2,567 research outputs found
Gross output and livestock sales modelling in Spanish extensive farms using PLSR
The aim of this paper is to model some production variables in extensive livestock farms located in the dehesa ecosystem. We intend to use not only purely economic variables in the construction of the model, but also structural variables in order to identify the characteristics of the farms that have the higher influence. Another objective is to be able to predict these variables at the farm level, using structural variables that are easy to measure. The data used in this work were obtained from a questionnaire survey to the holders/managers of a sample of 69 dehesa farms in Extremadura (SW Spain). The statistical methodology used for the construction of the model was Partial Least Square Regression (PLSR). It can be concluded that the variables relative to farm intensification, to labour and especially to Iberian pig breeding, are those that take part mainly in the model.dehesa, livestock farming systems, partial least square regression, gross output, Crop Production/Industries, Livestock Production/Industries, Research Methods/ Statistical Methods,
Economic Costs of Sustaining Water Supplies: Findings from the Rio Grande
[EN] Water claims in many of the world's arid basins exceed reliable supplies. Water demands for irrigation, urban use, the environment, and energy continue to grow, while supplies remain constrained by unsustainable use, drought and impacts of climate change. For example, policymakers in North America's Upper Rio Grande Basin face the challenge of designing plans for allocating the basin's water supplies efficiently and fairly to support current uses and current environments. Managers also seek resilient institutions that can ensure adequate supplies for future generations. This paper addresses those challenges by designing and applying an integrated basin-scale framework that accounts for the basin's most important hydrologic, economic, and institutional constraints. Its unique contribution is a quantitative analysis of three policies for addressing long term goals for the basin's reservoirs and aquifers: (1) no sustainability for water stocks, (2) sustaining water stocks, and (3) renewing water stocks. It identifies water use and allocation trajectories over time that result from each of these three plans. Findings show that it is hydrologically and institutionally feasible to manage the basin's water supplies sustainably. The economic cost of protecting the sustainability of the basin's water stocks can be achieved at 6-11 percent of the basin's average annual total economic value of water over a 20 year time horizon.The authors are grateful for financial support for this work by the New Mexico Agricultural Experiment Station and by the European Community 7th Framework Project GENESIS (226536) on Groundwater SystemsWard, FA.; Pulido-Velazquez, M. (2012). Economic Costs of Sustaining Water Supplies: Findings from the Rio Grande. Water Resources Management. 26(10):2883-2909. https://doi.org/10.1007/s11269-012-0055-8288329092610Booker JF (1995) Hydrologic and economic impacts of drought under alternative policy responses. Water Resour Bull 31:889–906Booker JF, Young RA (1994) Modeling intrastate and interstate markets for colorado river water resources. J Environ Econ Manag 26:66–87Booker JF, Michelsen AM, Ward FA (2005) Economic impact of alternative policy responses to prolonged and severe drought in the Rio Grande Basin. Water Resour Res 41:W02026Brown T (1990) Marginal economic value of streamflow: a case study for the Colorado River Basin. Water Resour Res 26:2845–2859Brown GM (2000) Renewable natural resource management and use without markets. J Econ Lit 38:875–914Burke SM, Adams RM, Wallender WW (2004) Water banks and environmental water, and demands: case of the Klamath Project. Water Resour Res 40:2004Cai X, Rosegrant MW (2004) Irrigation technology choices under hydrologic uncertainty: a case study from Maipo River Basin, Chile. Water Resour Res 40:W04103. doi: 04110.01029/02003WR002810Cai X, Ringler C, Rosegrant M (2006) Modeling water resources management at the basin level: Methodology and application to the maipo river basin research report. 149 International Food Policy Research Institute, Washington DCCharacklis GW, Griffin RC, Bedient PB (1999) Improving the ability of a water market to efficiently manage drought. Water Resour Res 35:823–831City of Albuquerque Water Utilities (2011) On the web at: http://www.cabq.gov/water/Draper AJ, Jenkins MW, Kirby KW, Lund JR, Howitt RE (2003) Economic engineering optimization for California water management. J Water Res PL-Manag 129:155–164Elephant Butte Irrigation District (2011) On the web at: http://www.ebid-nm.orgEl-Naqa A, Al-Shayeb A (2009) Groundwater protection and management strategy in Jordan. Water Resour Manag 23:2379–2394El Paso County Water Improvement District #1 (2011) On the web at: www.epcwid1.orgEl Paso Water Utilities (2011) On the web at: http://www.epwu.orgFlugel WA (2007) The adaptive integrated data information system (AIDIS) for global water research. Water Resour Manag 21:199–210Gohar A, Ward FA (2010) Gains from expanded irrigation water trading in Egypt: an integrated basin approach. Ecol Econ 69:2535–2548Gürlük S, Ward FA (2009) Integrated basin management: water and food policy options