Density structure of the giant HII region NGC 2363     

Enrique Pérez  Rosa González Delgado  José M. Vílchez 《Astrophysics and Space Science》2001,277(1):83-86

We perform a detailed measurement of the electron density along two slit position angles in the bright, low metallicity extragalactic HII region NGC 2363. A comparison of the density structures obtained with the two independent diagnostics given by [AIV]4711/4740 and [SII]6716/6731, show that they present both different absolute values and different radial dependencies, with the [AIV] densities reaching up to 1000 cm^-3. We explore the implications for the computation of the He abundance.  相似文献   

On the initial orientation of emerging active regions     

J. I. García De La Rosa 《Solar physics》1986,103(2):249-257

The initial orientation of 74 active regions is measured in high resolution pictures. As previous works by the author (García de la Rosa, 1984) suggest a different behaviour between large and small active regions, the sample has been divided into those two classes, whose dividing line is roughly set at 5 × 10²¹ Mx in the magnetic flux. It is observed that only the large regions tend to display the correct inclination (p-part at lower latitude). Their evolution towards a more parallel inclination to the equator is also observed.The first finding is interpreted in terms of the primary nature of the large ARs which are supposed to be directly linked to the basic mechanism of solar activity. The evolution is interpreted as a reaction of the lower layers of the tube to the tilt introduced by the Coriolis effect.  相似文献   

Pattern and annual rates of Scrobicularia plana mercury bioaccumulation in a human induced mercury gradient (Ria de Aveiro, Portugal)     

J.P. Coelho  M. Rosa  E. Pereira  A. Duarte  M.A. Pardal 《Estuarine, Coastal and Shelf Science》2006,69(3-4):629

Due to the lack of knowledge regarding annual bioaccumulation rates in estuarine and marine fauna, the main aim of this work was to study the annual mercury bioaccumulation in the well-documented bivalve species Scrobicularia plana along a human induced mercury gradient in the Ria de Aveiro coastal lagoon (Portugal) and in a nearby, non-polluted system (Mondego estuary), parallel to the risks associated with its consumption by humans.Minimum total mercury concentration was as low as 0.019 mg kg⁻¹ (wwt) in 4+ year old organisms in the reference site, where a significant negative correlation (p < 0.05) was found between total mercury concentrations and size, resulting in negative bioaccumulation rates (detoxification). On the other hand, values reached 1.8 mg kg⁻¹ (wwt) in 3+ year old bivalves from the most contaminated area, where a strong positive correlation with size was found (p < 0.01) and annual bioaccumulation rates were as high as 0.25 mg kg⁻¹ yr⁻¹. Annual bioaccumulation rates were highly correlated with suspended particulate matter mercury concentrations. Even though the levels of organic mercury contents increased parallel to the contamination gradient, at each sampling station, no increment was found with age, which corresponded to a decrease in organic mercury percentage with age.In terms of ecological management and public health, the ratio of 0.01 consistently found between Scrobicularia plana annual mercury accumulation rates and SPM mercury levels for most sites may permit to roughly estimate S. plana contamination of commercial sized individuals (>2.5 cm) and, if verified and confirmed in other systems, be used as a simple management tool.  相似文献   

Rigorous Analysis of Available Data from Cerro Prieto and Las Tres Virgenes Geothermal Fields with Calculations for Expanded Electricity Generation     

Rosa María Prol-Ledesma  Claudia Arango-Galván  Marco-Antonio Torres-Vera 《Natural Resources Research》2016,25(4):445-458

Changes in legislation have opened the Mexican geothermal resources for exploitation to private companies; therefore the evaluation of the known geothermal areas has a high priority to plan further exploitation and possibly the expansion of the well fields. The calculation of the remaining productivity of geothermal fields currently in exploitation can be achieved with less uncertainty using the parameters obtained from production and injection wells, as well as the production efficiency of the installed plants. No information about previous volumetric evaluation is available for the fields presently being exploited, and there is the possibility that they may support an increase in their energy output or extend further their production life. The most widely used calculation technique is the USGS volumetric method that requires the knowledge of parameters that can be measured only after exploitation started. Heat in place-volumetric evaluation was undertaken for two fields in Mexico: Cerro Prieto and the Las Tres Vírgenes geothermal fields, using all information obtained by exploration surveys and exploitation drilling. The obtained values allow planning a possible expansion of the fields based on their estimated mean potential output that is 1397 MWe for Cerro Prieto and 48 MWe for Las Tres Vírgenes compared to the presently installed capacity of 580 MWe.  相似文献   

