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71.
72.
Massimo Fracassini Paola Maggi Laura E. Pasinetti 《Astrophysics and Space Science》1986,128(2):363-368
The results of research on pairs of PSR which were possibly components of disrupted binaries, seem to advance further arguments in favour of the idea, suggested by some authors, that most of PSR were formed in binary systems. 相似文献
73.
Massimo Marro Pietro Salizzoni Lionel Soulhac Massimo Cassiani 《Boundary-Layer Meteorology》2018,167(3):349-369
We analyze the reliability of the Lagrangian stochastic micromixing method in predicting higher-order statistics of the passive scalar concentration induced by an elevated source (of varying diameter) placed in a turbulent boundary layer. To that purpose we analyze two different modelling approaches by testing their results against the wind-tunnel measurements discussed in Part I (Nironi et al., Boundary-Layer Meteorology, 2015, Vol. 156, 415–446). The first is a probability density function (PDF) micromixing model that simulates the effects of the molecular diffusivity on the concentration fluctuations by taking into account the background particles. The second is a new model, named VP\(\varGamma \), conceived in order to minimize the computational costs. This is based on the volumetric particle approach providing estimates of the first two concentration moments with no need for the simulation of the background particles. In this second approach, higher-order moments are computed based on the estimates of these two moments and under the assumption that the concentration PDF is a Gamma distribution. The comparisons concern the spatial distribution of the first four moments of the concentration and the evolution of the PDF along the plume centreline. The novelty of this work is twofold: (i) we perform a systematic comparison of the results of micro-mixing Lagrangian models against experiments providing profiles of the first four moments of the concentration within an inhomogeneous and anisotropic turbulent flow, and (ii) we show the reliability of the VP\(\varGamma \) model as an operational tool for the prediction of the PDF of the concentration. 相似文献
74.
Simone Simeone Emanuela Molinaroli Alessandro Conforti Giovanni De Falco 《Climatic change》2018,150(3-4):227-242
The production of sediments by carbonate-producing ecosystems is an important input for beach sediment budgets in coastal areas where no terrigenous input occurs. Calcifying organisms are a major source of bioclastic carbonate sediment for coastal systems. Increased levels of CO2 in the atmosphere are leading to an increase in the partial pressure of CO2 on ocean seawater, causing ocean acidification (OA), with direct consequences for the pH of ocean waters. Most studies of OA focus on its impact on marine ecosystems. The impact of OA on carbonate-producing ecosystems could be to reduce the amount of sediments supplied to temperate coastal systems. The aim of this study was to quantify the effect of the predicted OA on the long-term sediment budget of a temperate Mediterranean mixed carbonate beach and dune system. Based on projections of OA we estimated a fall of about 31% in the present bioclastic carbonate sediment deposition rate, with the biggest decreases seen in the dunes (? 46%). OA is also expected to affect the carbonate sediment reservoirs, increasing the dissolution of CaCO3and causing net sediment loss from the system (~ 50,000 t century?1). In the long-term, OA could also play a primary role in the response of these systems to sea-level rise. Indeed, the reduction in the quantity of carbonate sediments provided to the system may affect the speed with which the system is able to adapt to sea-level rise, by increasing wave run-up, and may promote erosion of dunes and subaerial beaches. 相似文献
75.
An improved method for delineating source protection zones for karst springs based on analysis of recession curve data 总被引:1,自引:1,他引:0
Massimo V. Civita 《Hydrogeology Journal》2008,16(5):855-869
A standard method for delineating source protection zones, particularly for karst and carbonate springs, has been improved. The method, based on recession curve analysis, defines four vulnerability scenarios with an evaluation of the appropriate dimensions of the protection areas, accommodating situations where field-test data are not available. The new approach makes it easier to separate the components of the spring discharge hydrograph. The objective is to achieve simplification, and an effective, more rigorous, procedure in the determination of the parameters used by Mangin’s model—Mangin A (1975) Contribution a l’étude hydrodynamique des aquifères karstiques-Troisieme partie: Constitution et fonctionnement des aquifères karstiques (Contribution to the hydrodynamic study of karst aquifers, part 3: formation and work of karst aquifers). Ann Speleol 30(1):21–124. The original procedure, plus the lack of sufficient data, was open to subjective interpretation. With the aid of modern technology, a very large quantity of data is now available and it is necessary to process it using denoise type computer-based filters before passing to interpretation. Working with discharge data series, a statistical approach is proposed to give an analytical solution for determining the values of fundamental parameters of the recession curve model. The new procedure is defined and compared with the original methodology. The new approach has been tested and applied to a number of karst springs in Italy. A case history for a spring located in the Piedmont region of the Maritime Alps, is presented. The proposed new procedure can be utilised to mark the limits of the protection zones of tapped groundwater supplied for potable use, as required by European and local legislation. 相似文献
76.
