城市“屋顶农业”开发的适宜性试验—以柑桔栽培为例   总被引：1，自引：0，他引：1  

骆高远  胡云好 《热带地理》1995,15(2):115-119

本文通过对屋顶栽培柑桔的对比试验和分析，认为通过开发“屋顶农业”来绿化城市屋面，不仅具有生态效益，而且具有社会效益和经济效益。值得推广。  相似文献   

Geomechanical evaluation of a coal mine arched entry     

J. R. Aggson  D. P. Mouyard 《Geotechnical and Geological Engineering》1988,6(3):185-193

Summary In an effort to minimize cutter roof failures in longwall development entries of a West Virginia coal mine, a three-entry system was developed with the center entry arched into the strata above the coal seam. The purpose of the arched entry was to modify the horizontal stress envelope associated with the three-entry system and improve roof conditions in the adjacent outside entries.Contrary to the predictions of elastic analyses, the presence of the arched entry improved roof conditions by eliminating cutter roof failures in the outside entries.In situ stress determinations and numerical modeling techniques were employed to quantify the impact of the arch and investigate the mechanism of stress relief associated with the arched entry. Stress determinations and underground observations indicated that the roofs of the outside entries were within the zone of stress relief generated by the arch, and that failure or movement along bedding plane discontinuities played a major role in the formation of the stress relieved zone. The numerical model incorporated horizontal joints to simulate bedding plane discontinuities. The properties of the joints were adjusted until roof stresses predicted by the model were in agreement with measured stress profiles. This process resulted in a calibrated analytical tool that could be used to evaluate alternate mining geometries.  相似文献   

高瓦斯面顶板走向钻孔抽放数值模拟与试验     

邓明  张国枢  刘泽功  秦汝祥 《煤田地质与勘探》2008,36(5)

高瓦斯矿井"U"型通风工作面采空区上隅角容易积聚瓦斯。以渗流理论为基础,根据气体扩散定律和质量守恒定律,建立了顶板走向钻孔抽放采空区瓦斯流场数学模型,并用6点隐式有限差分法进行了求解。以VB6.0为平台,利用工程软件SURFER模拟了抽放钻孔周围瓦斯压力场,并在现场进行了工业试验。理论研究与现场实践均表明:顶板走向钻孔抽放采空区瓦斯是解决高瓦斯工作面上隅角瓦斯积聚的一种行之有效的措施;顶板裂隙程度和状态是影响瓦斯抽放量的主要因素,将钻孔布置在适当的裂隙带中,瓦斯抽放浓度可达30%～90%,抽放负压可达50～55 kPa;数值模拟方法研究采空区瓦斯运移等工程实际问题是可行的。  相似文献   

3D building roof reconstruction from airborne LiDAR point clouds: a framework based on a spatial database   总被引：1，自引：0，他引：1  

Rujun Cao  Xinyi Liu  Zongze Zhao 《International journal of geographical information science》2017,31(7):1359-1380

Three-dimensional (3D) building models are essential for 3D Geographic Information Systems and play an important role in various urban management applications. Although several light detection and ranging (LiDAR) data-based reconstruction approaches have made significant advances toward the fully automatic generation of 3D building models, the process is still tedious and time-consuming, especially for massive point clouds. This paper introduces a new framework that utilizes a spatial database to achieve high performance via parallel computation for fully automatic 3D building roof reconstruction from airborne LiDAR data. The framework integrates data-driven and model-driven methods to produce building roof models of the primary structure with detailed features. The framework is composed of five major components: (1) a density-based clustering algorithm to segment individual buildings, (2) an improved boundary-tracing algorithm, (3) a hybrid method for segmenting planar patches that selects seed points in parameter space and grows the regions in spatial space, (4) a boundary regularization approach that considers outliers and (5) a method for reconstructing the topological and geometrical information of building roofs using the intersections of planar patches. The entire process is based on a spatial database, which has the following advantages: (a) managing and querying data efficiently, especially for millions of LiDAR points, (b) utilizing the spatial analysis functions provided by the system, reducing tedious and time-consuming computation, and (c) using parallel computing while reconstructing 3D building roof models, improving performance.  相似文献   

