Application of GIS and remote sensing techniques in frost risk mapping for mitigating agricultural losses in the Aberdare ecosystem,Kenya   总被引：1，自引：0，他引：1  

Susan Malaso Kotikot  Simon M. Onywere 《国际地球制图》2015,30(1):104-121

Frost is a perennial agricultural hazard that normally causes crop damage leading to huge agricultural losses within the Kenyan highlands; aggravated by inadequate information on frost. This research mapped frost hotspots within the Aberdare and Mount Kenya regions and identified the extent of arable land under frost risk while establishing the trend of minimum temperature occurrences between the years 2000 and 2013. Minimum temperature values were extracted from daily Moderate Resolution Imaging Spectroradiometer land surface temperature data-sets, and frost risk categorized into very severe frost (<250 K), severe frost (250–260 K), moderate frost (260–270 K), minor frost (270–280 K) and areas of no frost. Concentration of frost (<273 K) was mapped within regions above 1500 m asl and occasional occurrences within valleys lower than this altitude with recurrent occurrences in the months of April, May, July, August and November. Elevation, land surface convexity and humidity were found to influence frost occurrence. Improved agricultural practice to mitigate against losses is recommended.  相似文献   

A method for assessing kinematic bending moments at the pile head     

Luca de Sanctis  Rosa M. S. Maiorano  Stefano Aversa 《地震工程与结构动力学》2010,39(10):1133-1154

The conventional design methods for seismically loaded piles still concentrate in providing adequate resistance from the pile to withstand only the inertial bending moments generated from the oscillation of the superstructure, thus neglecting the effect of kinematic interaction between pile and soil. By contrast there has been extensive research on kinematic effects induced by earthquakes and a number of simplified methods are available for a preliminary evaluation of kinematic bending moments at the interface between two soil layers. Less attention has been paid to the effects of kinematic interaction at the pile‐head. The paper summarizes recent research work on kinematic response analysis of fixed‐head piles aimed at the performance evaluation of a piled foundation. Results from an extensive parametric study, undertaken by means of three‐dimensional FE analyses, suggest a new criterion to predict kinematic bending effects at the pile head, where the combination of kinematic and inertial effect may be critical. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

滑脱断层曲率在金矿成矿规律研究中的应用   总被引：2，自引：0，他引：2       下载免费PDF全文

周继彬  曾佐勋  樊春 《地质找矿论丛》2001,16(3):178-181

滑脱断层在金矿成矿过程中是一个重要的控矿因素。根据陕甘川邻接区的金矿分布位置与滑脱断层的关系，得出陕甘川邻接区中滑脱断层曲率大于4的密集区是金矿分布的远景位置。探讨了滑脱断层曲率与矿床分布的规律且分析了断层曲率的数学计算方法，并编制了自动追踪断层求曲率的软件，将它应用于陕甘川邻接区金矿预测中并获得成功。  相似文献   

A unified approach to ray bending, ray perturbation and paraxial ray theories     

Roel Snieder  Carl Spencer 《Geophysical Journal International》1993,115(2):456-470

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具有弯曲效应的层状结构岩体变形的Cosserat介质分析方法   总被引：13，自引：9，他引：13  

佘成学  熊文林 《岩土力学》1994,15(4):12-19

在反倾向层状岩体边坡、有底鼓现象的巷道以及隧洞工程中，岩体常出现弯曲变形及弯曲破坏现象。常规的等效连续介质理论忽略了梯度应力的影响，因而不能很好解决上述工程问题．Ｃｏｓｓｅｒａｔ介质理论以具有一定尺度的微元体为研究对象，引进了偶应力及弯曲曲率概念，从而考虑了弯曲效应对介质变形特性的影响。本文首先介绍Ｃｏｓｓｅｒａｔ介质理论的基本原理，然后建立有限元计算模式，最后通过算例，说明这种模式对计算具有弯曲效应的展状岩体变形问题是有效的。  相似文献   

fx-4800P型计算器钻孔内地质点定位程序     

杜荣学  邢福林  段泓娟 《地质找矿论丛》2005,20(Z1):196-198

文章探讨了用CASIO fx-4800P型可编程计算器根据钻孔弯曲度测量数据计算钻孔在任意标高(中段)位置和孔内过矿点、构造点等任意点的三维坐标的应用程序,在程序中设置了"程序语言"以避免运算中出现的失误,并介绍了程序的操作过程.  相似文献   

