The Role of Coffee in the Development of Southwest Ethiopia's Forests: Farmers' Strategies,Investor Speculation,and Certification Projects     

Samir El Ouaamari  Hubert Cochet 《社会与自然资源》2014,27(2):200-214

This article examines the role of coffee in the agriculture of southwest Ethiopian highlands, a context characterized by recent huge private coffee estate developments, coffee certification projects and smallholdings. The analysis shows that smallholder farmers prioritize staple crops, and allocate land and labor to coffee only once food production objectives have been reached. It also underscores the diversity of the local peasantry, often treated as a homogeneous group in development projects designed to boost farmers' income through coffee production. Based on this analysis, the article evaluates the effects of recent coffee-oriented development policies: state forest concessions for coffee investment, and two coffee certification projects (UTZ-Certified and Fair-Trade/Organic). Because they omit the differentiated farmers' strategies, these certification initiatives fail to improve local populations' livelihoods and accelerate incipient socioeconomic inequalities. Moreover, when applied to big private plantations, they participate in farmers' dispossession from critical forest resources essential to households' food self-sufficiency.  相似文献   

A study of aerosol properties over Lahore (Pakistan) by using AERONET data     

Muhammad Ali  Salman Tariq  Khalid Mahmood  Asim Daud  Adila Batool  Zia-ul-Haq 《Asia-Pacific Journal of Atmospheric Sciences》2014,50(2):153-162

It is well established that aerosols affect the climate in a variety of ways. In order to understand these effects, we require an insight into the properties of aerosols. In this paper we present a study of aerosol properties such as aerosol optical depth (AOD), single scattering albedo (SSA) and aerosol radiative forcing (ARF) over mega city of Lahore (Pakistan). The data from Aerosol Robotic Network (AERONET) have been used for the period December 2009 to October 2011. The seasonal average values of AOD, asymmetry parameter (ASY) and volume size distribution in coarse mode were observed to be highest in summer. On the other hand, the average values of Angstrom exponent (AE) and imaginary part of refractive index (RI) were found to be maximum in winter. The average value of real part of RI was found to be higher in spring than in all other seasons. The SSA exhibited an increasing trend with wavelength in the range 440 nm–1020 nm in spring, summer and fall indicating the dominance of coarse particles (usually dust). However, a decreasing trend was found in winter in the range 675 nm–1020 nm pointing towards the dominance of biomass and urban/industrial aerosols. As far as aerosol radiative forcing (ARF) is concerned, we have found that during the spring season ARF was lowest at the surface of Earth and highest at top of the atmosphere (TOA). This indicates that the atmosphere was warmer in spring than in all the remaining seasons.  相似文献   

Streaming potential in a deformed porous medium and geophysical applications     

I. N. El’tsov  V. V. Shelukhin  M. I. Epov 《Doklady Earth Sciences》2014,454(2):189-192

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Adjoint formulation and constraint handling for gradient-based optimization of compositional reservoir flow     

Drosos Kourounis  Louis J. Durlofsky  Jan Dirk Jansen  Khalid Aziz 《Computational Geosciences》2014,18(2):117-137

An adjoint formulation for the gradient-based optimization of oil–gas compositional reservoir simulation problems is presented. The method is implemented within an automatic differentiation-based compositional flow simulator (Stanford’s Automatic Differentiation-based General Purpose Research Simulator, AD-GPRS). The development of adjoint procedures for general compositional problems is much more challenging than for oil–water problems due to the increased complexity of the code and the underlying physics. The treatment of nonlinear constraints, an example of which is a maximum gas rate specification in injection or production wells, when the control variables are well bottom-hole pressures, poses a particular challenge. Two approaches for handling these constraints are presented—a formal treatment within the optimizer and a simpler heuristic treatment in the forward model. The relationship between discrete and continuous adjoint formulations is also elucidated. Results for four example cases of increasing complexity are presented. Improvements in the objective function (cumulative oil produced) relative to reference solutions range from 4.2 to 11.6 %. The heuristic treatment of nonlinear constraints is shown to offer a cost-effective means for obtaining feasible solutions, which are, in some cases, better than those obtained using the formal constraint handling procedure.  相似文献   

Diagenesis of Holocene beachrocks: a comparative study between the Arabian Gulf and the Gulf of Aqaba,Saudi Arabia     

