In memory of Charles David Keeling     

Pieter  Tans Bert  Bolin 《Tellus. Series B, Chemical and physical meteorology》2006,58(5):329-330

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Modelling the morphodynamic impact of offshore sandpit geometries     

Pieter C. Roos  Suzanne J.M.H. Hulscher  Huib J. de Vriend 《Coastal Engineering》2008

We investigate the hydrodynamic effects and morphodynamic impact of large-scale offshore sand extraction, for a variety of pit designs. We use a process-based idealized model for flow, sediment transport and bed evolution in a tide-dominated environment. Legislation and other practical considerations motivate our assumption that sandpits are both wide (horizontal dimensions of the order of kilometres) and shallow (the ratio of pit depth to water depth being small). This results in a semi-analytical tool that, unlike previous studies, enables a quick and extensive study into the effects of varying the physical characteristics as well as the pit design parameters. These parameters include pit length, width, and orientation with respect to the tide.  相似文献   

Isotope Dilution Determinations of Lu,Hf, Zr,Ta and W,and Hf Isotope Compositions of NIST SRM 610 and 612 Glass Wafers   总被引：1，自引：0，他引：1  

Oliver Nebel  Melanie L.A. Morel  Pieter Z. Vroon 《Geostandards and Geoanalytical Research》2009,33(4):487-499

Isotope dilution determinations of Lu, Hf, Zr, Ta and W are reported for nine test portions (five for W) of NIST SRM 610 and 612 glass wafers. Additionally, all test portions were analysed for their Hf isotope compositions. In general, high field strength elemental (HFSE) distributions in NIST SRM 610 and 612 were reproducible to ～± 1%, except for Zr (± 5%) in NIST SRM 612, and absolute reported concentrations agreed with previously published values, but with higher precision. The slightly worse reproducibility of Zr in NIST SRM 612 compared to other HFSE is interpreted to result from analytical scatter, rather than sample inhomogeneity. The analyses demonstrated elemental homogeneity for both glass wafers for samples of 1–2 mg with respect to the precision of the method, i.e., ± 1% or better. Average Hf isotope compositions for both glass wafers agreed within uncertainty and the weighted average of all determinations yielded a mean ¹⁷⁶Hf/¹⁷⁷Hf ratio of 0.282111 ± 0.000009 (95% confidence level). However, although mean values for NIST SRM 610 and 612 agreed within analytical limits, NIST SRM 610 test portions showed a tendency of systematically elevated isotope composition of ～ 0.5 _?Hf units when compared to NIST SRM 612, which may indicate a slightly more radiogenic Hf isotope composition of NIST SRM 610. The results of this study suggest that NIST SRM 610 and 612 are valuable calibrators for HFSE in situ analyses within the given uncertainties.  相似文献   

Stochastic methods for safety assessment of the flood defense system in the Scheldt Estuary of the Netherlands     

Mohammadreza Rajabalinejad  Tewfik Mahdi  Pieter van Gelder 《Natural Hazards》2010,55(1):123-144

In this study, we address the effective method to apply a novel reliability method integrated with finite element models to the safety assessment of pilot site Scheldt in the Netherlands. This site was considered as one of the three main pilot sites in Europe to assess the application of newly suggested techniques in order to reduce and manage the flood risk in the Floodsite project. , 2004–2009). The novel method of dynamic bounds (DB) is applied to this site after a successful experience in (Rajabalinejad in Reliability methods for finite element models, 1 edn. IOS Press, Amsterdam, 2009). In this study, the bi-functional response of the finite element model is considered, and the dimensional uncertainty is defined presenting the expected uncertainty for a certain dimension in the DB method. The uncertainty is used as a judgment tool to choose the dimension for the DB method for the desired accuracy. The results obtained by applying this technique are presented in this paper.  相似文献   

Benefits and hurdles of using brackish groundwater as a drinking water source in the Netherlands     

Pieter J. Stuyfzand  Klaasjan J. Raat 《Hydrogeology Journal》2010,18(1):117-130

The production of fresh drinking water from brackish groundwater by reverse osmosis (BWRO) is becoming more attractive, even in temperate climates. For successful application of BWRO, the following approach is advocated: (1) select brackish source groundwater with a large volume and a composition that will yield a concentrate (waste water) with low mineral saturation; (2) maintain the feed water salinity at a constant level by pumping several wells with different salinities; (3) keep the permeate-to-concentrate ratio low, to avoid supersaturation in the concentrate; (4) keep the system anoxic (to avoid oxidation reactions) and pressurized (to prevent formation of gas bubbles); and (5) select a confined aquifer for deep well injection where groundwater quality is inferior to the membrane concentrate. This approach is being tested at two BWRO pilot plants in the Netherlands. Research issues are the pumping of a stable brackish source water, the reverse osmosis system performance, membrane fouling, quality changes in the target aquifer as a result of concentrate disposal, and clogging of the injection well. First evaluations of the membrane concentrate indicate that it is crucial to understand the kinetics of mineral precipitation on the membranes, in the injection wells, and in the target aquifer.  相似文献   

