Probabilistic long-term reservoir operation employing copulas and implicit stochastic optimization     

&#;vila  Leandro  Mine  Miriam R. M  Kaviski  Eloy 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(7):931-947

Stochastic Environmental Research and Risk Assessment - This paper explores and combines implicit stochastic optimization (ISO) with copula functions to simulate long-term operating policies for a...  相似文献   

Geochemistry of diffuse low-temperature hydrothermal fluids in the North Fiji basin     

Andrea Koschinsky  Richard SeifertPeter Halbach  Michael BauSabine Brasse  Leandro M de CarvalhoNuno M Fonseca 《Geochimica et cosmochimica acta》2002,66(8):1409-1427

Low-temperature (<13°C) diffuse hydrothermal fluids were sampled directly at the seafloor with a specially designed Hydro Bottom Station in the North Fiji Basin and analyzed for gases, major and minor elements, and a large number of trace metals. The fluids were significantly enriched in CO₂, Si, Li, Rb, Cs, Ba, Mn, and several trace metals compared to ambient seawater, had high CH₄ and H₂S concentrations, and had a slightly decreased salinity. Calculated end-member concentrations of the low-temperature fluids show a strong similarity to the neighboring hot vents, implying that the diffuse fluids are hot vent waters diluted by seawater. According to the chemical composition, the sampled fluids derive from vapor-phase fluids produced by subseafloor boiling and phase separation. Compared to hot vents from other regions, Mn, Fe, and other trace metal concentrations are low. Subsurface metal sulfide precipitation during cooling and dilution with seawater has further decreased the dissolved metal contents of the diffuse fluids, thus creating a very favorable environment for the hydrothermal fauna, as indicated by a very low Fe/H₂S ratio. Therefore, the fluids support high bioproductivity but no hydrothermal mineral precipitation. The emanation of the condensed vapor phase appears to have been stable during the past 10 years; however, the occurrence of metal sulfide particles in some fluid and sediment samples and small areas of dead fauna indicate that the hydrothermal system may be evolving toward the emanation of the stored brine phase.  相似文献   

Time domain scattering of acoustic plane waves by vertical faults     

Edson E. S. Sampaio  Mikhail M. Popov 《Pure and Applied Geophysics》1996,148(1-2):95-112

Acoustic plane wave scattering at a vertical fault structure represents the simplest two-dimensional model of geophysical exploration that can be investigated by analytical techniques. The exact and complete solution, in the time domain, for the scattering of the pressure field of an acoustic plane wave normally incident on a vertical fault structure is determined adapting previous results given for the frequency domain. The wave form of the pressure field of the incident plane wave is expressed by a causal time function that decays exponentially with time at every point above the fault (z<0). The zero-order term of the scattered pressure field has been computed above the fault. This zero-order term consists of an inverse Fourier transform which reduces to a closed expression forx=0, and contains an integral of a Hankel function forx#0. The high frequency part of the inverse Fourier transform forx#0 is computed employing asymptotic expressions for the Hankel function. The integral of the asymptotic expression of the Hankel function reduces to: (i) a Fresnel integral which contains a plane wave term for |x||z|; and (ii) a stationary point plane wave term plus an upper limit term for |x|=O(|z|). For the latter case the plane wave term cancels, leaving a cylindrical wave emanated from the edge of the fault. The wave front is well defined in shape, in phase and in amplitude. The amplitude of the scattered field is discontinuous atx=0, presents a jump and is well defined for |x| small and is rather smooth for |x| large.  相似文献   

Carbon Sequestration and Turnover in Semiarid Savannas and Dry Forest   总被引：5，自引：1，他引：4  