Khalid Al-Ramadan 《Arabian Journal of Geosciences》2014,7(11):4933-4942

Beachrocks occur in present-day intertidal zones of the Arabian Gulf and the Gulf of Aqaba, on the eastern and northwestern coasts, respectively, of Saudi Arabia. The beachrocks occur as linear patches within beach deposits, which have variable grain size and detrital compositions. The Arabian Gulf beachrocks are composed of sand-sized bioclasts and siliciclastic grains, whereas the Gulf of Aqaba beachrocks are composed of sand- to pebble-size grains, which are dominated by igneous rock fragments and small amounts of skeletal carbonate grains. The cement includes micritic high-magnesian calcite and isopachous acicular/bladed aragonite. In addition to cements, intergranular pores are locally filled by a lime–mud matrix. Radiocarbon dating of beachrock samples from the Arabian Gulf yielded ages from ca. 655 to 2185 year bp, whereas the Gulf of Aqaba samples range in age between 2745 and 5075 year bp.  相似文献   

Tectonic evolution of the Southern Gulf of Suez, Egypt: a comparison between depocenter and near peripheral basins   总被引：1，自引：0，他引：1  

Mohamed A. Omran  Mohamed S. El Sharawy 《Arabian Journal of Geosciences》2014,7(1):87-107

The sedimentary pattern of the southern Gulf of Suez, Egypt, especially during the Cenozoic rift stage, was controlled mainly by tectonic activities (subsidence and uplift) and sea level change. The stratigraphic record of the southern Gulf of Suez can be divided into two megasequences: pre-rift and syn-rift. The pre-rift megasequence can be viewed as two distinctive depositional regimes, clastic rocks of continental to braided stream environment during Cambrian and open marine transgression extended from Upper Cretaceous till Eocene. The syn-rift deposits showed a distinctive contrast between the depocenter and peripheral basins. This difference can be shown clearly on the sedimentary sequence of Hilal and Shoab Ali oilfields. The syn-rift megasequence can be differentiated in relation to rift evolution into the following stages: initial rift stage with low subsidence rate, main rift stage with maximum subsidence rate, quiescence stage with the slowest subsidence rate throughout the rift evolution, evaporite stage with restriction conditions, and Pliocene–Recent stage with shallow marine condition.  相似文献   

Alp Transit: Crossing Faults 44 and 49     

M. El Tani  R. Bremen 《Rock Mechanics and Rock Engineering》2014,47(3):1037-1048

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Performance of Foundations in Sabkha Soil: Numerical Investigation   总被引：1，自引：1，他引：0  

Ahmed M. Alnuaim  M. H. El Naggar 《Geotechnical and Geological Engineering》2014,32(3):637-656

Sabkha or salt flat soil is one of the most unpredictable and potentially dangerous soils in the Middle East. This soil covers a large and strategically important area of the Arabian Gulf coast, as it contains the world biggest oil reserve and a number of petrochemical plants are either have been built or are scheduled to be built in this area. The performance of shallow and deep foundations in the Eastern Province of Saudi Arabia’s sabkha soil is investigated numerically using the finite element method. The parameters used to simulate this soil in the numerical models were based on a large number of laboratory tests to determine the shear strength and stiffness parameters of the sabkha soil. In addition, the characteristics of the interface between the foundation and soil used in the numerical model were established from shear box tests that were conducted to evaluate the concrete-sabkha soil interface properties. The developed numerical model was calibrated/verified using the results of full-scale pile load testing program from an ongoing project to further enhance the accuracy of the results. A parametric study was then conducted using the verified model to establish the performance characteristics of foundations constructed in sabkha soil and provide guidelines for their design.  相似文献   

Factors and processes of permanent gully evolution in a Mediterranean marly environment (Cape Bon,Tunisia)     