for Turkey. Ecol Econ 68:2666–2678Hawkes JM, Libbin JD (2011) Cost and Return Estimates. November 12 at http://aces.nmsu.edu/cropcosts/Jenkins MW, Lund JR, Howitt RE, Draper AJ, Msangi SM, Tanaka SK, Ritzema RS, Marques GF (2004) Optimization of California’s Water System: results and insights. J Water Resour Pl-Manag 130:271–280Knapp KC, Weinberg M, Howitt RE, Posnikoff JF (2003) Water transfers, agriculture and groundwater management: A dynamic economic analysis. J Environ Manag 67:291–301Koundouri P (2004) Current issues in the economics of groundwater resource management. J Econ Surv 18:703–740Letcher RA, Jakeman AJ, Croke BFW (2004) Model development for intgegrated assessment of water allocation options. Water Resour Res 40:W05502. doi: 05510.01029/02003WR002933Livingston ML, Garrido A (2004) Entering the policy debate: an economic valuation of groundwater policy in flux. Water Resour Res 40:W12S02Lund J, Guzman J (1999) Some derived operating rules for reservoirs in series or in parallel. J Water Resour Pl-Manag 125:143–153McCarl BA, Dillon CR, Keplinger KO, Williams RL (1999) Limiting pumping from the edwards aquifer: an economic investigation of proposals, water markets, and spring flow guarantees. Water Resour Res 35:1257–1268Michelsen A, McGuckin T, Stumpf D (1999) Nonprice water conservation programs as a demand management tool. J Am Water Resour Assoc 35:593–602Middle Rio Grande Conservancy District (2011) On the web at: http://www.mrgcd.comMolina JL, Arostegui JLG, Benavente J, Varela C, de la Hera A, Geta JAL (2009) Aquifers overexploitation in SE Spain: a proposal for the integrated analysis of water management. Water Resour Manag 23:2737–2760Murad AA, Al Nuaimi H, Al Hammadi M (2007) Comprehensive assessment of water resources in the united arab emirates (UAE). Water Resour Manag 21:1449–1463National Research Council (1997) Valuing ground water: economic concepts and approaches. National Academic Press, WashingtonNewlin BD, Jenkins MW, Lund JR, Howitt RE (2002) Southern California water markets: potential and limitations. J Water Resour Pl-Manag 128:21–32New Mexico Water Resources Research Institute (2006) Rio Grande Compact TextPascual P (2007) Avoiding tragedies of the intellectual commons through Integrated Impact Assessments. Water Resour Manag 21:2005–2013Prodanovic P, Simonovic SP (2011) An operational model for support of integrated watershed management. Water Resour Manag 24:1161–1194Pulido-Velazquez M, Jenkins MW, Lund JR (2004) Economic values for conjunctive use and water banking in Southern California. Water Resour Res 40(3):W03401Pulido-Velazquez M, Andreu J, Sahuquillo A (2006) Economic optimization of conjunctive use of surface water and groundwater at the basin scale. J Water Resour Pl-Manag 132(6):454–467Ringler CJ, von Braun J, Rosegrant MW (2004) Water policy analysis for the Mekong River Basin. Water Int 29:30–42Rio Grande Water Conservation District (2011) On the web at: http://www.rgwcd.orgSchulze RE (2007) Some foci of integrated water resources management in the “south” which are oft-forgotten by the “north”: a perspective from southern Africa. Water Resour Manag 21:269–294Speed R (2009) Transferring and trading water rights in the People's Republic of China. Int J Water Resour Dev 25:(2)269–281Tanaka SK, Zhu T, Lund JR, Howitt RE, Jenkins MW, Pulido-Velazquez M, Tauber M, Ritzema RS, Ferreira IC (2006) Climate warming and water management adaptation for California. Climatic Change 76:361–384Tietenberg T, Lewis L (2009) Environmental and natural resource economics, 8th edn. Prentice-HallTorell G, Ward FA (2010) Improved water institutions for food security and rural livelihoods in Afghanistan’s Balkh River Basin. Int J Water Resour Dev 26:613–637van der Keur P, Henriksen HJ, Refsgaard JC, Brugnach M, Pahl-Wostl C, Dewulf A, Buiteveld H (2008) Identification of major sources of uncertainty in current IWRM practice. Illustrated for the Rhine basin. Water Resour Manag 22:1677–1708Ward FA, Lynch TP (1997) Is dominant use management compatible with basin-wide economic efficiency? Water Resour Res 33:1165–1170Ward FA, Pulido-Velazquez M (2008) Efficiency, equity and sustainability in a water quantity-quality optimization model in the Rio Grande basin. Ecol Econ 66:26–37Ward FA, Pulido-Velazquez M (2009) Incentive pricing and cost recovery at the basin scale. J Environ Manag 90(1):293–313Ward FA, Cole RA, Deitner RA, Green-Hammond KA (1997) Limiting environmental program contradictions: a demand systems application to fishery management. Am J Agr Econ 79:803–813Ward FA, Booker JF, Michelsen AM (2006) Integrated economic, hydrologic, and institutional analysis of policy responses to mitigate drought impacts in the Rio Grande Basin. J Water Resour Pl-Manag 132:488–502Watkins DW Jr., McKinney DC (1999) Screening water supply options for the edwards aquifer region in Central Texas. J Water Resour Pl-Manag 125:14–24Watkins DW, Moser DA (2006) Economic-based optimization of panama canal system operations. J Water Resour Pl-Manag 132:454–467Willis DB, Whittlesey NK (1998) Water management policies for streamflow augmentation in an irrigated River Basin. J Agr Resour Econ 23:170–190Young RA (2005) Determining the economic value of water: concepts and methods. Washington D.C, USA: Resources For the FutureZarghaami M (2006) Integrated water resources management in polrud irrigation system. Water Resour Manag 20:215–22
