部变量进行处理。在此基础上,通过MGWRK模型对四川省年降水量进行空间插值;（3）MGWRK插值模型综合考虑了空间位置、地形等多个影响因素及其与降水相互关系的空间非平稳性特征,相对于传统的OK和GRK法具有更高的插值精度。     

兼顾冷却和降噪要求的后置客车冷却风扇优化设计

对一款后置客车风扇进行选配试验,取得了不同风扇性能参数及噪声水平。依据拟合与插值理论对原数据进行插值处理,获得了足够多的仿真数据,方便了对风扇的性能参数及噪声水平比较,并从中筛选出大风量、低噪声风扇,风扇装车测试结果表明,筛选出的风扇与原风扇相比在各项性能参数指标不下降的前提下,降低了噪声水平,同时改善噪声的频谱结构,为严格噪声法规下的风扇选取提供了一条有效途径。     

基于GIS的武汉市住宅地价空间分布分析

以武汉市中心城区为研究区,通过收集2008～2011年住宅地价交易资料,在ArcGIS9.3的支持下,采用空间插值分析,获取了住宅地价分布信息及等值线图,分析了住宅地价的空间分布。结果表明:武汉市中心城区住宅地价空间分布存在明显差异,高值区主要分布在市中心;住宅地价高值区与商业中心呈现较强的一致性。该结论反映了武汉市中心城区住宅地价的分布规律,为研究其他种类地价提供了参考价值。