A. El Khalili  H. Habaeib  J. M. Lamachère 《水文科学杂志》2013,58(7):1519-1531

Abstract

Gully erosion is considered to be one of the most important soil erosion processes in Mediterranean marly environments, but its actual contribution to total soil loss is still under discussion. The objectives of this paper are: (a) to acquire the distributed value of erosion rate in a permanent gully developed on a marly substratum in a Mediterranean environment; and (b) to quantify the key factors responsible for the spatial and temporal differences in erosion rates observed within the gully. A permanent gully located in Cap Bon (northeastern Tunisia) has been intensively and regularly monitored over a 7-year period with electronic survey equipment (total station) to give five field topographic surveys, as well as hydrological measurements at the gully outlet. The net soil loss for the 7-year period comprised a denudation of 51 m³ of sediment on the gully bank slopes, which corresponds to a mean soil loss of 61 m³ ha^?1 year^?1 or 6.1 mm year^?1. Denudation was observed on bed units with a slope gradient greater than 20%, while the remainder showed deposition. By confirming the factors involved in gully evolution, and by refining the statistical link between factors and erosion rates within the gully, the results provide important information to predict gully erosion rates in Mediterranean marly environments.

Editor Z.W. Kundzewicz; Associate editor G. Mahé

Citation El Khalili, A., Raclot, D., Habaieb, H., and Lamachère, J.M., 2013. Factors and processes of permanent gully evolution in a Mediterranean marly environment (Cape Bon, Tunisia). Hydrological Sciences Journal, 58 (7), 1519–1531.  相似文献   

Origin of EL3 chondrites: Evidence for variable C/O ratios during their course of formation—A state of the art scrutiny          下载免费PDF全文

A. El Goresy  Y. Lin  M. Miyahara  A. Gannoun  M. Boyet  E. Ohtani  P. Gillet  M. Trieloff  A. Simionovici  L. Feng  L. Lemelle 《Meteoritics & planetary science》2017,52(5):781-806

Mineral inventories of enstatite chondrites; (EH and EL) are strictly dictated by combined parameters mainly very low dual oxygen (fO₂) and sulfur (fS₂) fugacities. They are best preserved in the Almahata Sitta MS‐17, MS‐177 fragments, and the ALHA 77295 and MAC 88136 Antarctic meteorites. These conditions induce a stark change of the geochemical behavior of nominally lithophile elements to chalcophile or even siderophile and changes in the elemental partitioning thus leading to formation of unusual mineral assemblages with high abundance of exotic sulfide species and enrichment in the metallic alloys, for example, silicides and phosphides. Origin and mode of formation of these exotic chondrites, and their parental source regions could be best scrutinized by multitask research experiments of the most primitive members covering mineralogical, petrological, cosmochemical, and indispensably short‐lived isotopic chronology. The magnitude of temperature and pressure prevailed during their formation in their source regions could eventually be reasonably estimated: pre‐ and postaccretionary could eventually be deduced. The dual low fugacities are regulated by the carbon to oxygen ratios estimated to be >0.83 and <1.03. These parameters not only induce unusual geochemical behavior of the elements inverting many nominally lithophile elements to chalcophile or even siderophile or anthracophile. Structure and mineral inventories in EL3 and EH3 chondrites are fundamentally different. Yet EH3 and EL3 members store crucial information relevant to eventual source regions and importantly possible variation in C/O ratio in the course of their evolution. EL3 and EH3 chondrites contain trichotomous lithologies (1) chondrules and their fragments, (2) polygonal enstatite‐dominated objects, and (3) multiphase metal‐rich nodules. Mineralogical and cosmochemical inventories of lithologies in the same EL3 indicate not only similarities (REE inventory and anomalies in oldhamite) but also distinct differences (sinoite‐enstatite‐graphite relationship). Oldhamite in chondrules and polygonal fragments in EL3 depict negative Eu anomaly attesting a common cosmochemical source. Metal‐dominated nodules in both EL3 and EH3 are conglomerates of metal clasts and sulfide fragments in EH3 and concentrically zoned C‐bearing metal micropebbles (≥25 μm ≤50 μm) in EL3 thus manifesting a frozen in unique primordial accretionary metal texture and composition. Sinoite‐enstatite‐diopside‐graphite textures reveal a nucleation and growth strongly suggestive of fluctuating C/O ratio during their nucleation and growth in the source regions. Mineral inventories, sulfide phase relations, sinoite‐enstatite‐graphite intergrowth, carbon and nitrogen isotopic compositions of graphite, spatial nitrogen abundance in graphite in metal nodules, and last but not least ¹²⁹I/¹²⁹Xe and ⁵³Mn/⁵³Cr systematics negate any previously suggested melting episode, pre‐accretionary or dynamic, in parental asteroids.  相似文献