Effect of interface characteristics on the influence coefficients of an embedded circular footing under horizontal and moment loading     

Djillali Amar Bouzid  Pieter A. Vermeer 《Geotechnical and Geological Engineering》2007,25(5):487-497

By means of a semi-analytical FE approach an embedded circular footing under monotonic horizontal and moment loading is studied. In a non-homogeneous soil whose shear modulus is characterized by a power law variation with depth, horizontal, rocking and coupled modes of displacement, expressed in terms of influence factors are thoroughly examined. The exponent α that controls the shape of the stiffness variation with depth is termed shear modulus factor. Surface influence coefficients are considered for the situations where the interface between the soil and the footing is either perfectly rough or perfectly smooth. First, results of semi-analytical FE analysis in the case of rough footing are established and compared with those of another numerical method. Results of comparison show good agreement. Then, for different values of α the surface influence coefficients are presented for an embedded footing in perfect smooth contact with soil. The metacentre is referred to as the depth at which there is no coupling between the sliding and the rocking modes of footing deformations. Expressions for location and horizontal influence coefficient corresponding to this particular depth are developed and their variations with α examined. The paper finishes by showing the effect of interface conditions on the soil normal stresses developed beneath the embedded circular footing for the case of loading applied at the footing top.  相似文献   

On 50th Anniversary of the Global Carbon Dioxide Record     

Georgii A Alexandrov  Martin Heimann  Chris D Jones  Pieter Tans 《Carbon balance and management》2007,2(1):11-2

The 50-year global CO₂ record led the way in establishing a scientific fact: modern civilization is changing important properties of the global atmosphere, oceans and biosphere. The evidence on which this scientific fact is based will be refined further, but the next challenge for scientists is broader. In addition to its traditional role in providing discovery, diagnosis, and prediction of the changes that are taking place on our planet, science has now also a role in helping society mitigate emissions by objectively quantifying them, and in helping adaptation by providing environmental forecasts on regional scales. Science is also expected to provide new options for society to tackle the transition to a new energy system, and to provide thorough environmental evaluation of all such options. This is what the meeting recognized as planetary responsibilities for scientists in the next 50 years.  相似文献   

Reply to Comment by Agrawal and Verma on “Tectonic classification of basalts with classification trees”     

Pieter Vermeesch 《Geochimica et cosmochimica acta》2007,71(13):3391-3392

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Diagnosing drought using the downstreamness concept: the effect of reservoir networks on drought evolution     

Pieter R. van Oel  Eduardo S. P. R. Martins  Alexandre C. Costa  Niko Wanders  Henny A. J. van Lanen 《水文科学杂志》2020,65(Z1):979-990

ABSTRACT

To effectively manage hydrological drought, there is an urgent need to better understand and evaluate its human drivers. Using the “downstreamness” concept, we assess the role of a reservoir network in the emergence and evolution of droughts in a river basin in Brazil. In our case study, the downstreamness concept shows the effect of a network of reservoirs on the spatial distribution of stored surface water volumes over time. We demonstrate that, as a consequence of meteorological drought and recovery, the distribution of stored volumes became spatially skewed towards upstream locations, which affected the duration and magnitude of hydrological drought both upstream (where drought was alleviated) and downstream (where drought was aggravated). The downstreamness concept thus appears to be a useful entry point for spatiotemporally explicit assessments of hydrological drought and for determining the likelihood of progression from meteorological drought to a human-modified hydrological drought in a basin.  相似文献   

Formation of offshore tidal sand banks triggered by a gasmined bed subsidence     

Pieter C. Roos  Suzanne J. M. H. Hulscher 《Continental Shelf Research》2002,22(18-19)

Offshore gasmining is an example of a human intervention with a morphological impact. On land, it is usually attended with a dish-like bed depression. We show that, if located at sea, such a bed depression can become morphodynamically active by triggering mechanisms related to tidal sand bank formation. To that end, a simple morphological model is considered which describes an erodible bed subject to a tidal wave in a shallow sea. The continuous subsidence is modelled by a sink term in the sediment balance. Then, a linear approximation is carried out to describe the bed evolution after the onset of subsidence. The results, presented in physical space, show that the subsidence triggers the formation of a sand bank pattern that gradually spreads around the centre of subsidence, at a rate that may go up to 160 m year⁻¹, depending on the tidal transport rate and the tidal eccentricity. The dimension of the depression does not affect the spreading rate nor the orientation of the sand banks, but it does influence their spacing. The main conclusion is that the horizontal extent of the area influenced by the bed depression by far exceeds that of the direct subsidence, thus showing that bed depressions on land and at sea indeed behave in fundamentally different ways. The results suggest that nonlinear effects are worthwhile to be investigated in order to describe finite amplitude development of sand banks as well as the interaction between subsidence and bed forms.  相似文献