Application of fluid mechanic principles to the study of geodynamic processes at trench-arc-back arc systems     

Albert T. Hsui 《Pure and Applied Geophysics》1988,128(3-4):661-681

Geological processes at trench-arc-back arc systems are some of the most complex tectonic processes in need of study. A large amount of data based on geological and geophysical observations has been accumulated. To synthesize these data, mathematical models have proven to be very useful. Because geological processes are directly related to the dynamical behavior of the solid earth, many of them can be investigated in terms of fluid flow models. Some applications of fluid flow principles in studying tectonic processes at convergent plate boundaries are discussed in this paper. When mantle processes are modeled as convective systems, they are found to have direct implications for the determination of slab dip angles. Additionally, they can also account for the high heat flows in the back arc basins, provide a mechanism for back arc opening, and resolve the question whether subducted oceanic crust can reach melting at shallow depth for island arc magma generation. Besides mantle processes, flow models can also be used to study surface processes. A simple one-parameter plane flow theory is used to model the evolution of trench geometries. This model is able to fit simulataneously the trench curvature and the differential paleomagnetic rotation between volcanic islands for the Mariana. Despite the simplicity of many of these models, their ability to synthesize geological and geophysical data at convergent plate boundaries is quite remarkable.  相似文献   

幔汁(ACOHNS)流体的重大意义   总被引：24，自引：1，他引：24  

杜乐天 《大地构造与成矿学》1989,13(1):91-99

详细探讨了幔汁及幔汁活动对地壳中各种地质作用的重大影响,分析幔汁的成分结构,运动方式和对地质作用的控制。  相似文献   

Assessment of seismic performance of extended pile‐shafts     

Y. H. Chai  S. T. Song 《地震工程与结构动力学》2003,32(12):1937-1954

The seismic performance of extended pile‐shafts subjected to the current level of displacement ductility demand is assessed for different soil conditions. Local curvature ductility demand is compared with the curvature ductility capacity provided by the current level of confining steel. Parameters in the assessment of extended pile‐shafts include the undrained shear strength of cohesive soils, relative density of cohesionless soils, aboveground height, longitudinal reinforcement ratio, axial force level and pile diameter. Results indicate that the curvature ductility demand in the pile decreases with increased soil stiffness but increases with increased aboveground height. The curvature ductility demand however is not sensitive to the longitudinal reinforcement ratio or axial force level, and is independent of the pile diameter. Results further indicate that the curvature ductility capacity available from the current level of confining steel may not be adequate for tall extended pile‐shafts, especially for piles with large longitudinal reinforcement ratio and embedded in soft or loose soils. Limits on the maximum longitudinal reinforcement ratio are suggested in the paper. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Characterization and reconstruction of a rock fracture surface by geostatistics   总被引：1，自引：0，他引：1  

A. Marache  J. Riss  S. Gentier  J.‐P. Chils 《国际地质力学数值与分析法杂志》2002,26(9):873-896

It is well understood that, in studying the mechanical and hydromechanical behaviour of rock joints, their morphology must be taken into account. A geostatistical approach has been developed for characterizing the morphology of fracture surfaces at a decimetre scale. This allows the analysis of the spatial variability of elevations, and their first and second derivatives, with the intention of producing a model that gives a numerical three‐dimensional (3D) representation of the lower and upper surfaces of the fracture. Two samples (I and II) located close together were cored across a natural fracture. The experimental data are the elevations recorded along profiles (using recording steps of 0.5 and 0.02 mm, respectively, for the samples I and II). The goal of this study is to model the surface topography of sample I, so getting estimates for elevations at each node of a square grid whose mesh size will be, for mechanical purposes, no larger than the recording step. Since the fracture surface within the sample core is not strictly horizontal, geostatistical methods are applied to residuals of elevations of sample I. Further, since structural information is necessary at very low scale, theoretical models of variograms of elevations, first and second derivatives are fitted using data of both that sample I and sample II. The geostatistical reconstructions are computed using kriging and conditional simulation methods. In order to validate these reconstructions, variograms and distributions of experimental data are compared with variograms and distributions of the fitted data. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献