Landmark‐based summarized messages for flood warning

In order to evacuate residents in time, flood warning systems must have rapid data processing algorithms to translate detailed numerical data into simple warnings and navigation aids. Although it is common to display warning messages by directly drawing red circles on a map embedded in a Web page to indicate the regions about to be inundated, such an approach has some drawbacks. We propose an alternative way by summarizing the warning messages based on landmarks, so that the messages can be short and convey even more information. We have designed two approaches to output such messages. They are the nearest landmark approach and the threshold approach, which differ in the way of determining which landmarks will be influenced by a certain flooded region. These two methods are implemented and we compare their performance through real and synthetic datasets. Experimental results show that the threshold approach usually takes less execution time than the nearest landmark approach. Its severity ranking of landmarks is also better suited to human behaviour.     

Research Note—Vegetation Effects on Suburban Air Conditioning

Conventional wisdom indicates that shade trees reduce air-conditioning energy demands in U.S. southern-tier states. Existing studies of shade effects on dwellings generally do not consider that contemporary home structures are inhabited and well insulated. Through a statistical analysis of weather, vegetative, and energy consumption data for 38 inhabited, modern homes in the eastern suburbs of Atlanta, we establish that existing tree plantings play only a small role in energy conservation for individual homes vis-à-vis insulation and heat gain from external walls and windows.     

Spatial autocorrelation of West Nile virus vector mosquito abundance in a seasonally wet suburban environment

The objective of this study is to quantify and model spatial dependence in mosquito vector populations and develop predictions for unsampled locations using geostatistics. Mosquito control program trap sites are often located too far apart to detect spatial dependence but the results show that integration of spatial data over time for Cx. pipiens-restuans and according to meteorological conditions for Ae. vexans enables spatial analysis of sparse sample data. This study shows that mosquito abundance is spatially correlated and that spatial dependence differs between Cx. pipiens-restuans and Ae. vexans mosquitoes.      

Integrating TM and ancillary geographical data with classification trees for land cover classification of marsh area

The main objective of this research is to determine the capacity of land cover classification combining spectral and textural features of Landsat TM imagery with ancillary geographical data in wetlands of the Sanjiang Plain, Heilongjiang Province, China. Semi-variograms and Z-test value were calculated to assess the separability of grey-level co-occurrence texture measures to maximize the difference between land cover types. The degree of spatial autocorrelation showed that window sizes of 3×3 pixels and 11×11 pixels were most appropriate for Landsat TM image texture calculations. The texture analysis showed that co-occurrence entropy, dissimilarity, and variance texture measures, derived from the Landsat TM spectrum bands and vegetation indices provided the most significant statistical differentiation between land cover types. Subsequently, a Classification and Regression Tree (CART) algorithm was applied to three different combinations of predictors: 1) TM imagery alone (TM-only); 2) TM imagery plus image texture (TM+TXT model); and 3) all predictors including TM imagery, image texture and additional ancillary GIS information (TM+TXT+GIS model). Compared with traditional Maximum Likelihood Classification (MLC) supervised classification, three classification trees predictive models reduced the overall error rate significantly. Image texture measures and ancillary geographical variables depressed the speckle noise effectively and reduced classification error rate of marsh obviously. For classification trees model making use of all available predictors, omission error rate was 12.90% and commission error rate was 10.99% for marsh. The developed method is portable, relatively easy to implement and should be applicable in other settings and over larger extents.     

柴达木盆地大柴旦盐湖区盐生植物根-土复合体力学强度试验研究

本文以柴达木盆地大柴旦盐湖区作为试验区,分别筛选出5种优势盐生植物,即海韭菜(Triglochin maritimum Linn.)、芦苇(Phragmites australis Trin.)、赖草(Leymus secalinus Tzvel.)、毛穗赖草(Leymus paboanus Claus.)、无脉苔草(Carex enervis C. A. Mey.)作为试验供试种,分别对5种盐生植物根-土复合体试样和不含根系素土试样进行了室内直接剪切试验和三轴压缩试验,对比了不含根系素土试样与根-土复合体试样的抗剪强度指标;在此基础上,评价了5种盐生植物根系增强土体抗剪强度作用。试验结果表明：(1)当含水量和密度值分别为29.01%和1.65g/cm3时,5种盐生植物根-土复合体试样的抗剪强度指标粘聚力c值为10.38kPa-19.19kPa,且显著大于素土试样的粘聚力c值5.95kPa,内摩擦角 值未表现出变化规律;(2)相对于不含根系的素土试样,由直剪试验和三轴试验得到的5种盐生植物根-土复合体试样的粘聚力增长幅度分别为16.8%~108.7%、19.2%~113.6%;(3)由直剪试验与三轴试验结果表明,区内5种盐生植物根-土复合体试样抗剪强度大小变化顺序表现出一致的规律性,即由大至小依次为：芦苇、海韭菜、赖草、毛穗赖草、无脉苔草、素土。该项研究结果为区内进一步开展盐生植物增强土体抗剪强度机理等方面的研究具有理论研究价值和实际指导意义。     