Landslide risk perception and communication for disaster risk management in mountain areas of developing countries: a Mexican foretaste     

Irasema Alcántara-Ayala  Ana Rosa Moreno 《山地科学学报》2016,13(12):2079-2093

The increasing impact of disasters at local,national,regional and global scales in recent decades has provided enough evidence to urgently direct attention towards the necessity of disaster risk reduction and management,and this requires knowledge.Knowledge without communication is barren,and to communicate the risk of disaster it is necessary to understand the perception of the people at risk.In particular,this paper deals with the necessity to delineate strategies of risk communication in pursuance of risk knowledge as a core of disaster risk reduction and management,especially in mountain areas of developing countries.To portray this issue,an analysis of landslide risk perception in terms of experience,landslide risk awareness,exposure,preparedness,and risk communication and trust was undertaken in the municipality of Teziutlán,Puebla,Mexico,an area that has been affected for several decades by episodes of mass movement.Analysis of the responses to a risk perception questionnaire has offered valuable insights in terms of the information and knowledge most required by the people living in the area of interest,in order to devise a realistic and functional strategy to communicate the risk of a landslide disaster.This includes better understanding of controlling factorsand drivers of this risk,and the establishment of potential trusted sources of risk communication.Beyond considering practical matters of risk assessment and management,risk perception and communication can increase the resilience of vulnerable people,and can enhance capacity building for present and future generations.  相似文献   

Multi-frequency satellite radar imaging of cultural heritage: the case studies of the Yumen Frontier Pass and Niya ruins in the Western Regions of the Silk Road Corridor     

Fulong Chen  Nicola Masini  Jie Liu  Jiangbin You  Rosa Lasaponara 《International Journal of Digital Earth》2016,9(12):1224-1241

Synthetic Aperture Radar (SAR) remote sensing is increasingly favoured in archaeological applications. However, the effectiveness of this technology for archaeological prospection has so far not been fully assessed. In this study, an integrated single-date and multi-temporal SAR data-processing chain was proposed to sharpen archaeological signs and hence their detection and monitoring. In total, 14 scenes of X-band Cosmo-SkyMed, C-band Sentinel-1 and L-band PALSAR data covering the Western Regions of the Silk Road Corridor in China were employed for two important archaeological sites including the Yumen Frontier Pass with emerging archaeological traces and Niya ruins with subsurface remains. The results pointed out that single-date satellite radar data were useful for the identification of subsurface traces buried under desert in the landscape-scale, whereas for the identification of emerging monuments, Sentinel-1 was limited by its lower spatial resolution compared to TerraSAR and PALSAR data. Multi-date products, such as interferometric coherence, the averaged radar signatures and RGB multi-temporal composites, were effective to sharpen archaeological traces as well as for change detection in Yumen Frontier Pass. This study presents a pilot assessment of satellite SAR data for the analysis and monitoring of archaeological features in the predominantly arid-sandy environmental characteristic of investigated sites.  相似文献   

Could working less reduce pressures on the environment? A cross-national panel analysis of OECD countries, 1970–2007     

Kyle W. Knight  Eugene A. Rosa  Juliet B. Schor 《Global Environmental Change》2013,23(4):691-700

Many scholars and activists are now advocating a program of economic degrowth for developed countries in order to mitigate demands on the global environment. An increasingly prominent idea is that developed countries could achieve slower or zero economic growth in a socially sustainable way by reducing working hours. Research suggests that reduced working hours could contribute to sustainability by decreasing the scale of economic output and the environmental intensity of consumption patterns. Here, we investigate the effect of working hours on three environmental indicators: ecological footprint, carbon footprint, and carbon dioxide emissions. Using data for 1970–2007, our panel analysis of 29 high-income OECD countries indicates that working hours are significantly associated with greater environmental pressures and thus may be an attractive target for policies promoting environmental sustainability.  相似文献   