Maize seed choice and perceptions of climate variability among smallholder farmers     

《Global Environmental Change》2017

Despite decades of research and interventions, crop yields for smallholder farmers across sub-Saharan Africa are dramatically lower than in developed countries. Attempts to address low yields of staple crops in Africa since the Green Revolution through policies and investments in advanced seed cultivars have had mixed results. Numerous countries have heartily embraced and promoted hybrid cultivars through government subsidy programs and investments in research and seed multiplication. One possible explanation for why these programs have not resulted in more significant yield improvements is the challenge faced by farmers to select cultivars that are suited to their local environmental conditions. The question of what seeds farmers choose is exceptionally complex as it is often affected by local seed availability, the availability of information on seed performance, and the transfer of that information to farmers. At the foundation of this choice are farmers’ perceptions of different seed varieties coupled with their perceptions of climate variability. We examine seed choice in Zambia, a country with decades of hybrid maize seed development and supporting policies. We demonstrate how input subsidy programs and seed market liberalization have led to choice overload and a discontinuity in information exchange between farmers and seed companies. The decision making environment is further complicated by the heterogeneity in growing conditions and its variable impact on seed performance, which complicates characterization of seed duration at the farm level. Perceptions and biases related to climate variability effect seed choice, and potentially lead farmers to make risk averse decisions, which ultimately depress maize yields.  相似文献   

Enhanced land use/cover classification of heterogeneous tropical landscapes using support vector machines and textural homogeneity     

《International Journal of Applied Earth Observation and Geoinformation》2013

Land use/cover classification is a key research field in remote sensing and land change science as thematic maps derived from remotely sensed data have become the basis for analyzing many socio-ecological issues. However, land use/cover classification remains a difficult task and it is especially challenging in heterogeneous tropical landscapes where nonetheless such maps are of great importance. The present study aims at establishing an efficient classification approach to accurately map all broad land use/cover classes in a large, heterogeneous tropical area, as a basis for further studies (e.g., land use/cover change, deforestation and forest degradation). Specifically, we first compare the performance of parametric (maximum likelihood), non-parametric (k-nearest neighbor and four different support vector machines – SVM), and hybrid (unsupervised–supervised) classifiers, using hard and soft (fuzzy) accuracy assessments. We then assess, using the maximum likelihood algorithm, what textural indices from the gray-level co-occurrence matrix lead to greater classification improvements at the spatial resolution of Landsat imagery (30 m), and rank them accordingly. Finally, we use the textural index that provides the most accurate classification results to evaluate whether its usefulness varies significantly with the classifier used. We classified imagery corresponding to dry and wet seasons and found that SVM classifiers outperformed all the rest. We also found that the use of some textural indices, but particularly homogeneity and entropy, can significantly improve classifications. We focused on the use of the homogeneity index, which has so far been neglected in land use/cover classification efforts, and found that this index along with reflectance bands significantly increased the overall accuracy of all the classifiers, but particularly of SVM. We observed that improvements in producer's and user's accuracies through the inclusion of homogeneity were different depending on land use/cover classes. Early-growth/degraded forests, pastures, grasslands and savanna were the classes most improved, especially with the SVM radial basis function and SVM sigmoid classifiers, though with both classifiers all land use/cover classes were mapped with producer's and user's accuracies of ∼90%. Our classification approach seems very well suited to accurately map land use/cover of heterogeneous landscapes, thus having great potential to contribute to climate change mitigation schemes, conservation initiatives, and the design of management plans and rural development policies.  相似文献   

多参数岩性地震反演在识别煤层顶板砂岩中的应用——以新景煤矿为例     

彭刘亚  崔若飞  任川 《地球物理学进展》2013,28(4)

