Mesozoic (Late Jurassic) palynomorphs and charcoal from a sandstone pebble from Quaternary glacial deposits of the North Sea

The palynological contents as well as macroscopic charcoal fragments from a calcareous sandstone pebble from Quaternary glacial deposits of the North Sea (80 km SW of the Dogger Bank) are described. The taxonomic composition of the palynoflora points to a Late Jurassic (or Late Jurassic/Early Cretaceous) age of the sandstone. The charcoal is interpreted as direct evidence of palaeo‐wildfire occurring during this period in the source area of the sediments of this particular sandstone. This finding, together with already published data on Mesozoic deposits, allows to conclude that wildfires were obviously widespread during this period in the area of the modern day North Sea and adjacent areas. Copyright © 2012 John Wiley & Sons, Ltd.     

Building frequency fluctuations from continuous monitoring of ambient vibrations and their relationship to temperature variations

Building frequencies (fundamental and higher modes) are a critical parameter especially in the field of structural health monitoring mainly based on the stability of the structural dynamic parameters of individual building (frequencies, damping and modes shape). One of the most used methods to find out these parameters is based on the use on ambient vibration analysis. In this work, we study the fluctuations over a month period of the fundamental frequencies (transverse and longitudinal) of a 3.5-story RC-building made of 2 identical units connected by a structural joint. Time independent building frequencies is a strong assumption; as illustrated by our experiment showing that over an observation period of a month, building frequencies fluctuate of about 3.5 %. A clear correlation is found between the building frequency fluctuations and temperature variations, with a phase-shift interpreted as the characteristic time of heat diffusion within the walls. This allows: (1) determining the thermal diffusivity of the structure, (2) inferring its relative stiffness variations, and (3) showing that its Young modulus varies linearly with temperature.     

Regularized Bayesian estimation for GEV-B-splines model

Large observed datasets are not stationary and/or depend on covariates, especially, in the case of extreme hydrometeorological variables. This causes the difficulty in estimation, using classical hydrological frequency analysis. A number of non-stationary models have been developed using linear or quadratic polynomial functions or B-splines functions to estimate the relationship between parameters and covariates. In this article, we propose regularised generalized extreme value model with B-splines (GEV-B-splines models) in a Bayesian framework to estimate quantiles. Regularisation is based on penalty and aims to favour parsimonious model especially in the case of large dimension space. Penalties are introduced in a Bayesian framework and the corresponding priors are detailed. Five penalties are considered and the corresponding priors are developed for comparison purpose as: Least absolute shrinkage and selection (Lasso and Ridge) and smoothing clipped absolute deviations (SCAD) methods (SCAD1, SCAD2 and SCAD3). Markov chain Monte Carlo (MCMC) algorithms have been developed for each model to estimate quantiles and their posterior distributions. Those approaches are tested and illustrated using simulated data with different sample sizes. A first simulation was made on polynomial B-splines functions in order to choose the most efficient model in terms of relative mean biais (RMB) and the relative mean-error (RME) criteria. A second simulation was performed with the SCAD1 penalty for sinusoidal dependence to illustrate the flexibility of the proposed approach. Results show clearly that the regularized approaches leads to a significant reduction of the bias and the mean square error, especially for small sample sizes (n < 100). A case study has been considered to model annual peak flows at Fort-Kent catchment with the total annual precipitations as covariates. The conditional quantile curves were given for the regularized and the maximum likelihood methods.     

Performance of Foundations in Sabkha Soil: Numerical Investigation

Sabkha or salt flat soil is one of the most unpredictable and potentially dangerous soils in the Middle East. This soil covers a large and strategically important area of the Arabian Gulf coast, as it contains the world biggest oil reserve and a number of petrochemical plants are either have been built or are scheduled to be built in this area. The performance of shallow and deep foundations in the Eastern Province of Saudi Arabia’s sabkha soil is investigated numerically using the finite element method. The parameters used to simulate this soil in the numerical models were based on a large number of laboratory tests to determine the shear strength and stiffness parameters of the sabkha soil. In addition, the characteristics of the interface between the foundation and soil used in the numerical model were established from shear box tests that were conducted to evaluate the concrete-sabkha soil interface properties. The developed numerical model was calibrated/verified using the results of full-scale pile load testing program from an ongoing project to further enhance the accuracy of the results. A parametric study was then conducted using the verified model to establish the performance characteristics of foundations constructed in sabkha soil and provide guidelines for their design.     

Plant assemblage from Opole,southern Poland: New data on Late Cretaceous vegetation of the northern part of the European Province

This paper presents the results of studies on plant macroremains found in the upper Turonian of the Folwark Quarry, Opole, Poland, associated with palynological studies of the host rocks. In addition to a few macrofossils (gymnosperm wood, conifer Geinitzia reichenbachii and fern ?Didymosorus) rich sporomorphs (bryophyte, lycopod and fern spores, conifer and angiosperm pollen grains) and marine palynomorphs (mainly dinoflagellate cysts) were recorded. The palynological analysis revealed that the vegetation on the neighbouring land (the East Sudetic Island) in the late Turonian was much more diverse than could be reconstructed based on only macrofossil remains. The latter are taxonomically restricted and dominated by one gymnosperm species (Geinitzia reichenbachii), which make them similar to most neighbouring, coeval Central European assemblages. Its over representation is, thus, a result of taphonomy.     

Comparison between VES and 2D imaging techniques for delineating subsurface plume of hydrocarbon contaminated water southeast of Karbala City,Iraq

Shallow vertical electrical sounding (VES) technique with Schlumberger electrode array (maximum distance between current electrodes was 50 m) through 25 VES points distributed on five traverses. Two 2D imaging lines with Wenner electrode array 30 m each corresponding to two VES traverses were conducted near well water contaminated with hydrocarbon materials at Karbala Governorate, Iraq. It is found that these techniques can give good results in delineating contaminated and clear zones but the 2D imaging technique was better in delineating the boundaries of the contaminated water plume and gave clear image of the subsurface distribution of the contaminated water vertically and horizontally.