Accelerated erosion in a watershed in the southeastern region of Brazil     

Mariana Dorici  Carlos Wilmer Costa  Mayra Cristina Prado de Moraes  Fabiola Geovanna Piga  Reinaldo Lorandi  José Augusto de Lollo  Luiz Eduardo Moschini 《Environmental Earth Sciences》2016,75(19):1301

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Predicting coffee yield based on agroclimatic data and machine learning     

de Oliveira Aparecido  Lucas Eduardo  Lorençone  João Antonio  Lorençone  Pedro Antonio  Torsoni  Guilherme Botega  Lima  Rafael Fausto  dade Silva CabralMoraes  José Reinaldo 《Theoretical and Applied Climatology》2022,148(3-4):899-914

Theoretical and Applied Climatology - Climate directly and indirectly influences agriculture, being the main responsible for low and high yields. Prior knowledge on yield helps coffee farmers in...  相似文献   

Cycles in the scaling properties of length-of-day variations     

Jose Alvarez-Ramirez  Leonardo Dagdug  Gonzalo Rojas 《Journal of Geodynamics》2010,49(2):105-110

Variations in the length-of-day (LOD) reflect the effects of several mechanisms in the Earth's rotation dynamics, including Earth–Sun and Earth–Moon line-up, geomagnetic effects and gravitational changes. Several studies showed that signatures of cycles occurring over a wide range of time scales are present in the LOD variations. The present work uses a fractal scaling study based on detrended fluctuation analysis (DFA) to study persistence of LOD variations and to provide insights in the different cycling mechanisms. The results showed that that the LOD variations are persistent over a wide range of time scales, meaning that an increment (resp., decrement) is more likely to be followed by an increment (resp., decrement). The temporal variation of the scaling exponent obtained from the DFA showed that several cycles already reported from the direct LOD variations analysis are inherited by the scaling properties. Inter-annual cycles, including 4.3 and 18.6 years cycles, are linked to the variations of the stochastic dynamics of LOD fluctuations. In this way, the 18.6 years cycle attains a period where variations are mostly affected by white noise effects, reducing the predictability of the LOD anomalies. The results are discussed in terms of the different lunar tidal and core–mantle mechanisms and related to recent results in the literature.  相似文献   

Gravitational radiation from cosmic string splitting on a Friedmann-Robertson-Walker background     

Reinaldo J. Gleiser  Andres D. Dagotto  Carlos O. Nicasio 《Astrophysics and Space Science》1991,178(2):303-309

We present exact solutions of Einstein's equations that may be interpreted as representing the splitting of a primordial cosmic string imbedded in a perfect fluid Friedmann-Robertson-Walker (FRW) cosmology. The splitting leads to the creation of a bubble whose boundary is given by a gravitational shock wave, expanding from the point of splitting, associated to the motion of the free ends of the string. Inside the bubble we have a perturbed FRW metric. This perturbation is largest near the string ends, producing a sort of wake along the path of the free ends, but decreases rapidly with time and the metric approaches the FRW regime locally everywhere inside the bubble. Similar results are shown to hold also for flat vacuum de Sitter space-times.Supported by a CONICET fellowship.Supported by a CONICOR fellowship.  相似文献   

Features of deep crustal structure and the onshore-offshore transition at the Iberian flank of the Valencia Trough (Western Mediterranean)     

J Gallart  H Rojas  J Diaz  J.J Daobeitia 《Journal of Geodynamics》1990,12(2-4)

First results are presented of a recent onshore seismic survey complementary to the Valsis-2 Cruise, which consisted of ESP, COP and CDP marine seismic profiles across the Valencia Trough (Western Mediterranean).The marine energy source used was an airgun array of 5800 cubic inch recorded at 2 land stations on the western flank of the Valencia Trough, at distances between 10–120 km.The experiment has resulted in an extended sampling of the deep crustal structure of the eastern Mediterranean flank of the Iberian peninsula, as well as the offshore-onshore transition.Three transverse NW-SE profiles have been interpreted. Local thinning of the sedimentary cover has been determined towards the centre of the basin which, together with the shallow high velocities observed on the southern profile, could be related to volcanic episodes.A seismic continental basement has been found at depths between 3 and 5 km. A thin lower crust (3–5 km) with velocities around 6.8 km/s has been identified in the northern part of the basin. Alternative crustal models considered for the 3 profiles have been tested, not only from arrival times but also from relative amplitude distributions. A first-order Moho discontinuity fits the data best. The welldefined Moho boundary results in energetic P_MP reflections, and a clear updoming is observed towards the interior of the basin, from depths about 20–21 km inshore of Barcelona to 15–17 km depths 60 km offshore. An anomalous upper mantle with low P_n velocities of about 7.7 km/s is confirmed in most of the sampled areas.  相似文献   

Substrate influence and temporal changes on periphytic biomass accrual and metabolism in a tropical humic lagoon     

Rafael D. Guariento  Adriano Caliman  Francisco A. Esteves  Reinaldo L. Bozelli  Alex Enrich-Prast  Vinicius F. Farjalla   《Limnologica》2009,39(3):209-218