山西国阳新能股份有限公司新景煤矿3煤层在掘进和回采过程中,频发煤与瓦斯突出事故,给煤矿安全生产带来隐患.通过多个采区的瓦斯地质调查,发现大部分区域的瓦斯突出与煤层的顶板岩性(砂岩)和煤层结构(煤层的冲刷变薄)密切相关,当3煤层被顶板砂岩冲刷变薄,即3煤层顶板砂岩的厚度增加时,极易发生瓦斯突出.本文对研究区的测井曲线进行特征分析,并对测井曲线进行融合处理,利用多参数岩性反演的方法获得的波阻抗数据体可以对3煤层顶板砂岩的分布特征进行详细研究.反演结果与实际情况吻合度较高,且在瓦斯突出点位置,煤层顶板的波阻抗值明显增大,并能够清晰地辨别砂岩的位置和空间形态,其研究成果对新景煤矿瓦斯预测和治理具有重要意义.  相似文献   

Book reviews     

David Fairbairn 《International journal of geographical information science》2013,27(1):53-64

A digital elevation model (DEM), which is used to represent a terrain surface, is normally constructed by applying an interpolation method on given sample elevation points. Interpolation methods can be classified into two classes: linear methods, which have a low time cost and are suitable for terrains where there is little change in elevation, and nonlinear methods, which normally consume comparatively more time and are more suitable for terrains where there are frequent changes in elevation. A hybrid interpolation method, which involves both a linear method and a nonlinear method of interpolation, is proposed in this paper. The proposed method aims to integrate the advantages of both linear and nonlinear interpolation methods for the refinement of regular grid DEM. Here, the bilinear is identified as the linear method, and the bi‐cubic is taken to be the nonlinear interpolation method. The hybrid method is an integration of a linear model and nonlinear interpolation model with a parameter that defines the weights for each of the models. The parameter is dependent on the complexity of the terrain, for which a DEM is to be interpolated. The experimental results in this study demonstrate that the hybrid method is effective for interpolating DEMs for various types of terrain.  相似文献   

Dominant simple-shear deformation during peak metamorphism for the lower portion of the Greater Himalayan Sequence in West Nepal: New implications for hybrid channel flow-type mechanisms in the Dolpo region     

《Journal of Structural Geology》2015

I conducted new vorticity and deformation temperatures studies to test competing models of the exhumation of the mid-crustal rocks exposed in the Dolpo region (West Nepal). My results indicate that the Main Central Thrust is located ∼5 km structurally below the previous mapped locations. Deformation temperature increasing up structural section from ∼450 °C to ∼650 °C and overlap with peak metamorphic temperature indicating that penetrative shearing was responsible for the exhumation of the GHS occurred at “close” to peak metamorphic conditions. I interpreted the telescoping and the inversion of the paleo-isotherms at the base of the GHS as produced mainly by a sub-simple shearing (Wm = 0.88–1) pervasively distributed through the lower portion of the GHS. My results are consistent with hybrid channel flow-type models where the boundary between lower and upper portions of the GHS, broadly corresponding to the tectonometamorphic discontinuity recently documented in west Nepal, represents the limit between buried material, affected by dominant simple shearing, and exhumed material affected by a general flow dominates by pure shearing. This interpretation is consistent with the recent models suggesting the simultaneous operation of channel flow- and critical wedge-type processes at different structural depth.  相似文献   

集合变分混合同化背景误差协方差流依赖性分析   总被引：4，自引：2，他引：2  

张明阳  张立凤  张斌  张晓慧 《气象科学》2015,35(6):728-736

通过单点观测试验的方法,对集合变分混合同化背景误差协方差的流依赖特征、流依赖性影响因子、产生原因,以及集合预报方法对流依赖性的影响进行了研究。结果表明:由于引入了集合信息,集合变分混合同化的分析增量与天气系统的分布有关,具有非均匀、各向异性的特征;这种流依赖特征对混合系数敏感,当集合协方差所占权重很小时,分析增量仍呈现出均匀、各向同性特征;混合同化背景误差协方差的流依赖特征不仅与集合样本有关,还与构造集合协方差的ETKF方法有关,只引入与环流形势密切相关的集合样本并不能使分析增量表现出显著的流依赖性,集合样本和ETKF方法共同作用才能将流依赖信息引入到混合协方差中,使分析增量出现流依赖特征;不同集合预报方法对混合协方差的流依赖特征有显著影响,考虑初值和物理过程的超级集合,以及在超级集合样本上再进行ETKF更新扰动后样本构造的混合协方差流依赖特征更加显著。  相似文献