1,140 research outputs found

    Analysis, assessment, and improvement of fertilizer distribution in pressure irrigation systems

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    [EN] The transformation of traditional irrigation systems into pressure irrigation networks allows water users associations to use central fertigation systems. For efficient fertigation management, however, it is essential to obtain uniform distribution of the injected fertilizer through the system and to understand the hydraulic processes that take place in the central fertigation system. This will allow users to implement strategies that improve fertilizer distribution. In this work we develop a new methodology to improve fertilizer distribution uniformity and apply it to a case study. The results show how fertilizer distribution can be improved by means of proper scheduling of irrigation deliveries. The best results are obtained when fertigating sectors operate without non-fertigating sectors and there are not intermediate irrigations without fertilizer, achieving an improvement of the fertilizer distribution of 10.5%. In addition, this work highlights the difficulties of obtaining uniform distribution of fertilizer in a centralized irrigation system when there are users that do not want to make use of it.Jiménez Bello, MA.; Martínez Alzamora, F.; Bou Soler, V.; Bartolín Ayala, HJ. (2010). Analysis, assessment, and improvement of fertilizer distribution in pressure irrigation systems. Irrigation Science. 29(1):45-53. doi:10.1007/s00271-010-0215-7S4553291Arviza J y Balbastre I (2002a) “Redes de Riego a presión. Consideraciones sobre la fertirrigación colectiva”. Revista Levante Agrícola nº 359. 1º trimestre. Págs. 70–81. Ediciones y promociones LAV SL. ValenciaArviza J y Balbastre I (2002b) “Redes de Riego a presión. Consideraciones sobre la fertirrigación colectiva. Parte II”. Revista Levante Agrícola nº 360. 2º trimestre. Págs. 133–139. Ediciones y promociones LAV SL. ValenciaArviza J, Martínez F, y Balbastre I (2002) Análisis de la distribución de fertilizantes en sistemas colectivos de riego a presión. XX Congreso Nacional de Riegos. Ciudad Real. EspañaBracy RP, Parish RL, Rosendale RM (2003) Fertigation uniformity affected by injector type. Horttechnology 13:103–105Goldberg DE (1989) Genetic algorithms in search, optimization and machine learning. Addison-Wesley, ReadingJiménez MA, Martínez F, Arviza J, Manzano J (2006) Herramientas para el uso racional del agua con el apoyo de un GIS (HuraGIS). XXIV. Congreso nacional de riegos. Lugo (Spain). (Jun 2006)Jiménez MA, Martínez F, Arviza J, Manzano J (2008) Optimización de la sectorización de redes de riego a presión mediante algoritmos genéticos XXVI. Congreso nacional de riegos. Huesca. (Jun 2008)Jiusheng L, Yibin M, Bei L (2007) Field evaluation of fertigation uniformity as affected by injector type and manufacturing variability of emitters. Irrigation Sci 25:117–125Kalyanmoy D (2001) Multi-objective optimization using evolutionary algorithms. Willey, EnglandRossman LA (2000) Epanet 2, Users Manual. Water Supply and Water Resources Division. National Risk Management Research Laboratory, CincinnatiSavic D, Walters G (1997) Genetic algorithms for least-cost design of water distribution networks. J Water Resour Plann Manag 123(2):67–77 (March/April 1997

    Impacts of the Tropical Pacific/Indian Oceans on the Seasonal Cycle of the West African Monsoon

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    The current consensus is that drought has developed in the Sahel during the second half of the twentieth century as a result of remote effects of oceanic anomalies amplified by local land–atmosphere interactions. This paper focuses on the impacts of oceanic anomalies upon West African climate and specifically aims to identify those from SST anomalies in the Pacific/Indian Oceans during spring and summer seasons, when they were significant. Idealized sensitivity experiments are performed with four atmospheric general circulation models (AGCMs). The prescribed SST patterns used in the AGCMs are based on the leading mode of covariability between SST anomalies over the Pacific/Indian Oceans and summer rainfall over West Africa. The results show that such oceanic anomalies in the Pacific/Indian Ocean lead to a northward shift of an anomalous dry belt from the Gulf of Guinea to the Sahel as the season advances. In the Sahel, the magnitude of rainfall anomalies is comparable to that obtained by other authors using SST anomalies confined to the proximity of the Atlantic Ocean. The mechanism connecting the Pacific/Indian SST anomalies with West African rainfall has a strong seasonal cycle. In spring (May and June), anomalous subsidence develops over both the Maritime Continent and the equatorial Atlantic in response to the enhanced equatorial heating. Precipitation increases over continental West Africa in association with stronger zonal convergence of moisture. In addition, precipitation decreases over the Gulf of Guinea. During the monsoon peak (July and August), the SST anomalies move westward over the equatorial Pacific and the two regions where subsidence occurred earlier in the seasons merge over West Africa. The monsoon weakens and rainfall decreases over the Sahel, especially in August.Peer reviewe

    Severe early onset preeclampsia: short and long term clinical, psychosocial and biochemical aspects

