Coalification stages from confined pyrolysis of an immature humic coal     

P. Landais  L. Gerard 《International Journal of Coal Geology》1996,30(4):285-301

An immature humic coal (subbituminous rank) from the Mahakam delta (Kutei basin, Kalimantan, Indonesia) was isothermally pyrolyzed in confined conditions at temperatures ranging from 250 to 400°C (10°C steps) at 700 bar pressure for 72 h. Solid, liquid and thermodesorbable phases originating from the pyrolyzates have been analyzed by different analytical techniques. Results indicate that a 10°C pyrolysis step is necessary to determine the timing and the sequence of the different transformations affecting the kerogen as well as the effluents. Four maturation/coalification stages are distinguished. Stage 1 (75–80 wt.% C) occurs when modifications mainly concern the oxygen-bearing functions of the kerogen. Stage 2 (82–85 wt.%o C) is characterized by the decrease of the aliphaticity and the primary cracking of the coal. Stage 3 (86–89 wt.% C) corresponds to the production of methane and the condensation of aromatic rings in the solid residue.  相似文献   

Ecosystem responses in the Rhine-Meuse delta during two decades after enclosure and steps toward estuary restoration     

Henk Smit  Gerard van der Velde  Rob Smits  Hugo Coops 《Estuaries and Coasts》1997,20(3):504-520

Changes in hydrology, and developments in morphology, water quality, and ecology of the Rhine-Meuse estuary after its enclosure in 1970 are analyzed on the basis of existing monitoring data. Annual averages of ammonium, nitrate plus nitrite, total phosphate, total lead, and chlorophyll-a concentrations as well as transparency of the water are presented. Abundances of some water bird species are given for the period 1970–1993, and the relative fish biomass for the period 1971–1988 is discussed. The gradual evolution led toward the dominance of bream. The area has developed toward a system with generally low natural ecological values. Ecological impacts of present sluice management are discussed and include the accumulation of contaminated sediments, disappearance of intertidal areas and nursery grounds for fish, disturbance of fish migration, and less mixing of river and seawater. Recent policy developments have brought the present management of the Haringvliet sluices back in to discussion. A recent policy document has presented several management alternatives, including partial and complete reopening of the sluices to permit saltwater intrusion. Three management options are compared in terms of costs and ecological benefits. It is concluded that a complete reopening, and thus a partial restoration of the estuarine characteristics, is most beneficial for the ecosystems of the area itselt, for the upstream Rhine and Meuse rivers, and for the adjacent North Sea, but costs amount to about 600 million US $.  相似文献   

The Global Stratotype Section and Point （GSSP） for the base of the Holocene Series/Epoch （Quaternary System/Period） in the NGRIP ice core   总被引：4，自引：0，他引：4  

Mike Walker  ;Sigfus Johnsen  ;Sune Olander Rasmussen  ;Jorgen-Peder Steffensen  ;Trevor Popp  ;Philip Gibbard  ;Wim Hoek  ;John Lowe  ;John Andrews  ;Svante Bjorck  ;Les Cwynar  ;Konrad Hughen  ;Peter Kershaw  ;Bernd Kromer  ;Thomas Litt  ;David J. Lowe  ;Takeshi Nakagawa  ;Rewi Newnham  ;Jakob Schwander 《《幕》》2008,31(2):264-267

The Greenland ice core from NorthGRIP （NGRIP） contains a proxy climate record across the Pleistocene-Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision.  相似文献   

Increasing the Power Production of Vertical-Axis Wind-Turbine Farms Using Synergistic Clustering     

Seyed Hossein Hezaveh  Elie Bou-Zeid  John Dabiri  Matthias Kinzel  Gerard Cortina  Luigi Martinelli 《Boundary-Layer Meteorology》2018,169(2):275-296

Vertical-axis wind turbines (VAWTs) are being reconsidered as a complementary technology to the more widely used horizontal-axis wind turbines (HAWTs) due to their unique suitability for offshore deployments. In addition, field experiments have confirmed that vertical-axis wind turbines can interact synergistically to enhance the total power production when placed in close proximity. Here, we use an actuator line model in a large-eddy simulation to test novel VAWT farm configurations that exploit these synergistic interactions. We first design clusters with three turbines each that preserve the omni-directionality of vertical-axis wind turbines, and optimize the distance between the clustered turbines. We then configure farms based on clusters, rather than individual turbines. The simulations confirm that vertical-axis wind turbines have a positive influence on each other when packed in well-designed clusters: such configurations increase the power generation of a single turbine by about 10 percent. In addition, the cluster designs allow for closer turbine spacing resulting in about three times the number of turbines for a given land area compared to conventional configurations. Therefore, both the turbine and wind-farm efficiencies are improved, leading to a significant increase in the density of power production per unit land area.  相似文献   

