城市模型研究的发展趋势及展望

从内容、空间尺度、时间维、综合程度、建模方式、复杂程度和数学方法等方面对目前的城市模型进行了系统的分类。论述了城市模型研究的发展趋势：模型研究内容日益丰富和多元化;从静态模拟到动态模拟发展;从子系统模拟向综合系统模拟发展;遥感和GIS的应用以及与城市模型的集成。对城市模型研究的未来发展进行了展望,认为未来的城市模型开发应基于综合方法的思想,注重加强城市基本理论和多学科交叉研究,强调城市模拟的动态性和综合性。充分借助遥感与GIS等技术手段进行研究。     

Toward a more consistent evolution model for the local galactic disk

Infall models for the evolution of the local galactic disk were studied and confronted with a large number of observational constraints from the solar vicinity, inclusive of the white dwarf luminosity function. The models are characterized as follows: 1. The key-functions (SFR, IMF, gas infall rate) are not prescribed by simple laws, but are directly derived from observational constraints. 2. A scatter in the metallicity at fixed age is considered which partly reflects inhomogeous chemical evolution. 3. Special attention is drawn to the internal consistency of the models. 4. In addition to infall of low-metallicity gas, metal-enriched outflows are allowed. The “best” model is characterized by a disk age of ≈︁ 12 Gyr, a SFR which is decreasing over the first half and is nearly constant over the second half of the disk evolution, and by a similar temporal run of the gas infall rate. Moderate metal-enriched outflow can not be excluded.     

不同破坏准则下水合物沉积物的统计损伤模型

利用连续介质损伤力学理论与概率统计方法,假设水合物沉积物微元强度服从Weibull分布,在现有室内三轴和直剪试验数据的基础上,考虑水合物饱和度的影响,分别建立了基于修正Mohr-Coulomb强度准则和修正Lade-Duncan强度准则的水合物沉积物统计损伤本构模型,并将理论模型预测结果与室内试验进行对比,验证了模型的有效性。结果显示：基于Lade-Duncan强度准则的损伤本构模型能够较准确地反映水合物沉积物峰前的应力?应变规律,而基于修正Mohr-Coulomb强度准则的损伤本构模型则对于模拟峰后的应变软化特征有较好的适用性。对于在低有效围压、不同水合物饱和度条件下的水合物沉积物,基于修正Mohr-Coulomb强度准则的损伤本构模型的模拟精确性要优于基于修正Lade-Duncan准则的损伤模型;而在同一饱和度、不同有效围压条件下,基于修正Lade-Duncan强度准则的损伤本构模型的模拟结果则要优于基于修正Mohr-Coulomb强度准则的损伤本构模型。     

地球磁层的磁场模型

1958年卫星探测发现了磁层,至今已有半个世纪,对磁层电场、电流体系、磁场、粒子分布和等离子体波的探测研究构成了空间物理的重要内容,其结果是各种磁层模型的出现.本文简要综述磁层磁场建模的基本原理、方法和发展历史,对十几种重要的磁层模型的特点、局限性和适用范围进行了对比分析,以Tyganenko模型为例,讨论了磁层模型发展的趋势.     

Estimation of daily space–time precipitation series for macroscale hydrological modelling

An important problem in modelling macroscale basins, especially for sparsely observed regions, is the lack of precipitation information. Alternatives to using straightforward interpolated surface observations include the utilization of more advanced interpolation techniques and the use of additional precipitation information from atmospheric models. Conventional and geostatistical methods are applied for optimal interpolation and assimilation of observed and model precipitation. Various time-series of daily areal precipitation distributions are produced and compared using not only an internal precipitation validation, but also an objective verification based on stream flow simulations. The Mackenzie River Basin in north-western Canada is used as the study area and hydrological simulations are carried out with the model SLURP. It was found that better interpolation techniques and the use of combined precipitation data can improve the hydrological simulations and that the enhancements are related to the relative size of the simulation units used. © 1998 John Wiley & Sons, Ltd.     

地下水数值模拟不确定性分析研究进展

地下水数值模拟不确定性分析旨在提高研究区域地下水流的模拟精度。学者们将地下水数值模拟不确定性分析分为:模型的不确定性、参数的不确定性以及资料的不确定性三类,其中参数的不确定性分析在研究中是最为重要的。同时,对模型、参数、资料不确定性分析的研究进展和成果进行归纳总结,补充关于参数不确定性分析过程中的替代模型的一些研究成果以及模型不确定性分析的多模型分析;强调在地下水数值模拟的过程中,重视模型、资料的不确定性分析;展望未来,随着地下水数值模拟不确定性分析研究的深入,方法和应用会更加多样化。     

Estimating tree canopy cover using harmonic regression coefficients derived from multitemporal Landsat data

The goal of this study was to evaluate whether harmonic regression coefficients derived using all available cloud-free observations in a given Landsat pixel for a three-year period can be used to estimate tree canopy cover (TCC), and whether models developed using harmonic regression coefficients as predictor variables are better than models developed using median composite predictor variables, the previous operational standard for the National Land Cover Database (NLCD). The two study areas in the conterminous USA were as follows: West (Oregon), bounded by Landsat Worldwide Reference System 2 (WRS-2) paths/rows 43/30, 44/30, and 45/30; and South (Georgia/South Carolina), bounded by WRS-2 paths/rows 16/37, 17/37, and 18/37. Plot-specific tree canopy cover (the response variable) was collected by experienced interpreters using a dot grid overlaid on 1 m spatial resolution National Agricultural Imagery Program (NAIP) images at two different times per region, circa 2010 and circa 2014. Random forest model comparisons (using 500 independent model runs for each comparison) revealed the following (1) harmonic regression coefficients (one harmonic) are better predictors for every time/region of TCC than median composite focal means and standard deviations (across times/regions, mean increase in pseudo R² of 6.7% and mean decrease in RMSE of 1.7% TCC) and (2) harmonic regression coefficients (one harmonic, from NDVI, SWIR1, and SWIR2), when added to the full suite of median composite and terrain variables used for the NLCD 2011 product, improve the quality of TCC models for every time/region (mean increase in pseudo R² of 3.6% and mean decrease in RMSE of 1.0% TCC). The harmonic regression NDVI constant was always one of the top four most important predictors across times/regions, and is more correlated with TCC than the NDVI median composite focal mean. Eigen analysis revealed that there is little to no additional information in the full suite of predictor variables (47 bands) when compared to the harmonic regression coefficients alone (using NDVI, SWIR1, and SWIR2; 9 bands), a finding echoed by both model fit statistics and the resulting maps. We conclude that harmonic regression coefficients derived from Landsat (or, by extension, other comparable earth resource satellite data) can be used to map TCC, either alone or in combination with other TCC-related variables.     

基于Argo实测流场数据对5套海洋模式产品中赤道太平洋中层流的评估

本文以Argo轨迹资料计算的赤道太平洋中层流(1 000 m深度流场)作为实测数据,从空间结构特征和时间变化特征两方面对5套常用海洋模式产品(OFES、LICOM、HYCOM、ECCO2和SODA)进行了评估。Argo流场显示赤道太平洋中层流呈条带状结构,且存在明显的西强东弱和南强北弱特征。此外,赤道太平洋中层流存在明显的季节变化且其相位关于赤道对称。5套模式产品的评估结果表明,SODA流场与实测流场最接近,其时空变化特征都与实测流场基本一致;其次是ECCO2流场,除流场动能偏小以外,其他各方面都与实测流场一致;OFES、LICOM和HYCOM流场的模拟效果较差,但都能再现条带状结构特征。