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    Preeclampsia is a pregnancy specific disorder commonly defined as de novo hypertension and proteinuria after 20 weeks gestational age. It occurs in approximately 3-5% of pregnancies and it is still a major cause of both foetal and maternal morbidity and mortality worldwide1. As extensive research has not yet elucidated the aetiology of preeclampsia, there are no rational preventive or therapeutic interventions available. The only rational treatment is delivery, which benefits the mother but is not in the interest of the foetus, if remote from term. Early onset preeclampsia (<32 weeks’ gestational age) occurs in less than 1% of pregnancies. It is, however often associated with maternal morbidity as the risk of progression to severe maternal disease is inversely related with gestational age at onset2. Resulting prematurity is therefore the main cause of neonatal mortality and morbidity in patients with severe preeclampsia3. Although the discussion is ongoing, perinatal survival is suggested to be increased in patients with preterm preeclampsia by expectant, non-interventional management. This temporising treatment option to lengthen pregnancy includes the use of antihypertensive medication to control hypertension, magnesium sulphate to prevent eclampsia and corticosteroids to enhance foetal lung maturity4. With optimal maternal haemodynamic status and reassuring foetal condition this results on average in an extension of 2 weeks. Prolongation of these pregnancies is a great challenge for clinicians to balance between potential maternal risks on one the eve hand and possible foetal benefits on the other. Clinical controversies regarding prolongation of preterm preeclamptic pregnancies still exist – also taking into account that preeclampsia is the leading cause of maternal mortality in the Netherlands5 - a debate which is even more pronounced in very preterm pregnancies with questionable foetal viability6-9. Do maternal risks of prolongation of these very early pregnancies outweigh the chances of neonatal survival? Counselling of women with very early onset preeclampsia not only comprises of knowledge of the outcome of those particular pregnancies, but also knowledge of outcomes of future pregnancies of these women is of major clinical importance. This thesis opens with a review of the literature on identifiable risk factors of preeclampsia

    Penilaian Kinerja Keuangan Koperasi di Kabupaten Pelalawan

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    This paper describe development and financial performance of cooperative in District Pelalawan among 2007 - 2008. Studies on primary and secondary cooperative in 12 sub-districts. Method in this stady use performance measuring of productivity, efficiency, growth, liquidity, and solvability of cooperative. Productivity of cooperative in Pelalawan was highly but efficiency still low. Profit and income were highly, even liquidity of cooperative very high, and solvability was good

    Measurements of the pp → ZZ production cross section and the Z → 4ℓ branching fraction, and constraints on anomalous triple gauge couplings at √s = 13 TeV

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    Four-lepton production in proton-proton collisions, pp -> (Z/gamma*)(Z/gamma*) -> 4l, where l = e or mu, is studied at a center-of-mass energy of 13 TeV with the CMS detector at the LHC. The data sample corresponds to an integrated luminosity of 35.9 fb(-1). The ZZ production cross section, sigma(pp -> ZZ) = 17.2 +/- 0.5 (stat) +/- 0.7 (syst) +/- 0.4 (theo) +/- 0.4 (lumi) pb, measured using events with two opposite-sign, same-flavor lepton pairs produced in the mass region 60 4l) = 4.83(-0.22)(+0.23) (stat)(-0.29)(+0.32) (syst) +/- 0.08 (theo) +/- 0.12(lumi) x 10(-6) for events with a four-lepton invariant mass in the range 80 4GeV for all opposite-sign, same-flavor lepton pairs. The results agree with standard model predictions. The invariant mass distribution of the four-lepton system is used to set limits on anomalous ZZZ and ZZ. couplings at 95% confidence level: -0.0012 < f(4)(Z) < 0.0010, -0.0010 < f(5)(Z) < 0.0013, -0.0012 < f(4)(gamma) < 0.0013, -0.0012 < f(5)(gamma) < 0.0013

    Search for heavy resonances decaying to two Higgs bosons in final states containing four b quarks

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    A search is presented for narrow heavy resonances X decaying into pairs of Higgs bosons (H) in proton-proton collisions collected by the CMS experiment at the LHC at root s = 8 TeV. The data correspond to an integrated luminosity of 19.7 fb(-1). The search considers HH resonances with masses between 1 and 3 TeV, having final states of two b quark pairs. Each Higgs boson is produced with large momentum, and the hadronization products of the pair of b quarks can usually be reconstructed as single large jets. The background from multijet and t (t) over bar events is significantly reduced by applying requirements related to the flavor of the jet, its mass, and its substructure. The signal would be identified as a peak on top of the dijet invariant mass spectrum of the remaining background events. No evidence is observed for such a signal. Upper limits obtained at 95 confidence level for the product of the production cross section and branching fraction sigma(gg -> X) B(X -> HH -> b (b) over barb (b) over bar) range from 10 to 1.5 fb for the mass of X from 1.15 to 2.0 TeV, significantly extending previous searches. For a warped extra dimension theory with amass scale Lambda(R) = 1 TeV, the data exclude radion scalar masses between 1.15 and 1.55 TeV
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