Feeding preferences of herring (Clupea harengus) and sprat (Sprattus sprattus) in the southern Baltic Sea     

Casini  Michele; Cardinale  Massimiliano; Arrhenius  Fredrik 《ICES Journal of Marine Science》2004,61(8):1267-1277

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Statistical tests for regional seismic phase characterizations   总被引：1，自引：0，他引：1  

L. Persson 《Journal of Seismology》2003,7(1):19-33

In seismic analysis some assumptions are often made aboutthe data, e.g. stationarity and Gaussianity. This is not obvious for all realseismic data. Here, we use statistical tests for characterization of regionalseismic data. We apply tests for stationarity, symmetry, linearity, andtime-reversibility. In the analysis we use twelve regional seismic events inFennoscandia recorded with the seismic small-aperture arrays NORESS,ARCESS and FINESA at hypocentral distances in the range from 160 to1580 km. For the tests we use the regional phases Pn, secondary P, Sn and Lg-phases and the preceding noise. Two of the eventsare explosions, two are rockbursts and eight are earthquakes. Theperformance and possibilities of using statistical tests based on bispectra, asa complementary tool for conventional analysis of seismic phases isdemonstrated. The preceding noise recorded before the first onset of theP-wave for the twelve events is tested to be spatially stationarybetween each channel within each array and temporal stationary in 21consecutive time windows of 3.2 sec each. Also, the preceding noise issymmetric and linear. The seismic phases defined by the symmetry test asnon-Gaussian (not symmetric) are all linear. This means a linear model canbe used to characterize both the noise and the phases. The first P-phase for the two explosions is characterized as non-Gaussian at thethree arrays. For all 36 possibly first P-phase arrivals at the three arraystations, 23 are non-Gaussian. The second P-phase is non-Gaussian at13 of 36 data records, the S-phase at eleven of 36 and the Lg-phase at nine of 36. For all the four phases more than 32 of possible36 are time-reversible.  相似文献   

Stochastic Structural Modeling   总被引：3，自引：0，他引：3  

Lars Holden  Petter Mostad  Bjørn Fredrik Nielsen  Jon Gjerde  Chris Townsend  Signe Ottesen 《Mathematical Geology》2003,35(8):899-914

A consistent stochastic model for faults and horizons is described. The faults are represented as a parametric invertible deformation operator. The faults may truncate each other. The horizons are modeled as correlated Gaussian fields and are represented in a grid. Petrophysical variables may be modeled in a reservoir before faulting in order to describe the juxtaposition effect of the faulting. It is possible to condition the realization on petrophysics, horizons, and fault plane observations in wells in addition to seismic data. The transmissibility in the fault plane may also be included in the model. Four different methods to integrate the fault and horizon models in a common model is described. The method is illustrated on an example from a real petroleum field with 18 interpreted faults that are handled stochastically.  相似文献   

Differential nocturnal cooling in the landscape detected by mobile measurements     

P. Persson 《Theoretical and Applied Climatology》1997,56(3-4):215-224

Summary In June 1986 mobile air temperature measurements were performed in the Kivik area in Sweden. The measuring trips were repeated each hour during a night with calm and clear weather conditions. Along a loop, 8650 m long and traversing a hilly landscape, the air temperature was measured at four levels (0.2, 1.0, 2.0 and 3.0 m a g). In this study the results are focused on the measurements at the standard level, 2.0 m a g, in order to make it easier to compare this study with earlier mobile studies.Sudden rises in air temperature at 2.0 m occurred at a number of elevated locations along the loop, at a max. rate of 3.5°C/hour, indicative of the influence of dynamic turbulence. Lower parts of the loop did show a drop in air temperature at the same time, with a max. of 3.8°C/hour, indicative of cold air influence. In most earlier studies the mobile measurements were compensated for the nocturnal cooling in order to make it possible to directly compare the different measurement points. This study highlights the problems due to turbulence as mentioned above. It also stresses the fact that more reference measurements at more than one point along a loop are needed in hilly terrain.With 7 Figures  相似文献   

Nephelinite lavas at early stage of rift initiation (Hanang volcano,North Tanzanian Divergence)     

Céline Baudouin  Fleurice Parat  Carole M. M. Denis  Fredrik Mangasini 《Contributions to Mineralogy and Petrology》2016,171(7):64

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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   

Industrial minerals and rocks, aggregates and natural stones in the Nordic countries     

Kurt Johansson Rune B. Larsen Markku J. Lehtinen Lars Persson Mika Raeisaenen Stig A. Schack Pedersen Paer Weihed Nils-Gunnar Wik 《《幕》》2008,31(1):133-139

The Nordic countries, including Greenland, have a long tradition in mining. The industrial minerals sector is expanding in most Nordic countries and extensive development has taken place during the last few years. The main commodities mined are carbonate rocks, quartz, feldspar, apatite, olivine and talc.
A number of diferent types of dimension stones are quarried in all countries. Rock aggregates are increasingly important, replacing sand and gravel aggregate as construction materials in some countries due to the need to protect ground water supplies.  相似文献   

A multi-proxy reconstruction of spatial and temporal variations in Asian summer temperatures over the last millennium   总被引：1，自引：0，他引：1  

