Thermally induced cation redistribution in Fe-bearing oxy-dravite and potential geothermometric implications     

Ferdinando Bosi  Henrik Skogby  Ulf Hålenius 《Contributions to Mineralogy and Petrology》2016,171(5):47

  相似文献   

Provenance of Holocene beach sand in the Western Iberian margin: the use of the Kolmogorov–Smirnov test for the deciphering of sediment recycling in a modern coastal system          下载免费PDF全文

Manuel Francisco Pereira  Luís Albardeiro  Cristina Gama  Martim Chichorro  Mandy Hofmann  Ulf Linnemann 《Sedimentology》2016,63(5):1149-1167

Detrital zircons from Holocene beach sand and igneous zircons from the Cretaceous syenite forming Cape Sines (Western Iberian margin) were dated using laser ablation – inductively coupled plasma – mass spectrometry. The U–Pb ages obtained were used for comparison with previous radiometric data from Carboniferous greywacke, Pliocene–Pleistocene sand and Cretaceous syenite forming the sea cliff at Cape Sines and the contiguous coast. New U–Pb dating of igneous morphologically simple and complex zircons from the syenite of the Sines pluton suggests that the history of zircon crystallization was more extensive (ca 87 to 74 Ma), in contrast to the findings of previous geochronology studies (ca 76 to 74 Ma). The U–Pb ages obtained in Holocene sand revealed a wide interval, ranging from the Cretaceous to the Archean, with predominance of Cretaceous (37%), Palaeozoic (35%) and Neoproterozoic (19%) detrital‐zircon ages. The paucity of round to sub‐rounded grains seems to indicate a short transportation history for most of the Cretaceous zircons (ca 95 to 73 Ma) which are more abundant in the beach sand that was sampled south of Cape Sines. Comparative analysis using the Kolmogorov–Smirnov statistical method, analysing sub‐populations separately, suggests that the zircon populations of the Carboniferous and Cretaceous rocks forming the sea cliff were reproduced faithfully in Quaternary sand, indicating sediment recycling. The similarity of the pre‐Cretaceous ages (>ca 280 Ma) of detrital zircons found in Holocene sand, as compared with Carboniferous greywacke and Pliocene–Pleistocene sand, provides support for the hypothesis that detritus was reworked into the beach from older sedimentary rocks exposed along the sea cliff. The largest percentage of Cretaceous zircons (<ca 95 Ma) found in Holocene sand, as compared with Pliocene–Pleistocene sand (secondary recycled source), suggests that the Sines pluton was the one of the primary sources that became progressively more exposed to erosion during Quaternary uplift. This work highlights the application of the Kolmogorov–Smirnov method in comparison of zircon age populations used to identify provenance and sediment recycling in modern and ancient detrital sedimentary sequences.  相似文献   

An Experimental Approach to the Development of Dynamic Pressure to Improve Grout Spread     

A. N. Ghafar  A. Mentesidis  A. Draganovic  S. Larsson 《Rock Mechanics and Rock Engineering》2016,49(9):3709-3721

  相似文献   

Stress Wave Interaction Between Two Adjacent Blast Holes     

Changping Yi  Daniel Johansson  Ulf Nyberg  Ali Beyglou 《Rock Mechanics and Rock Engineering》2016,49(5):1803-1812

  相似文献   

Uncertainties in Grout Penetrability Measurements; Evaluation and Comparison of Filter pump,Penetrability Meter and Short Slot     

A. Nejad Ghafar  S. Ali Akbar  M. Al-Naddaf  A. Draganovic  S. Larsson 《Geotechnical and Geological Engineering》2018,36(2):747-762

To measure grout penetrability in fractured hard rock, various measuring instruments have been developed over the years. Penetrability meter and Filter pump have been designed to use in both the lab and the field. Short slot has been applicable mainly in the lab due to its complexity. The fact, that these instruments have been built based on different assumptions, limitations, and test conditions, makes their results occasionally in contradict. Deficiency in design of the instruments as well as the methods of evaluating grout penetrability is additionally a basis for uncertainty in results. This study is an experimental effort to determine and thoroughly perceive the nature of the most governing uncertainties in grout penetrability measurements. The test apparatus, procedure, and method used to evaluate the grout penetrability in both Penetrability meter and Filter pump were thus modified. The aim was to control the corresponding uncertainties and make their limitations and test conditions as similar as possible with the ones in Short slot. The results suggested that to obtain a more realistic evaluation of the grout penetrability, measurement should be accomplished at both the high and the low pressures with sufficient grout volume using Short slot. Moreover, application of both Filter pump and Penetrability meter is no longer recommended due to the revealed uncertainties.  相似文献   

