Preface     

Bernhard M. Haisch  Marcello Rodonò 《Solar physics》1989,121(1-2):1-2

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Reactive Transport Modeling of ZVI Column Experiments for Nickel Remediation     

Stefania Bilardi  Richard T. Amos  David W. Blowes  Paolo S. Calabrò  Nicola Moraci 《Ground Water Monitoring & Remediation》2013,33(1):97-104

MIN3P, a multicomponent reactive transport model for variably saturated porous media, is used to simulate the outputs of column tests carried out using zero valent iron (ZVI) for nickel contaminated groundwater remediation. The objective of this study is to investigate the main chemical reactions involved in contaminant removal and the main causes of the reactivity decline of ZVI over time. According to the results of the model the major causes of ZVI reactivity loss is identified in the mineral precipitation of α‐FeOOH on iron surface that probably caused ZVI passivation and led to a decline of the electron transfer rate. An existing empirical relationship between mineral precipitation and the reactivity loss of ZVI, included in the model, reproduced the changes in nickel removal observed during different laboratory column tests.  相似文献   

Three-Dimensional Properties of Coronal Mass Ejections from STEREO/SECCHI Observations     

E. Bosman  V. Bothmer  G. Nisticò  A. Vourlidas  R. A. Howard  J. A. Davies 《Solar physics》2012,281(1):167-185

We identify 565 coronal mass ejections (CMEs) between January 2007 and December 2010 in observations from the twin STEREO/SECCHI/COR2 coronagraphs aboard the STEREO mission. Our list is in full agreement with the corresponding SOHO/LASCO CME Catalog ( http://cdaw.gsfc.nasa.gov/CME_list/ ) for events with angular widths of 45^° and up. The monthly event rates behave similarly to sunspot rates showing a three- to fourfold rise between September 2009 and March 2010. We select 51 events with well-defined white-light structure and model them as three-dimensional (3D) flux ropes using a forward-modeling technique developed by Thernisien, Howard and Vourlidas (Astrophys. J. 652, 763??C?773, 2006). We derive their 3D properties and identify their source regions. We find that the majority of the CME flux ropes (82?%) lie within 30^° of the solar equator. Also, 82?% of the events are displaced from their source region, to a lower latitude, by 25^° or less. These findings provide strong support for the deflection of CMEs towards the solar equator reported in earlier observations, e.g. by Cremades and Bothmer (Astron. Astrophys. 422, 307??C?322, 2004).  相似文献   

Predictive potential of Perzyna viscoplastic modelling for granular geomaterials     

Maria Lazari  Lorenzo Sanavia  Claudio di Prisco  Federico Pisanò 《国际地质力学数值与分析法杂志》2019,43(2):544-567

This paper reappraises Perzyna-type viscoplasticity for the constitutive modelling of granular geomaterials, with emphasis on the simulation of rate/time effects of different magnitude. An existing elasto-plastic model for sands is first recast into a Perzyna viscoplastic formulation and then calibrated/validated against laboratory test results on Hostun sand from the literature. Notable model features include (1) enhanced definition of the viscous nucleus function and (2) void ratio dependence of stiffness and viscous parameters, to model the pycnotropic behaviour of granular materials with a single set of parameters, uniquely identified against standard creep and triaxial test results. The comparison between experimental data and numerical simulations points out the predicative capability of the developed model and the complexity of defining a unique viscous nucleus function to capture sand behaviour under different loading/initial/boundary and drainage conditions. It is concluded that the unified viscoplastic simulation of both drained and undrained response is particularly challenging within Perzyna's framework and opens to future research in the area. The discussion presented is relevant, for instance, to the simulation of multiphase strain localisation phenomena, such as those associated to slope stability problems in variably saturated soils.  相似文献   

On the rheological characterisation of liquefied sands through the dam-breaking test     

Gabriele Della Vecchia  Massimiliano Cremonesi  Federico Pisanò 《国际地质力学数值与分析法杂志》2019,43(7):1410-1425

This paper concerns the rheological characterisation of liquefied sands as non-Newtonian Bingham fluids. For this purpose, dam-breaking laboratory tests are often executed and interpreted, offering a viable option to identify the properties of fluidised water-soil mixtures. However, limited attention has been devoted so far to clarify what variables and measurements would allow unambiguous calibration of Bingham parameters, namely, the viscosity η and the yield stress τ_y. The numerical results of parametric studies based on the particle finite element method (PFEM) are critically inspected to gain deeper insight into the problem. First, it is confirmed that multiple η − τ_y pairs may reproduce the same experimental evidence when formed by only one measurement—usually, the post–dam-breaking displacement of the bottom toe (tip) of the liquefied mass. Then, two alternative procedures are proposed for unambiguous identification of both η and τ_y: one is based on monitoring the evolving aspect ratio of the fluid mass during free, gravity-driven flow; the other relies on a slightly different dam-breaking test, also including impact against a rigid obstacle. In particular, the latter approach reduces the relevant duration of the test, reducing the possible influence of reconsolidation effects on the calibration of rheological parameters.  相似文献   

High‐P tectono‐metamorphic evolution of mylonites from the Variscan basement of the Northern Apennines,Italy          下载免费PDF全文

Deborah Lo Pò  Roberto Braga  Hans‐Joachim Massonne  Giancarlo Molli  Alessandra Montanini  Giuseppe M. Bargossi 《Journal of Metamorphic Geology》2018,36(1):23-39

