Local food sovereignty for global food security? Highlighting interplay challenges     

《Geoforum》2017

The food sovereignty movement proposes a localist approach to meeting food security while delivering broader social, economic and environmental benefits. The movement is spawning multiple local projects of food sovereignty, whereby people are empowered to define their own culturally and environmentally appropriate food systems. As the number of enacted examples increases, the movement is also affecting change at national (and international) levels, with a number of countries creating national strategies or legislation for food sovereignty. We reflect on the challenges created by such scaling up within the existing food system. We propose a focus on issues of institutional interplay in order to identify and critique challenges. We highlight three interplay situations between multiple, diverse enactments of food sovereignty at multiple levels, and between food sovereignty and the broader institutional contexts within which they are embedded.  相似文献   

云南地区中小地震静力学和动力学参数定标关系   总被引：1，自引：0，他引：1  

刘丽芳  杨晶琼  华卫  苏有锦  刘杰 《中国地震》2011,27(3):268-279

通过消除S波观测谱中的传播路径、场地响应、仪器响应等影响因素,得到中小地震的震源谱.根据Brune震源模型,运用遗传算法计算了地震矩、应力降、震源半径等震源参数;通过考虑由于有限的仪器带宽带来的地震辐射能量低估及补偿问题,测定了中小地震辐射能量;分析了云南地区ML2.0 ～5.3地震静力学和动力学参数定标关系.结果表明:地震矩为2.1×1012～1.2 ×1016N·m,地震矩M0和震级ML的线性关系式为lgM0=1.01ML+10.59;震源破裂半径在86.9～1220.4m之间,地震矩M0与震源半径a之间的关系式为lgM0 =0.003a+ 12.90;应力降结果介于0.03 ～57.55MPa之间,当M0＜4×1014N.m时,应力降随地震矩的增大而增大,当M0≥4 ×1014N·m时,应力降与地震矩之间无明显的依赖关系;地震矩M0与拐角频率∫c明显有依赖关系,二者之间的关系式为lgfc=- lgM0+5.32;地震辐射能量ER在3.01×106～2.06×1012J之间,地震辐射能量ER与震级ML之间的关系为lgER=1.18ML+5.69.当M0＜4×1014N·m时,折合能量有随地震矩增大而增大的趋势,当M0≥4×1014N·m时,折合能量不随地震矩的增大而变化;地震视应力范围为0.02～31.4MPa之间,视应力与震源深度之间没有明显的依赖性.  相似文献   

Scaling of fault attributes: A review   总被引：3，自引：0，他引：3  

Anita Torabi  Silje Støren Berg 《Marine and Petroleum Geology》2011,28(8):1444-1460

The present paper reviews our current understanding of fault dimensions and their scaling laws, with special focus on faults in siliciclastic rocks. The aim is to provide a comprehensive overview of recent research in order to identify strengths and challenges related to the way this topic is being addressed. We here investigate the statistical distributions of different fault attributes, e.g. fault length, displacement, damage zone width, core thickness at different scales and tectonic regimes. Biases related to sampling (resolution effect) and statistical visualization of data are discussed. The interrelationship between different faults attributes is addressed, e.g. fault displacement versus length, and fault core thickness and fault damage zone width. The results of this study show that global statistical relationships for fault attribute populations may not be valid, since the fault attributes at different scales behave differently and the compiled data on fault displacement-length exhibit breaks in the transition between faults at different scales, i.e. from small to medium scale faults at ∼1 m displacement and from medium to large scale faults at ∼1000 m displacement. This may also be the case for fault displacement-core thickness and fault displacement-damage zone width, as slight variation in the relationship can be observed between attribute populations derived from small- and medium-size faults at ∼1 m displacement. These differences may indicate the existence of characteristic length scales in fault populations, which could imply a hierarchical ordering of fault systems. The majority of data in our compiled database show no clear distinction between rocks from different lithologies and tectonic settings. Finally, the mechanical aspects of the processes of faulting with respect to the scaling relationships are discussed. Conceptual diagrams for the evolutionary processes of faulting at different scales based on the observed relationships on the plotted datasets of faults’ main attributes (fault displacement, length, core thickness and damage zone width) are proposed.  相似文献   

地理空间数据的尺度转换   总被引：3，自引：0，他引：3  

胡云锋  徐芝英  刘越  艳燕 《地球科学进展》2013,28(3):297-304

尺度一般是指空间范围的大小,地理空间数据的尺度转换是尺度研究的重要问题之一。针对地理信息系统(GIS)技术支持下的地理空间数据尺度转换问题,首先回顾了尺度转换的理论基础,即等级理论、分形理论、区域化随机变量理论、地理学第一定律等理论的基本内涵;然后总结了地理学不同研究领域内主要的尺度转换方法,重点分析了重采样法、变异函数法、分形分维法及小波分析法的基本原理、模型方法与典型应用案例;最后介绍了地理空间数据尺度转换效应研究的进展。基于上述总结和分析认为:构建一套无级变换的、系统的尺度转换方法,整合不同学科领域的数据与过程模型、形成数据模型同化的技术体系,这是地理空间数据尺度转换研究的重要课题。  相似文献   

Threshold for initiation of motion of unimodal and bimodal sediments     

Shaileshkumar B.PATEL  Prem Lal PATEL  Prakash Devidas POREY 《国际泥沙研究》2013,28(1):24-33

