Fragmentation Assessment using the FragScan System: Quality of a Blast     

J. Schleifer  B. Tessier 《Fragblast: International Journal for Blasting and Fragmentation》2002,6(3):321-331

Checking the quality of a blast may be considered as subjective. Checking this quality will require measuring objective parameters. One of them is the resulting fragmentation of the blasted product. Numerous fragmentation 'measuring' systems have been developed and marketed, based on image-processing. This presentation of FragScan will illustrate advantages and difficulties when using such a system. FragScan is essentially defending a policy of large and representative sampling. The purpose is to show how fragmentation is discriminating both productivity and profit of quarry operations on a blast-by blast basis. The next step will then be to 'drive' the blasting process to reach a 'better' fragmentation. Other applications require the fragmentation as an essential result: this is the case for large boulders used in structure-reinforcement. Several case-studies have shown that FragScan can be used for quality-control, checking size-distribution of the product according to the requirements of the end-user. Only clear thinking about the precise use of such a 'measurement' will further the success of this task.  相似文献   

Preservation potential of highstand coastal sedimentary bodies in a macrotidal basin: Example from the Bay of Mont-Saint-Michel, NW France     

Isabelle Billeaud  Bernadette Tessier  Bruno Caline 《Sedimentary Geology》2007,202(4):754-775

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Study of the spatial and historical distribution of sediment inorganic contamination in the Toulon bay (France)   总被引：4，自引：0，他引：4  

Tessier E  Garnier C  Mullot JU  Lenoble V  Arnaud M  Raynaud M  Mounier S 《Marine pollution bulletin》2011,62(10):2075-2086

This study presents trace elements levels in surface and deep sediments of the Toulon bay (SE France) subjected to anthropogenic inputs (navy base, harbors, etc.). The studied elements (As, Cd, Cr, Cu, Hg, Ni, Pb, Zn) are defined as priority contaminants in aquatic systems. Fifty-five points scattered on the entire bay were sampled, allowing the determination of contaminants distribution with a high resolution. Several approaches were used to assess the degree of contamination and the potential toxicity of the Toulon bay sediments: comparison to the French legislation, surface-weighted average metal concentrations, enrichment factors (EF), geoaccumulation indices (Igeo), trace element stock calculation and comparison to sediment quality guidelines. A principal component analysis was performed to reveal common behavior of the studied contaminants. Results demonstrated the very high contamination of the small bay, especially in Hg (EF up to 1500), Cu, Pb and Zn, with export to the large bay further governed by hydrodynamics.  相似文献   

Interfacing the DIGICO flux-gate spinner magnetometer to an APPLE IIe microcomputer     

Piotr Tucholka  Jerôme Tessier 《Geophysical Journal International》1987,89(2):705-712

Summary. A hardware configuration and program are described for interfacing a DIGICO spinner rock magnetometer to an APPLE microcomputer. This configuration provides full control of measurements and permits storage of the results on floppy or hard discs. A similar configuration can be used to operate the anisotropy unit.  相似文献   

Hydrodynamic behaviour of coarse bioclastic sand from shelly cheniers     

Pierre Weill  Dominique Mouazé  Bernadette Tessier  Jean‐Claude Brun‐Cottan 《地球表面变化过程与地形》2010,35(14):1642-1654

Cheniers from Mont‐Saint‐Michel bay (France) are coarse shelly sand ridges migrating on the mudflat up to the salt marshes where they accumulate and merge in a littoral barrier. In this macrotidal setting and low wave forcing, the cheniers are rarely submerged. However, they are found to move up to several metres during coincidence of spring tide and wave activity. Their processes of migration, morphology and internal structure (composition of the beddings, grain size, sorting and grain arrangement) are thought to be closely related to the hydrodynamic behaviour of the coarse and shelly sediment. This paper focuses on the hydrodynamic behaviour of bioclastic sand sampled from the cheniers: settling velocities of the shell fragments were measured using a 2 m long sedimentation tube. Thresholds of motion under unidirectional current, velocity and turbulence vertical profiles were characterized in a small recirculating flume using Laser Doppler Anemometry (LDA). The flat‐shaped bioclastic particles feature low settling velocities and reveal a good resistance to the re‐suspension effect of the flow when imbricated in a sediment bed. The shear stress in the bottom boundary layer has been measured in the viscous and log sub‐layers. Nikuradse roughness heights (k_s) for shell debris beds of different sizes have been quantified. It is found that k_s ≈ 2·56d₅₀. This value is close to the ones used for classic rounded sand grains despite their major differences of shape. The dual behaviour of the shell fragments (low settling velocity, good resistance to unidirectional flow) should be considered as a key to understanding how this coarse material is transported across the tidal flat, and finally accumulated as cheniers. Further flume experiments including wave activity and tidal fluctuations are necessary to better quantify these complex processes. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Eustatic and hydrodynamic controls on the architecture of a deep shelf sand bank (Celtic Sea)   总被引：3，自引：0，他引：3  