H. Tiessen  C. Feller  E.V.S.B. Sampaio  P. Garin 《Climatic change》1998,40(1):105-117

Data on carbon and biomass budgets under different land use in tropical savannas and some dry forests are reviewed. Global data show wide ranges of biomass carbon stocks (20-150 Mg C ha-1), net primary production (2-15 Mg C ha-1y-1) and litter production (2-10 Mg C ha-1y-1) for the semiarid tropics. Although ranges for soil carbon are also wide, an average figure for the top 20 cm is probably 10 g C kg-1, or about 25 Mg C ha-1. In order to arrive at a better understanding of C budgets and their controls, two regional reviews are presented for NE Brazil and W. Africa.In NE Brazil approximately 40% of the lands have "near-climax" native vegetation. Less than 10% of the area is planted annually, but about 3-4 times that area is affected by shifting cultivation which has an average cycle of 5 y arable use followed by 20 y or more recovery. Standing biomass of native caatinga shows nearly the full global range with 2-50 Mg C ha-1. Litter fall around 1-2 Mg C ha-1y-1 is partly decomposed and partly consumed by animals, resulting in low average soil C levels near 8 g kg-1, or 20 Mg C ha-1. Under cultivation, C sequestration is decreased, and soils lose approximately half their C stocks before being abandoned.In W. Africa between 50-70% of the land is under a management regime with minimal C returns to the soils. Overgrazing and over-exploitation for fuel wood has resulted in land degradation. Short fallow periods on cultivated lands have caused serious declines in soil C stocks. Both C sequestration and stocks are therefore lower in W. Africa than in NE Brazil.Improvements in the C sequestration in these semi arid regions depend on an increase in crop production under suitable rotations, improved fallow and animal husbandry, and a limitation on biomnass burning. Use of fertilizer is required for improved productivities but socioeconomic constraints largely prevent such improvements, resulting in a very limited scope for changes in soil C management.  相似文献   

Magnetotelluric profiling of vertical conductors     

E. S. Sampaio 《Pure and Applied Geophysics》1976,114(6):1009-1020

The presence of lateral contrasts of electrical conductivity modifies the original pattern of electromagnetic fields radiated from remote sources. A magnetic transverse plane wave field, interacting with a vertical conductive and outcropping dike placed between two quarter-spaces of unequal electrical conductivities, creates an anomalous vertical component of the magnetic field. This anomalous field has been analysed by computation, and drafting of master curves. Two case histories are presented to illustrate the application and the effectiveness of the solution. It is concluded that: (i) the response is higher for intermediate values of the conducting body induction number; (ii) the curves can be used for the inter-pretation of magnetotelluric, AFMAG, and VLF exploration data; (iii) it is necessary to develop solutions taking into account the vertical as well as the lateral variation of conductivity.  相似文献   

Seismic performance and damage evaluation of a reinforced concrete frame with hysteretic dampers through shake‐table tests          下载免费PDF全文

Amadeo Benavent‐Climent  Leandro Morillas  David Escolano‐Margarit 《地震工程与结构动力学》2014,43(15):2399-2417

Passive energy dissipation devices are increasingly implemented in frame structures to improve their performance under seismic loading. Most guidelines for designing this type of system retain the requirements applicable to frames without dampers, and this hinders taking full advantage of the benefits of implementing dampers. Further, assessing the extent of damage suffered by the frame and by the dampers for different levels of seismic hazard is of paramount importance in the framework of performance‐based design. This paper presents an experimental investigation whose objectives are to provide empirical data on the response of reinforced concrete (RC) frames equipped with hysteretic dampers (dynamic response and damage) and to evaluate the need for the frame to form a strong column‐weak beam mechanism and dissipate large amounts of plastic strain energy. To this end, shake‐table tests were conducted on a 2/5‐scale RC frame with hysteretic dampers. The frame was designed only for gravitational loads. The dampers provided lateral strength and stiffness, respectively, three and 12 times greater than those of the frame. The test structure was subjected to a sequence of seismic simulations that represented different levels of seismic hazard. The RC frame showed a performance level of ‘immediate occupancy’, with maximum rotation demands below 20% of the ultimate capacity. The dampers dissipated most of the energy input by the earthquake. It is shown that combining hysteretic dampers with flexible reinforced concrete frames leads to structures with improved seismic performance and that requirements of conventional RC frames (without dampers) can be relieved. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Comparative study of urban development and groundwater condition in coastal areas of Buenos Aires,Argentina     