International and national climate policies for aviation: a review     

Jörgen Larsson  Anna Elofsson  Thomas Sterner  Jonas Åkerman 《Climate Policy》2019,19(6):787-799

Aviation constitutes about 2.5% of all energy-related CO₂ emissions and in addition there are non-CO₂ effects. In 2016, the ICAO decided to implement a Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) and in 2017 the EU decided on faster emission reductions in its Emissions Trading System (EU ETS), which since 2012 includes the aviation sector. The effects of these policies on the expected development of air travel emissions from 2017 to 2030 have been analyzed. For the sample country Sweden, the analysis shows that when emissions reductions in other sectors are attributed to the aviation sector as a result of the EU ETS and CORSIA, carbon emissions are expected to reduce by ?0.8% per year (however if non-CO₂ emissions are included in the analysis, then emissions will increase). This is much less than what is needed to achieve the 2°C target. Our analysis of potential national aviation policy instruments shows that there are legally feasible options that could mitigate emissions in addition to the EU ETS and CORSIA. Distance-based air passenger taxes are common among EU Member States and through increased ticket prices these taxes can reduce demand for air travel and thus reduce emissions. Tax on jet fuel is an option for domestic aviation and for international aviation if bilateral agreements are concluded. A quota obligation for biofuels is a third option.

Key policy insights

• Existing international climate policies for aviation will not deliver any major emission reductions.

• Policymakers who want to significantly push the aviation sector to contribute to meeting the 2°C target need to work towards putting in place tougher international policy instruments in the long term, and simultaneously implement temporary national policy instruments in the near-term.

• Distance-based air passenger taxes, carbon taxes on jet fuel and quota obligations for biofuels are available national policy options; if they are gradually increased, and harmonized with other countries, they can help to significantly reduce emissions.

  相似文献   

Computational homogenization of uncoupled consolidation in micro‐heterogeneous porous media     

Fredrik Larsson  Kenneth Runesson  Fang Su 《国际地质力学数值与分析法杂志》2010,34(14):1431-1458

Variationally consistent homogenization is exploited for the analysis of transient uncoupled consolidation in micro‐heterogeneous porous solids, whereby the classical approach of first‐order homogenization for stationary problems is extended to transient problems. Homogenization is then carried out in the spatial domain on representative volume elements (RVE), which are introduced in quadrature points in standard fashion. Along with the classical averages, a higher‐order conservation quantity is obtained. An iterative FE²‐algorithm is devised for the case of nonlinear permeability and storage coefficients, and it is applied to pore pressure changes in asphalt‐concrete (particle composite). Various parametric studies are carried out, in particular, with respect to the influence of the ‘substructure length scale’ that is represented by the size of the RVE's. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Turbulent exchange above a pine forest II. Organized structures   总被引：1，自引：0，他引：1  

Hans Bergström  Ulf Högström 《Boundary-Layer Meteorology》1989,49(3):231-263

Data from two 100-min runs on the turbulent atmospheric wind, temperature and humidity fields above a pine forest have been analysed using conditional sampling techniques. With the aid of the temperature time series, ramp events were identified and all fields were averaged in order to remove smaller scale turbulence and random low-frequency turbulence, and to map the organized structures revealed in this way. It is shown that the turbulent fluxes of momentum, heat and humidity, determined from these ramp-events, in fact constitute a large part of the total fluxes, about 90% during the actual events.On average, the duration of and the time between ramps were found to be about 35 s and 100 s, respectively. These periods were also found in the uw-, wT- and wq-cospectra, not only in the data analysed in this paper, but in the major part of all day-time data from this forest site (about 80 runs of 60 or 100 min). This indicates that the ramp events described arc a rather common phenomenon. The organized structures also have remarkable resemblance to near-wall structures observed in the laboratory.  相似文献   

Compactional behavior of fine-grained sediments — examples from Deep Sea Drilling Project cores     