Strain localization within shear zones may partially erase the rock fabric and the metamorphic assemblage(s) that had developed before the mylonitic event. In poly‐deformed basements, the loss of information on pre‐kinematic phases of mylonites hinders large‐scale correlations based on tectono‐metamorphic data. In this study, devoted to a relict unit of Variscan basement reworked within the nappe stack of the Northern Apennines (Italy), we investigate the possibility to reconstruct a complete pressure (P)–temperature (T)–deformation (D) path of mylonitic micaschist and amphibolite by integrating microstructural analysis, mineral chemistry and thermodynamic modelling. The micaschist is characterized by a mylonitic fabric with fine‐grained K‐white mica and chlorite enveloping mica‐fishes, quartz, and garnet pseudomorphs. Potassic white mica shows Mg‐rich cores and Mg‐poor rims. The amphibolite contains green amphibole+plagioclase+garnet+quartz+ilmenite defining S₁ with a superposed mylonitic fabric localized in decimetre‐ to centimetre‐scale shear zones. Garnet is surrounded by an amphibole+plagioclase corona. Phase diagram calculations provide P–T constraints that are linked to the reconstructed metamorphic‐deformational stages. For the first time an early high‐P stage at >11 kbar and 510°C was constrained, followed by a temperature peak at 550–590°C and 9–10 kbar and a retrograde stage (<475°C, <7 kbar), during which ductile shear zones developed. The inferred clockwise P–T–D path was most likely related to crustal thickening by continent‐continent collision during the Variscan orogeny. A comparison of this P–T–D path with those of other Variscan basement occurrences in the Northern Apennines revealed significant differences. Conversely, a correlation between the tectono‐metamorphic evolution of the Variscan basement at Cerreto pass, NE Sardinia and Ligurian Alps was established.  相似文献   

Authors' Reply     

O. Paladino  Marco Massabò 《Ground water》2012,50(2):178-179

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GTE: a new software for gravitational terrain effect computation: theory and performances     

D. Sampietro  M. Capponi  D. Triglione  A. H. Mansi  P. Marchetti  F. Sansò 《Pure and Applied Geophysics》2016,173(7):2435-2453

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Characteristics of EUV Coronal Jets Observed with STEREO/SECCHI     

G. Nisticò  V. Bothmer  S. Patsourakos  G. Zimbardo 《Solar physics》2009,259(1-2):87-108

In this paper we present the first comprehensive statistical study of EUV coronal jets observed with the SECCHI (Sun Earth Connection Coronal and Heliospheric Investigation) imaging suites of the two STEREO spacecraft. A catalogue of 79 polar jets is presented, identified from simultaneous EUV and white-light coronagraph observations, taken during the time period March 2007 to April 2008, when solar activity was at a minimum. The twin spacecraft angular separation increased during this time interval from 2 to 48 degrees. The appearances of the coronal jets were always correlated with underlying small-scale chromospheric bright points. A basic characterization of the morphology and identification of the presence of helical structure were established with respect to recently proposed models for their origin and temporal evolution. Though each jet appeared morphologically similar in the coronagraph field of view, in the sense of a narrow collimated outward flow of matter, at the source region in the low corona the jet showed different characteristics, which may correspond to different magnetic structures. A classification of the events with respect to previous jet studies shows that amongst the 79 events there were 37 Eiffel tower-type jet events, commonly interpreted as a small-scale (～35 arc?sec) magnetic bipole reconnecting with the ambient unipolar open coronal magnetic fields at its loop tops, and 12 lambda-type jet events commonly interpreted as reconnection with the ambient field happening at the bipole footpoints. Five events were termed micro-CME-type jet events because they resembled the classical coronal mass ejections (CMEs) but on much smaller scales. The remaining 25 cases could not be uniquely classified. Thirty-one of the total number of events exhibited a helical magnetic field structure, indicative for a torsional motion of the jet around its axis of propagation. A few jets are also found in equatorial coronal holes. In this study we present sample events for each of the jet types using both, STEREO A and STEREO B, perspectives. The typical lifetimes in the SECCHI/EUVI (Extreme UltraViolet Imager) field of view between 1.0 to 1.7 R _⊙ and in SECCHI/COR1 field of view between 1.4 to 4 R _⊙ are obtained, and the derived speeds are roughly estimated. In summary, the observations support the assumption of continuous small-scale reconnection as an intrinsic feature of the solar corona, with its role for the heating of the corona, particle acceleration, structuring and acceleration of the solar wind remaining to be explored in more detail in further studies.  相似文献   

西班牙的房地产泡沫:城市化与城市建设     

Onofre Rullan  SòniaVives-Miró  JesúsM.GonzálezPérez  尹子潇  顾朝林  陈明玉 《地理研究》2016,35(7):1383-1396

聚焦于西班牙1996-2007年间的房地产泡沫,此次危机与西班牙前两次经历的地产泡沫有着相似的背景条件：将住房建设作为利好投机性投资。但几次泡沫供给结构却不同：此次住房供给主要为分散式,不同于以往的集中供应;旅游地产大量出现;房屋拥有型社会形成。作者认为供给结构的改变并非危机的主要原因,并提出了造成房地产泡沫的四个关键要素：符合一定条件的土地、土地规划的配合、充足的资金与可获得的土地所有权。结论是：政策的制定直接影响土地利用、发展规划、金融系统与个人资产、造成住房由使用品变为投机投资的对象、银行体系信用缺乏保障,最终导致了住房库存量陡增,大量房屋拆除事件与失业率攀升等经济和社会方面的不良影响。  相似文献