Jean-Yves Reynaud  Bernadette Tessier  Jean-Noël Proust  Robert Dalrymple  Tania Marsset  Marc De Batist  Jean-François Bourillet  & Gilles Lericolais 《Sedimentology》1999,46(4):703-721

The architecture of a tidal sand bank in the south-eastern Celtic Sea was examined using very high-resolution seismic surveys. The bank comprises four depositional units. The lowest unit 1 is characterized by gently dipping (1–8°) strata that strike parallel to the length of the bank. Unit 1 is erosionally overlain by unit 2, which forms the bulk of the bank. This unit consists of stacked sets of downcurrent-dipping (7–12°) master bedding formed by climbing, sinuous-crested tidal dunes that are up to 20 m high. These deposits are locally incised by an anastomosed channel network (unit 3) that may represent a buried swatchway system. The upper part of the bank comprises wave-related deposits that are mainly preserved on the bank flanks (unit 4). The outer bank surface is erosional. The bank is believed to have formed during the last post-glacial sea-level rise. The facies evolution from unit 1 to unit 3 indicates an upward increase in tidal energy, mainly characterized by the thickening of dune cross-bed sets in unit 2. The majority of bank growth is inferred to have occurred in water depths of the order of 60 m. This evolution was controlled by relative sea-level rise, which is likely to have caused an episode of tidal resonance with associated strong tidal currents that were responsible for the incision of the deep, cross-cutting channels of unit 3. The transition to wave-dominated sedimentation in unit 4 is related to the decay of resonance with continued sea-level rise.  相似文献   

Upper intertidal rhythmites in the Mont-Saint-Michel Bay (NW France): Perspectives for paleoreconstruction     

Bernadette Tessier   《Marine Geology》1993,110(3-4):355-367

The Mont-Saint-Michel Bay constitutes a good present-day example of sedimentation and facies in an upper intertidal domain. The tangue, a specific sediment of this area, displays an alternated structure of sandy and silty-muddy beds generated by the dynamics of tidal currents. This tidal bedding is frequently characterized by a vertical organization determined by the cyclic evolution of tidal energy during a neap/spring cycle. The organisation mainly consists in thickness variation of the successive sand/mud couplets which represent the deposit of each semi-diurnal tidal cycle. This record of tidal cyclicity can be observed in a wide range of bedding from planar bedding to climbing ripple bedding. The investigations performed allowed to clarify the conditions of deposition and of short-term preservation of these tidal rhythmites. Most well recorded neap/spring cycles develop within protected environments and necessarily require high suspended sediment concentrations. Characteristic features of these modern tidal rhythmites, such as the number of tidal event recorded per neap/spring cycle, are discussed in order to select criteria for the recognition of tidal dynamics in ancient sediments. The use of such criteria should constitute a way to discriminate subtidal to upper intertidal deposits and to propose paleogeographic reconstructions.  相似文献   

Mercury methylation,demethylation and reduction rates in coastal and marine surface waters of the Mediterranean Sea     