Leandro Rodrigues Capítulo  Silvina C. Carretero  Eduardo E. Kruse 《Hydrogeology Journal》2017,25(5):1407-1422

The geomorphological evolution of a sand-dune barrier in Buenos Aires, Argentina, is analyzed as a factor regulating the fresh groundwater reserves available. The impact of geomorphological evolution and the consequences for the social and economic development of two coastal areas are assessed. This is one of the most important tourist destinations in the country; for study purposes, it was divided into a northern sector and a southern sector. In the southern sector, the exploitable groundwater is associated with the Holocene and upper Pleistocene geomorphological evolution, which generated three interrelated aquifer units, constituting a system whose useful thickness reaches at least 45 m. In contrast, the northern sector is restricted to two Holocene aquifer units, whose total thickness is on the order of 12 m. The morphological characteristics and the occurrence of the largest fresh groundwater reserves in the southern sector are indicators of better conditions for economic growth, which is mainly reflected on the expansion of real estate ventures. The relationships of transmissivity vs area of real estate ventures (Arev), and total water consumption vs Arev, are indicators for the sustainable management of the water resources. The approach chosen may be used by decision makers in other regions to assess the feasibility of future tourism projects on the basis of the availability of water resources associated with geomorphological features.  相似文献   

Characterization of a landslide-triggered debris flow at a rainforest-covered mountain region in Brazil     

Cabral  Victor Carvalho  Reis  Fábio Augusto Gomes Vieira  D’Affonseca  Fernando Mazo  Lucía  Ana  dos Santos Corrêa  Claudia Vanessa  Veloso  Vinicius  Gramani  Marcelo Fischer  Ogura  Agostinho Tadashi  Lazaretti  Andrea Fregolente  Vemado  Felipe  Pereira Filho  Augusto José  dos Santos  Claudia Cristina  Lopes  Eymar Silva Sampaio  Rabaco  Lis Maria Reoni  do Carmo Giordano  Lucilia  Zarfl  Christiane 《Natural Hazards》2021,108(3):3021-3043

Natural Hazards - Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies,...  相似文献   

Capability of LISEM to estimate flood hydrographs in a watershed with predominance of long-duration rainfall events     

Vargas  Marcelle Martins  Beskow  Samuel  de Mello  Carlos Rogério  de Moura  Maíra Martim  Nunes  Maria Cândida Moitinho  Faria  Lessandro Coll  Aquino  Leandro Sanzi 《Natural Hazards》2021,109(1):593-614

Natural Hazards - Process-based hydrological models are of great importance to understand hydrological processes and support decision making. The LImburg Soil Erosion Model (LISEM) requires...  相似文献   

The Continuum Voronoi Block Model for simulation of fracture process in hard rocks     

Erick Rgenes  Mrcio Muniz de Farias  Leandro Lima Rasmussen 《国际地质力学数值与分析法杂志》2022,46(1):89-112

In this paper, a numerical model is presented to represent the fracture process in hard rocks based on a pseudo-discontinuum method called the Continuum Voronoi Block Model (CVBM). To validate this tool, numerical models for one Brazilian test, one unconfined compression test, and multiple triaxial compression tests with different confining stress were calibrated to match laboratory test results for Creighton granite. The model proved robust and matched the following macro-properties: crack initiation (CI) stress, (CD) stress, peak strength, tensile strength, Young's Modulus, and Poisson's ratio. The calibrated model served as a basis for a sensitivity study to analyze how micro-properties influence the rock's macroscopic responses. From the sensitivity study, a calibration methodology was proposed, which shall facilitate the use of the CVBM in future works.  相似文献