Ulf Bayer  Andreas Wetzel 《International Journal of Earth Sciences》1989,78(3):807-819

Laboratory experiments, statistical analysis of field data and theoretical models are combined in the attempt to derive standard compaction curves for various deep-sea sediments which are in compaction equilibrium with the overburden. A revised and generalized version of Athy's law together with laboratory experiments allows the classification of sediments in terms of the amount of porewater structurally bound to the particles' surfaces. Especially suction pressure experiments are useful in quantifying the forces that bind water on the particle surfaces. The sediments analyzed almost range from systems of »suspended grains« to nearly perfect »colloidal systems«. The methods and equations required to derive the relevant parameters are given for both, downhole porosity/density measurements and laboratory experiments.

---

Zusammenfassung Die Synthese experimenteller Labordaten, statistischer Analysen von Messungen an Kernen und theoretischer Modellierung der Kompaktion im Gleichgewicht mit der Auflast ermöglicht die Definition von Typ-Kurven für das Kompaktionsverhalten von verschiedenen Tiefsee-Sedimenten. Eine erweiterte und verbesserte Form der Athy'schen Gleichung erlaubt zusammen mit Laborexperimenten, Sedimente entsprechend des Anteils an strukturell gebundenem Porenwasser zu klassifizieren. Anhand von Saugspannungsexperimenten können die Bindungskräfte zwischen Wasser und Partikeloberflächen abgeschätzt werden. Die untersuchten Sedimente reichen von »suspendierten Körnern« bis zu einem »kolloidalen System«. Die notwendigen Methoden und Gleichungen zur Bestimmung der relevanten Parameter aus Bohrlochdaten und Laborexperimenten werden diskutiert.

---

Résumé A partir d'une synthèse de résultats d'expériences de laboratoires, d'analyses statistiques de données de terrain et d'une modélisation théorique, il est possible d'établir des courbes standard du processus de compaction pour divers types de sédiments de mer profonde, pour lesquels la compaction est en équilibre avec la charge. Une version revue et généralisée de la loi d'Athy permet, en accord avec les résultats expérimentaux, de classer les sédiments selon la quantité d'eau intersticielle liée structuralement à la surface des particules. Les sédiments analysés correspondent à des systèmes qui vont du type à «grains suspendus» à des colloïdes presque parfaits. Les auteurs présentent une discussion détaillée des méthodes et des équations néssaires à l'obtention des paramètres significatifs tant à partir des expériences de laboratoire qu'à partir des mesures de porosité/densité effectuées dans les forages.

---

, , . Athy , , . . . .

  相似文献   

Turbulent characteristics of a shallow convective internal boundary layer     

Ann-Sofi Smedman  Ulf Högström 《Boundary-Layer Meteorology》1983,25(3):271-287

Turbulent characteristics of a 50 to 100 m deep convective internal boundary layer (I.B.L.) have been studied. The data were gathered at a flat coastal site (Näsudden on the island of Gotland, Sweden) during three consecutive days in May 1980 which were characterized by a steady, very stable stratified marine approach flow. The site is situated on a flat area ca. 1500 m from the shoreline. Only daytime runs have been analysed in the present paper. The sensible heat flux at the ground was typically 200 W m^-2 and was found to decrease more or less linearly with height throughout the I.B.L., being slightly negative at greater heights. The momentum flux was also found to decrease with height, but nevertheless shear production of turbulent kinetic energy was found to be large throughout the entire I.B.L. The analysis shows that the turbulent regime has a mixed character. Certain characteristics, such as the rate of growth of the I.B.L., appear to be almost entirely controlled by mechanical turbulence, while others, notably temperature variance and the spectrum of vertical velocity, scale remarkably well with w _* and z _i, in accordance with the results found in fully convective conditions during the experiments at Minnesota and Aschurch. Other turbulent characteristics, such as spectra of the horizontal wind components measured near the top of the I.B.L. tend to adhere to mixed-layer scaling in the high frequency range, exhibiting much increased energy in the lower (reduced) frequency range. Spectra of the velocity components from 10 m are shown to be in general agreement with findings from ‘ideal’, homogeneous sites (Kansas) when properly normalized, although the low frequency part of u- and v-spectra are slightly reduced compared to the case with deep convection.  相似文献