We performed a field experiment in a tropical humic coastal lagoon to evaluate periphyton biomass accrual and metabolism on three different substrates (1) plastic ribbons, (2) green and (3) senescent leaves of the emergent macrophyte Typha domingensis) over 30 days. The contribution of autotrophic biomass decreased as total biomass increased over the time. Mean periphytic ash free dry weight ranged from 0.8 to 5.6 mg cm⁻², but periphyton chlorophyll a concentrations presented shorter amplitudes, which oscillated from 0.12 to 0.44 μg cm⁻² throughout the experiment. Periphyton metabolism was overall heterotrophic on all substrates, especially on senescent leaves. Our data show that substrate type influenced both biomass accrual and periphyton net productivity and respiration rates throughout periphyton development and highlighted the dominance of heterotrophic metabolism. The periphyton respiration may be subsidized by both water- and substrate-derived allochthonous energy pathways, shedding light on the role of periphytic assemblages to the carbon cycling, as a source of CO₂ to the system.  相似文献   

Faulting, shallow seismicity and seismic hazard analysis for the Costa Rican Central Valley     

M. Fernndez  W. Rojas 《Soil Dynamics and Earthquake Engineering》2000,20(1-4)

Faulting, shallow seismicity (0–30 km), and seismic hazard of the Costa Rican Central Valley were analyzed. Faults in the study area are oriented northwest or northeast. There is an active fault system in the south flank of the Central Volcanic Ridge and another in the north flank of the Talamanca Ridge. Faults of these systems have generated 15 destructive earthquakes in the area during the last 228 years all of them shallow and their locations show one cluster near the Poas Volcano and another southward the Central Valley. These earthquakes have damaged cities of the Central Valley, two of them destroyed Cartago city and almost 1000 people were killed. Regarding recent seismicity, there are three main seismic sources at the Central Volcanic Ridge: Irazu, Bajo de la Hondura and Poas and other three in the Talamanca Ridge: Puriscal, Los Santos and Pejibaye.A seismic hazard map for the Metropolitan Area of San José has been elaborated, based on local tectonic and seismic information. The area for the hazard computation covers an area of 20×15 km² and includes the zone where the most population and socioeconomic activities are concentrated. The computation analysis are based on areas zones and faults, each one characterized by recurrence parameters, geometry, minimum and maximum magnitude and source depth. A recent local spectral attenuation model, which includes relations for shallow crustal sources and subduction zone earthquakes, has been applied in this study. The seismic hazard results are presented in terms of contour plots of estimated peak ground acceleration (PGA) for bedrock conditions for return period of 50, 100 and 500 years. In the Central Park of San Jose City the following PGA values were found: 0.29g for 50 years, 0.36g for 100 years, and 0.53g for 500 years.  相似文献   

A genetic algorithm for filter design to enhance features in seismic images     

M.G. Orozco‐del‐Castillo  C. Ortiz‐Alemán  J. Urrutia‐Fucugauchi  R. Martin  A. Rodriguez‐Castellanos  P.E. Villaseñor‐Rojas 《Geophysical Prospecting》2014,62(2):210-222

We present a novel method to enhance seismic data for manual and automatic interpretation. We use a genetic algorithm to optimize a kernel that, when convolved with the seismic image, appears to enhance the internal characteristics of salt bodies and the sub‐salt stratigraphy. The performance of the genetic algorithm was validated by the use of test images prior to its application on the seismic data. We present the evolution of the resulting kernel and its convolved image. This image was analysed by a seismic interpreter, highlighting possible advantages over the original one. The effects of the kernel were also subject to an automatic interpretation technique based on principal component analysis. Statistical comparison of these results with those from the original image, by means of the Mann‐Whitney U‐test, proved the convolved image to be more appropriate for automatic interpretation.  相似文献   

The 16 September 2015 Chile Tsunami from the Post-Tsunami Survey and Numerical Modeling Perspectives     

Rafael Aránguiz  Gabriel González  Juan González  Patricio A. Catalán  Rodrigo Cienfuegos  Yuji Yagi  Ryo Okuwaki  Luisa Urra  Karla Contreras  Ian Del Rio  Camilo Rojas 《Pure and Applied Geophysics》2016,173(2):333-348

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A note on Einstein-Maxwell solutions and vacuum to electrovac solutions transforms     

Reinaldo J. Gleiser  Gabriela I. González  Jorge A. Pullin 《Astrophysics and Space Science》1988,149(2):369-373

We discuss a direct construction of solitonic solutions in the Einstein-Maxwell system and analyze the connection of these with vacuum to electrovac transforms of the usual Belinskii-Zakharov vacuum solutions in the static and Einstein-Rosen waves cases.It should be noted that the construction of Belinskii is the same as the one that appears in the Kaluza-Klein ansatz, although in his case there is no direct interpretation to the scalarg ₅₅ fieldSupported by a CONICET fellowship.  相似文献