This article explores the impacts of floods on the economy, environment, and society and tries to clarify the rural community’s
coping mechanism to flood disasters in Central Viet Nam. It focuses on the social aspects of flood risk perception that shapes
the responses to floods. The research findings revealed that flooding is an essential element for a coastal population, whose
livelihood depend on productive functions of cyclical floods. The findings also revealed that floods, causing losses and damages,
often inhibited economic development. The surveyed communities appeared to have evolved coping mechanisms to reduce the negative
impacts of the floods, yet these coping mechanisms are under pressure due to environmental degradation. Integrated flood risk
management is considered as a suitable paradigm for coping with flood disasters.
相似文献
Phong TranEmail: |
77.
Comment on Non‐unique stratal geometries: implications for sequence stratigraphic interpretations,by: P.M. Burgess and G.D. Prince,Basin Research (2015) 27, 351–365 下载免费PDF全文
The non‐unique variability highlighted by Burgess & Prince (Basin Res. 2015, 27 , 351) (i.e. the origin and timing of maximum flooding surfaces, maximum regressive surfaces and subaerial unconformities; the process of topset aggradation in relation with the various types of shoreline trajectory; and the multiple controls that may affect the progradation and retrogradation of a shoreline) is irrelevant to the workflow of sequence stratigraphy. What is relevant is the observation of the unique stratal geometries that are diagnostic to the definition of all units and surfaces of sequence stratigraphy. In downstream‐controlled settings, these unique stratal stacking patterns relate to the forced regressive, normal regressive and transgressive shoreline trajectories. Multiple controls interplay during the formation of each type of stacking pattern, including accommodation, sediment supply and the energy of the sediment‐transport agents. This interplay explains the non‐unique variability, but does not change the unique criteria that afford a consistent application of sequence stratigraphy. Failure to rationalize the non‐unique variability within the context of unique stratal geometries is counterproductive, and obscures the simple workflow of sequence stratigraphy. 相似文献
78.
卫星遥感结合地面资料对区域表面动量粗糙度的估算 总被引:10,自引:0,他引:10
利用地面湍流观测资料估算了黑河实验区几个典型下垫面的局地地表动量粗糙度,与卫星观测Landsat TM资料相结合得到了由标准化差值植被指数(NDVI)计算地表动量粗糙度的经验关系式,进而估算了实验区夏季和近冬季的地表粗糙度的区域分布,并对所得关系式进行了合理性检验。 相似文献
79.
Francesco Di Benedetto Ilaria Bencistà Francesco D’Acapito Silvia Frizzera Andrea Caneschi Massimo Innocenti Alessandro Lavacchi Giordano Montegrossi Werner Oberhauser Maurizio Romanelli Herbert Dittrich Luca A. Pardi Gerold Tippelt Georg Amthauer 《Physics and Chemistry of Minerals》2016,43(8):535-544
The successful synthesis of nanoparticles of Fe-bearing kuramite, (Cu,Fe)3SnS4, is reported in this study. Nanocrystalline powders were obtained through a mild, environmentally friendly and scalable solvothermal approach, in a single run. The sample was the object of a multidisciplinary investigation, including X-ray diffraction and absorption, scanning electron microscopy and microanalysis, electron paramagnetic resonance, diffuse reflectance and Mössbauer spectroscopy as well as SQUID magnetometry. The nanoparticles consist of pure Fe-bearing kuramite, exhibiting tetragonal structure. The valence state of the metal cations was assessed to be Cu+, Sn4+ and Fe3+. The material presents a band gap value of 1.6 eV, which is fully compatible with solar cell applications. The uptake of Fe by nanokuramite opens a compositional field where the physical properties can be tuned. We thus foster the application of Fe-bearing nanokuramite for photovoltaics and energy storage purposes. 相似文献