利用三维激光扫描技术进行涉案伐倒木材积测定

利用三维激光扫描系统,获得伐倒木的整体点云数据,利用点云应用微积填充的方式计算出伐倒木的材积,将计算结果与根据伐倒木求积式计算出的材积结果进行比较。结果表明,激光扫描仪测得的伐倒木材积数据精度、测量效率均比较高,可以满足林业调查精度的要求,为快速、高效地测定涉案伐倒木材积提供了技术支持。     

我国南方强潮海岸红树植物对潮流的调制作用

至今,关于红树植物对潮流的调制作用的研究非常有限,尤其是红树植物对垂向流速剖面的影响还不清楚。本研究利用自主研发的自动升降架于大潮期间对浙江南部乐清湾西门岛秋茄种植区的红树林滩进行垂向多点观测。结果表明,在所研究的红树林内,整个垂向剖面的流速普遍较低。树干和冠层引起的拖曳力在垂向上的增加,使得红树林内垂向流速剖面呈现"流速随距底高度增大而减小"的规律。此外,湍流能量密度在垂向上也呈现出与红树植物垂向结构相对应的变化。与光滩（半对数）和盐沼（近"J"形）内流速的垂向结构相比,红树植物以一种不同的方式对垂向流速剖面产生重要影响。     

Longitudinal dynamic impedance of a static drill rooted nodular pile embedded in layered soil

The static drill rooted nodular (SDRN) pile is a new type of precast pipe pile with equally spaced nodes distributed along the shaft and wrapped by the surrounding cemented soil. In this paper, the longitudinal dynamic response of the SDRN pile embedded in layered soil is investigated with respect to the complexity of the pile body structure and the pile–soil contact condition. First, the shear complex stiffness transfer model is used to simulate the radial inhomogeneity of the surrounding soil. Then, the governing Equations of the pile–soil system subjected to longitudinal dynamic loading are established. The analytical solution for the dynamic response at the pile head is obtained by the shear complex stiffness transfer method and the impedance function transfer method. The degenerate case of the present solution is compared with the published solution to verify its reliability, and the complex impedance of the SDRN pile is compared with that of the precast pipe pile and the bored pile. Finally, a parametric study is conducted to investigate the influence of pile–soil parameters on the complex impedance at the pile head within the low frequency range concerned in the design of the dynamic foundation.     

Topsoil morphology indicates bio-effective redox conditions in Venice salt marshes

Visual traces of iron reduction and oxidation are linked to the redox status of soils and have been used to characterise the quality of agricultural soils. We tested whether this feature could also be used to explain the spatial pattern of the natural vegetation of tidal habitats. If so, an easy assessment of the effect of rising sea level on tidal ecosystems would be possible. Our study was conducted at the salt marshes of the northern lagoon of Venice, which are strongly threatened by erosion and rising sea level and are part of the world heritage “Venice and its lagoon”. We analysed the abundance of plant species at 255 sampling points along a land–sea gradient. In addition, we surveyed the redox morphology (presence/absence of red iron oxide mottles in the greyish topsoil horizons) of the soils and the presence of disturbances. We used indicator species analysis, correlation trees and multivariate regression trees to analyse relations between soil properties and plant species distribution. Plant species with known sensitivity to anaerobic conditions (e.g. Halimione portulacoides) were identified as indicators for oxic soils (showing iron oxide mottles within a greyish soil matrix). Plant species that tolerate a low redox potential (e.g. Spartina maritima) were identified as indicators for anoxic soils (greyish matrix without oxide mottles). Correlation trees and multivariate regression trees indicate the dominant role of the redox morphology of the soils in plant species distribution. In addition, the distance from the mainland and the presence of disturbances were identified as tree-splitting variables. The small-scale variation of oxygen availability plays a key role for the biodiversity of salt marsh ecosystems. Our results suggest that the redox morphology of salt marsh soils indicates the plant availability of oxygen. Thus, the consideration of this indicator may enable an understanding of the heterogeneity of biological processes in oxygen-limited systems and may be a sensitive and easy-to-use tool to assess human impacts on salt marsh ecosystems.