Experimental data,obtained from previous studies,on Critical Tractive Stress(CTS) of non-uniform sediments, have been used to verify the adequacy of existing relationships for CTS of non-uniform bimodal sediments.Keeping in view the performance of such relationships,a new relationship for computation of dimensionless CTS of individual size fraction of non-uniform unimodal and bimodal sediments has been proposed in the form of power law.The coefficient and exponent of the proposed power law have been empirically correlated with sediment characteristics for available sediment data.The proposed relationship has been validated with independent flume and field data to assess their applicability for unimodal and bimodal sediments.  相似文献   

1/f Fluctuations in geoelectrical signals observed in a seismic area of Southern Italy     

Marianna Balasco  Vincenzo Lapenna  Luciano Telesca   《Tectonophysics》2002,347(4)

Recent studies have shown that many natural systems display temporal fluctuations with long-range power-law correlations, suggesting a fractal geometry of the underlying dynamical system. Four geoelectrical time series, measured in a seismic area of Southern Italy, are investigated by means of spectral tools in order to evidence the existence of power-law correlations. Results show the scaling behaviour for all the signals recorded, pointing to the presence of fractal features expressing a long-term correlation with scaling exponents which indicate stabilizing mechanisms. Furthermore, our findings suggest an observational evidence of correlations between the variation of parameters describing the temporal fluctuations of geoelectrical signals and earthquakes that occurred in the area investigated.  相似文献   

EFFECTS OF SPATIAL VARIABILITY ON THE SCALING OF LAND SURFACE PARAMETERIZATIONS   总被引：1，自引：0，他引：1  

ZHENGLIN HU  SHAFIQUL ISLAM 《Boundary-Layer Meteorology》1997,83(3):441-461

Understanding and modelling physical and dynamical processes over heterogeneous land surfaces have becomea central focus of many recent studies. There is aconsiderable debate, however, over how to representthe effects of spatial heterogeneity in mesoscale andglobal scale models. Here, a computationally efficientanalytical approach is presented to evaluate scalingproperties of land surface representations. It isshown that the effects of spatial variability may not benegligible for commonly encountered land surfaces andassociated parameterizations. Second-order correction termsinvolving variances of the parameters and covariancesof each pair of land surface parameters are developedto account for the effects ofheterogeneity. Using this analytical approach, weshow that the detail of spatial heterogeneity may not beimportant for the infrared radiation and reflectedsolar radiation from the surface, while sensible andlatent heat fluxes are shown to be sensitive toheterogeneity. Assumptions related todifferent parameterizations for the same physicalprocess could potentially lead to different inferencesregarding the influence of spatial heterogeneity. Theproposed approach, however, is capable of identifying therole of different parameterizations in estimating theinfluence of spatial heterogeneity. These analyticalresults are consistent with the results of severalrecent numerical and field experiments that deal withthe effects of small-scale heterogeneity in landsurface characteristics.  相似文献   

Sea-breeze scaling from numerical model simulations,Part I: Pure sea breezes     

Aurore Porson  Douw G. Steyn  Guy Schayes 《Boundary-Layer Meteorology》2007,122(1):17-29

Numerical model simulations of sea-breeze circulations under idealized conditions are subjected to dimensional analyses in order to resolve sea-breeze dynamical relations and unify previous results based on observations. The analysis is motivated by the fact that sea-breeze depth scaling and volume flux scaling are only partially understood. The analysis is based on nonlinear numerical modelling simulations in combination with recent observational scaling analyses. The analysis confirms scaling laws for sea-breeze strength dependence on governing variables and shows how the sea-breeze speed scale is controlled by surface heat flux. It also shows that the sea-breeze depth scale is controlled by stability. By combining sea-breeze speed and depth scales, the sea-breeze volume flux scale is determined by an equilibrium between the accumulated convergence of heat over land since sunrise and stable air advection from the sea surface.  相似文献   

Impact of different regression frameworks on the estimation of the scaling properties of radar rainfall   总被引：1，自引：0，他引：1  

Gabriele Villarini  Joseph B. Lang  Federico Lombardo  Francesco Napolitano  Fabio Russo  Witold F. Krajewski 《Atmospheric Research》2007,86(3-4):340-349

Rainfall is characterized by high variability both in space and time. Despite continuous technological progress, the available instruments that are used to measure rainfall across several spatio-temporal scales remain inaccurate. To remedy this situation, scaling relationships of spatial rainfall offer the potential to link the observed or predicted precipitation quantities at one scale to those of interest at other scales. This paper focuses on the estimation of the spatial rainfall scaling functions. Standard scaling analysis constructed by means of the ordinary least squares method often violates such basic assumptions implicit in its use and interpretation as homoschedasticity, independence, and normality of the errors. Consequently, the authors consider alternative regression frameworks i.e. bootstrapping regression, semi parametric linear model, and multilevel normal linear model to show how these different approaches exert a significant impact on the multifractal analysis of radar rainfall. In addition, the uncertainties associated with the construction of the scaling function due solely to the regression procedure are quantified. The radar data come from the polarimetric C-band weather radar located in Rome, Italy, and the scaling properties are computed for a square domain centred on the radar site with a side length of 128 km and a finest resolution of 1 km².  相似文献   

Comparison of relative permeability–fluid saturation–capillary pressure relations in the modelling of non-aqueous phase liquid infiltration in variably saturated,layered media     

F. Fritjof Fagerlund  Auli NiemiMagnus Odén 《Advances in water resources》2006

The characteristic functions relating relative permeabilities and capillary pressures to fluid saturations (k_r–S–P_c models) are of great importance for the modelling of sub-surface multi-phase flow and transport. In order to test their performance and to identify their important parameters, four well-known three-phase k_r–S–P_c models have been tested against published experimental data on non-aqueous phase liquid (NAPL) migration in the unsaturated zone. Both homogenous systems and systems with embedded heterogeneities have been analysed.  相似文献