Free vibrations of simply supported double plate on two models of elastic soils     

M. A. De Rosa  M. Lippiello 《国际地质力学数值与分析法杂志》2009,33(3):331-353

In this paper the free vibrations of simply supported rectangular plates, resting on two different models of soils, are considered. The first model called Hetényi, by the name of the deviser, assumes a continuous plate, embedded in a Winkler‐type soil to realize the foundation partial continuity. The upper plate rests on a multiple layer characterized by a Winkler‐type soil, a continuous plate and another Winkler‐type soil in sequence. The two Winkler‐type soils have different modules. In the second model, the plate will be embedded in two layers of soils, whose behavior is similar to that of the Pasternak–Kerr‐type soil. The two models have been already used for the study of the double beam system. The free motions, in both cases, are described by a homogeneous set of partial differential equations, based on Kirchhoff–Love theory. Next, the homogeneous equations of motion are solved by using the classical Navier method. The free frequencies and associated vibration mode shapes of double plate system are found and numerical examples are illustrated to compare the two models. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Fast multipole displacement discontinuity method (FM‐DDM) for geomechanics reservoir simulations          下载免费PDF全文

Alexander Verde  Ahmad Ghassemi 《国际地质力学数值与分析法杂志》2015,39(18):1953-1974

The displacement discontinuity method (DDM) is frequently used in geothermal and petroleum applications for modeling the behavior of fractures in linear‐elastic rocks. The DDM requires O(N²) memory and O(N³) floating point operations (where N is the number of unknowns) to construct the coefficient matrix and solve the linear system of equations by direct methods. Therefore, the conventional implementation of the DDM is not computationally efficient for very large systems of cracks, often limiting its application to small‐scale problems. This work presents an approach for solving large‐scale fracture problems using the fast multipole method (FMM). The approach uses both the DDM and a kernel‐independent version of the FMM along with a preconditioned generalized minimal residual algorithm to accelerate the solution of linear systems of equations using desktop computers. Using the fundamental solutions for constant displacement discontinuity in a two‐dimensional elastic medium, several numerical examples involving fracture networks representing fractured reservoirs are treated. Numerical results show good agreement with analytical solutions and demonstrate the efficiency of the FMM implementation of the DDM for large‐scale simulations. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Geology, ore deposits and hydrothermal venting in Bahía Concepción, Baja California Sur, Mexico     

Antoni  Camprubí  Carles  Canet  Augusto A.  Rodríguez-Díaz  Rosa M.  Prol-Ledesma  David  Blanco-Florido  Ruth E.  Villanueva  Abigail  López-Sánchez 《Island Arc》2008,17(1):6-25

Abstract Bahía Concepción is located in the eastern coast of the Baja California peninsula and it is shaped by northwestern–southeastern normal faults. These are associated with a 12–6 Ma rifting episode, although some have been reactivated since the Pliocene. The most abundant rocks correspond to the arc related Comondú Group, Oligocene to Miocene, which forms a mainly calc‐alkaline volcanic and volcaniclastic sequence. There are less extensive outcrops of sedimentary rocks, lava flows, domes and pyroclastic rocks of Pliocene to Quaternary ages. The Neogene volcanism in the area indicates a shift from a subduction regime to an intraplate volcanism related to continental extension and the opening of an oceanic basin. The Bahía Concepción area contains numerous Mn ore deposits, being the biggest at El Gavilán and Guadalupe. The Mn deposits occur as veins, breccias and stockworks, and are composed by Mn oxides (pyrolusite, coronadite, romanechite), dolomite, quartz and barite. The deposits are hosted in volcanic rocks of the Comondú Group and, locally, in Pliocene sedimentary rocks. Thus, the Mn deposits formed between the Middle Miocene and the Pliocene. The mineralized structures are associated with Miocene northwestern–southeastern fault systems, which are analogous to those associated with the Cu‐Co‐Zn‐Mn deposits of El Boleo. The Bahía Concepción area also bears subaerial and submarine hot springs, which are associated with the same fault systems and host rocks. The submarine and subaerial geothermal manifestations south of the bay are possibly related with recent volcanism. The geothermal manifestations within the bay are intertidal hot springs and shallow submarine diffuse venting areas. Around the submarine vents (5–15 m deep, 87°C), Fe‐oxyhydroxide crusts with pyrite and cinnabar precipitate. In the intertidal vents (62°C), aggregates of opal, calcite, barite and Ba‐rich Mn oxides occur covered by silica‐carbonate stromatolitic sinters. Some 10–30 cm thick crustiform veins formed by chalcedony, calcite and barite are also found close to the vents. The hydrothermal fluids exhibit mixed isotopic compositions between δ¹⁸O‐enriched meteoric and local marine water. The precipitation of Ba‐rich Mn oxides around the vent sites could be an active analog for the processes that produced Miocene to Pliocene hydrothermal Mn‐deposits.  相似文献