Feng?Shi  Quansheng?GeEmail author  Bao?Yang  Jianping?Li  Fengmei?Yang  Fredrik?Charpentier?Ljungqvist  Olga?Solomina  Takeshi?Nakatsuka  Ninglian?Wang  Sen?Zhao  Chenxi?Xu  Keyan?Fang  Masaki?Sano  Guoqiang?Chu  Zexin?Fan  Narayan?P.?Gaire  Muhammad?Usama?Zafar 《Climatic change》2015,131(4):663-676

To investigate climate variability in Asia during the last millennium, the spatial and temporal evolution of summer (June–July–August; JJA) temperature in eastern and south-central Asia is reconstructed using multi-proxy records and the regularized expectation maximization (RegEM) algorithm with truncated total least squares (TTLS), under a point-by-point regression (PPR) framework. The temperature index reconstructions show that the late 20th century was the warmest period in Asia over the past millennium. The temperature field reconstructions illustrate that temperatures in central, eastern, and southern China during the 11th and 13th centuries, and in western Asia during the 12th century, were significantly higher than those in other regions, and comparable to levels in the 20th century. Except for the most recent warming, all identified warm events showed distinct regional expressions and none were uniform over the entire reconstruction area. The main finding of the study is that spatial temperature patterns have, on centennial time-scales, varied greatly over the last millennium. Moreover, seven climate model simulations, from the Coupled Model Intercomparison Project Phase 5 (CMIP5), over the same region of Asia, are all consistent with the temperature index reconstruction at the 99 % confidence level. Only spatial temperature patterns extracted as the first empirical orthogonal function (EOF) from the GISS-E2-R and MPI-ESM-P model simulations are significant and consistent with the temperature field reconstruction over the past millennium in Asia at the 90 % confidence level. This indicates that both the reconstruction and the simulations depict the temporal climate variability well over the past millennium. However, the spatial simulation or reconstruction capability of climate variability over the past millennium could be still limited. For reconstruction, some grid points do not pass validation tests and reveal the need for more proxies with high temporal resolution, accurate dating, and sensitive temperature signals, especially in central Asia and before AD 1400.  相似文献   

The importance of reduced meat and dairy consumption for meeting stringent climate change targets     

Fredrik Hedenus  Stefan Wirsenius  Daniel J. A. Johansson 《Climatic change》2014,124(1-2):79-91

For agriculture, there are three major options for mitigating greenhouse gas (GHG) emissions: 1) productivity improvements, particularly in the livestock sector; 2) dedicated technical mitigation measures; and 3) human dietary changes. The aim of the paper is to estimate long-term agricultural GHG emissions, under different mitigation scenarios, and to relate them to the emissions space compatible with the 2 °C temperature target. Our estimates include emissions up to 2070 from agricultural soils, manure management, enteric fermentation and paddy rice fields, and are based on IPCC Tier 2 methodology. We find that baseline agricultural CO₂-equivalent emissions (using Global Warming Potentials with a 100 year time horizon) will be approximately 13 Gton CO₂eq/year in 2070, compared to 7.1 Gton CO₂eq/year 2000. However, if faster growth in livestock productivity is combined with dedicated technical mitigation measures, emissions may be kept to 7.7 Gton CO₂eq/year in 2070. If structural changes in human diets are included, emissions may be reduced further, to 3–5 Gton CO₂eq/year in 2070. The total annual emissions for meeting the 2 °C target with a chance above 50 % is in the order of 13 Gton CO₂eq/year or less in 2070, for all sectors combined. We conclude that reduced ruminant meat and dairy consumption will be indispensable for reaching the 2 °C target with a high probability, unless unprecedented advances in technology take place.  相似文献   

Transmissivity of solar radiation through crowns of single urban trees—application for outdoor thermal comfort modelling     

Janina Konarska  Fredrik Lindberg  Annika Larsson  Sofia Thorsson  Björn Holmer 《Theoretical and Applied Climatology》2014,117(3-4):363-376

Trees play an important role in mitigating heat stress on hot summer days, mainly due to their ability to provide shade. However, an important issue is also the reduction of solar radiation caused by trees in winter, in particular at high latitudes. In this study, we examine the transmissivity of total and direct solar radiation through crowns of single street trees in Göteborg, Sweden. One coniferous and four deciduous trees of species common in northern European cities were selected for case study. Radiation measurements were conducted on nine clear days in 2011–2012 in foliated and leafless tree conditions using two sunshine pyranometers—one located in shade of a tree and the other one on the roof of an adjacent building. The measurements showed a significant reduction of total and direct shortwave radiation in the shade of the studied trees, both foliated and leafless. Average transmissivity of direct solar radiation through the foliated and defoliated tree crowns ranged from 1.3 to 5.3 % and from 40.2 to 51.9 %, respectively. The results confirm the potential of a single urban tree to reduce heat stress in urban environment. However, the relatively low transmissivity through defoliated trees should be considered while planning street trees in high latitude cities, where the solar access in winter is limited. The results were used for parameterisation of SOLWEIG model for a better estimation of the mean radiant temperature (T_mrt). Measured values of transmissivity of solar radiation through both foliated and leafless trees were found to improve the model performance.  相似文献