Experimental Synthetic Aperture Radar with Dynamic Metasurfaces
We investigate the use of a dynamic metasurface as the transmitting antenna
for a synthetic aperture radar (SAR) imaging system. The dynamic metasurface
consists of a one-dimensional microstrip waveguide with complementary electric
resonator (cELC) elements patterned into the upper conductor. Integrated into
each of the cELCs are two diodes that can be used to shift each cELC resonance
out of band with an applied voltage. The aperture is designed to operate at K
band frequencies (17.5 to 20.3 GHz), with a bandwidth of 2.8 GHz. We
experimentally demonstrate imaging with a fabricated metasurface aperture using
existing SAR modalities, showing image quality comparable to traditional
antennas. The agility of this aperture allows it to operate in spotlight and
stripmap SAR modes, as well as in a third modality inspired by computational
imaging strategies. We describe its operation in detail, demonstrate
high-quality imaging in both 2D and 3D, and examine various trade-offs
governing the integration of dynamic metasurfaces in future SAR imaging
platforms
Infrared Study of Fullerene Planetary Nebulae
We present a study of 16 PNe where fullerenes have been detected in their
Spitzer spectra. This large sample of objects offers an unique opportunity to
test conditions of fullerene formation and survival under different metallicity
environments as we are analyzing five sources in our own Galaxy, four in the
LMC, and seven in the SMC. Among the 16 PNe under study, we present the first
detection of C60 (possibly also C70) fullerenes in the PN M 1-60 as well as of
the unusual 6.6, 9.8, and 20 um features (possible planar C24) in the PN K
3-54. Although selection effects in the original samples of PNe observed with
Spitzer may play a potentially significant role in the statistics, we find that
the detection rate of fullerenes in C-rich PNe increases with decreasing
metallicity (5% in the Galaxy, 20% in the LMC, and 44% in the SMC). CLOUDY
photoionization modeling matches the observed IR fluxes with central stars that
display a rather narrow range in effective temperature (30,000-45,000 K),
suggesting a common evolutionary status of the objects and similar fullerene
formation conditions. The observed C60 intensity ratios in the Galactic sources
confirm our previous finding in the MCs that the fullerene emission is not
excited by the UV radiation from the central star. CLOUDY models also show that
line- and wind-blanketed model atmospheres can explain many of the observed
[NeIII]/[NeII] ratios by photoionization suggesting that possibly the UV
radiation from the central star, and not shocks, are triggering the
decomposition of the circumstellar dust grains. With the data at hand, we
suggest that the most likely explanation for the formation of fullerenes and
graphene precursors in PNe is that these molecular species are built from the
photo-chemical processing of a carbonaceous compound with a mixture of aromatic
and aliphatic structures similar to that of HAC dust.Comment: Accepted for publication in ApJ (43 pages, 11 figures, and 4 tables).
Small changes to fit the proof-corrected article to be published in Ap
Sustainability of organic and conventional beef cattle farms in SW Spanish rangelands (‘dehesas’): a comparative study
Organic production in Spain has increased substantially in recent years due to several factors, such as the growing interest of the European Union towards preserving sensitive ecosystems; the potential role of organic production in the socio-economic development of rural areas and the growing consumers' demand for safer and higher quality foods. Within this framework, this paper analyzes the beef sector of SW Spanish rangelands (dehesas). These are traditional systems characteristic of the Iberian Peninsula where native herbaceous vegetation and evergreen species of Quercus provide the basis for extensive beef farms. Alt-hough traditional management in dehesa farms is of vital importance for the sustainability of this particular ecosystem, in the last years many farms have turned to organic production, trying to take advantage both of new subsidies and of new market trends.With this study, we try to evalu-ate the sustainability of conventional and organic beef production systems in dehesas in Extre-madura (SW Spain), trying to determine the level these systems are contributing both to the preservation of this sensitive ecosystem and to the socioeconomic development of the region. To this end, we apply a methodological adaptation of the MESMIS methodology to 90 dehesa beef farms located in Extremadura (SW Spain). MESMIS is based on the evaluation of basic attributes of sustainability that allow one to make a simultaneous and comparative analysis of different types of farms. It has been found that organic farms are the most sustainable, obtaining higher scores than con-ventional farms in stability and self-reliance, and similar scores in productivity, adaptability, and equity. Organic dehesa beef farms show little dependence on external products and services and are more adapted to their environment (lower stocking rates for an optimal use of the system's feedstuff production), those being the clues for their enhanced sustainability
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