M. Monperrus  E. Tessier  D. Amouroux  A. Leynaert  P. Huonnic  O.F.X. Donard 《Marine Chemistry》2007

In situ experiments using isotopically labeled mercury species (¹⁹⁹Hg(II) and Me²⁰¹Hg) are used to investigate mercury transformation mechanisms, such as methylation, demethylation and reduction, in coastal and marine surface waters of the Mediterranean Sea. The aim of this work is to assess the relative contribution of photochemical versus biological processes to Hg transformation mechanisms. For this purpose, potential transformation rates measured under diurnal and dark incubation conditions are compared with major biogeochemical parameters (i.e. hydrological and biological data) in order to obtain the relative contribution of various biotic and abiotic mechanisms in both surface (high light) and bottom (low light) waters of the euphotic zone. The results demonstrate that coastal and marine euphotic zones are significant reactors for all Hg transformations investigated (i.e. methylation, demethylation, reduction). A major outcome demonstrates that Hg methylation is taking place in oxic surface seawater (0.3–6.3% day^− 1) and is mainly influenced by pelagic microorganism abundance and activities (phyto- and bacterioplankton). This evidences a new potential MeHg source in the marine water column, especially in oligotrophic deep-sea basins in which biogeochemistry is mostly governed by heterotrophic activity. For coastal and marine surface waters, although MeHg is mainly photochemically degraded (6.4–24.5% day^− 1), demethylation yields observed under dark condition may be attributed to microbial or chemical pathways (2.8–10.9% day^− 1). Photoreduction and photochemical reactions are the major mechanisms involved in DGM production for surface waters (3.2–16.9% day^− 1) but bacterial or phytoplanktonic reduction of Hg(II) cannot be excluded deeper in the euphotic zone (2.2–12.3% day^− 1). At the bottom of the euphotic zone, photochemical processes are thus avoided due to the attenuation of UV-visible sunlight radiation allowing biotic processes to be the most significant. These results suggest a new potential route for Hg species cycling in surface seawater and especially at the maximum biomass depth located at the bottom of the euphotic zone (i.e. maximum chlorophyll fluorescence). In this environment, DGM production and demethylation mechanisms are thus probably reduced whereas Hg methylation is enhanced by autotrophic and heterotrophic processes. Experimental results on mercury species uptake during these investigations further evidenced the strong affinity of MeHg for biogenic particles (i.e. microorganisms) that correspond to the first trophic level of the pelagic food web.  相似文献   

New techniques for integral field spectroscopy – II. Performance of the GNIRS IFU     

Jeremy Allington-Smith  Cornelis M. Dubbeldam  Robert Content  David Robertson  James Turner  Bernadette Rodgers  Jonathan Elias  Joris Gerssen †  Mark Swinbank 《Monthly notices of the Royal Astronomical Society》2007,376(2):785-792

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Dual-frequency ADCPs measuring turbidity     

Frédéric Jourdin  Caroline Tessier  Pierre Le Hir  Romaric Verney  Michel Lunven  Sophie Loyer  André Lusven  Jean-François Filipot  Jérémy Lepesqueur 《Geo-Marine Letters》2014,34(4):381-397

A pair of self-contained acoustic Doppler current profilers (SC-ADCPs) operating with different frequencies were moored on a muddy sea bottom at about 20 m depth in the Bay of Vilaine off the French Atlantic coast. With their acoustic beams oriented upwards, the SC-ADCPs ensonified most of the water column. The results of several months of in situ recorded echo intensity data spanning 2 years (2003 to 2004) from the dual-frequency ADCPs are presented in this paper. The aim was to estimate suspended particle mass concentration and mean size. A concentration index CI is proposed for the estimation of particle concentration. Based on theory the CI—unlike the volume backscatter strength—does not depend on particle size. Compared with in situ optical data, the CI shows reasonable precision but not increased with respect to that of the highest-frequency backscatter strength. Concerning the mean particle size, despite a lack of quantitative validation with optical particle-size measurements, the method yielded a qualitative discrimination of mineral (small) and organic (large) particles. This supports the potential of dual-frequency ADCPs to quantitatively determine particle size. A cross-calibration of the transducers of each ADCP shows that a specific component of the precision of the backscatter strength measured by ADCP depends on the acoustic frequency, the cell thickness and the ensemble integration time. Based on these results, the use of two ADCPs operating with distinctly different frequencies (two octaves apart) or a single dual-frequency ADCP is recommended.  相似文献