Upscaling of Hooke''s Law for Imperfectly Layered Rocks     

Gerard Rijpsma  Wouter Zijl 《Mathematical Geology》1998,30(8):943-969

In this paper, we consider the upscaling of Hooke's law and its parameters on the fine scale, to a similar law with upscaled parameters on a larger scale. It is assumed that the fine scale material properties of the rock are imperfectly layered. In the governing equations, the deviations from perfect layering introduce a small parameter that can be used in perturbation series expansions for the stress, the strain, and the displacement. In the approximation of order zero the upscaled compliance matrix contains the well-known Backus parameters; this approximation holds exactly for a perfect layering. However, many natural rock types are imperfectly layered and in that case the approximation of order zero may not be sufficiently accurate. Therefore, we consider also the first order corrections. The derivation and results are presented both for the most general case and for the much simpler case in which the fine scale Poisson ratio may be assumed constant. From thermodynamic principles, it follows that the compliance tensor is symmetric on the fine scale. However, it is shown that the argument for symmetry cannot be extended to upscaled rigidities. One of the most important conclusions is that upscaled compliance tensors are nonsymmetric when there are trends in the deviations from perfect layering.  相似文献   

On the Dependence of the Equilibrium Range of Sea Wave Spectra with Wave Age     

Gerard Caudal 《Boundary-Layer Meteorology》1998,86(1):29-45

Donelan and Pierson have proposed a semiphysical model of the equilibrium sea wave spectrum, based upon a parameterization of wave growth and dissipation terms. Their model is applicable for fully developed seas only. In the framework of Donelan and Pierson's approach, this paper explores the dependence of the equilibrium spectrum upon wave age. To this end, we examine how the dissipation through wave breaking is expected to vary with wave age, according to the approach proposed by Longuet-Higgins in 1969. The constraint imposed by Longuet-Higgins' theory requires an increase of the equilibrium spectrum F(k,0) in the wind direction with increasing inverse wave age U/C_p. This is in accordance with Banner's empirically deduced statement that F(k,0) is proportional to (U/C_p)^0.5 in the equilibrium range. Our inferred F(k,0) tends to increase more or less linearly with U/C_p (we find F(k,0) proportional to 1 + 0.25(U/C_p - 0.83), rather than through a power law. If a power law is fitted we obtain F(k,0) approximately proportional to (U/C_p)^0.35 for the range 0.83 < U/C_p > 5. Finally, the roughness length of the air-sea interface is inferred from our modelled spectrum through integration of the form drag over wave number under rough conditions. This shows a wave age dependence that is compatible with measurements of wind stress performed in the field at various wave ages.  相似文献   

2-D seismic trenching of colluvial wedges and faults     

David Sheley  Travis Crosby  Min Zhou  Jamie Giacoma  Jianhua Yu  Ruiqing He  Gerard T. Schuster   《Tectonophysics》2003,368(1-4):51

Images of the depth and shape of colluvial wedges by 3-D travel time tomography can be valuable in estimating the past history of ancient earthquakes and assessing the earthquake hazard of a fault. Unfortunately, 3-D seismic surveys can be both costly and time consuming. In this paper, we report our first successful results of detecting the shapes and depths of colluvial wedges with 2-D travel time tomography. The locations of the colluvial wedges are along the Oquirrh fault and the Salt Lake City segment of the Wasatch fault. We also report that the tomogram from one of our 2-D surveys suggests the possibility of detecting multiple colluvial wedges at depth. Using both reflection and tomographic images at another site clearly reveals the presence of a known shallow fault and the contact between native soil and recent fill. Our results suggest the synergistic use of both seismic tomography and reflection imaging, we denote as seismic trenching, as a means of detecting shallow colluvial wedges and faults. Seismic trenching has the potential to significantly expand the lateral extent and depth of investigation of paleoseismology.  相似文献   

A diatomaceous origin for long-chain diols and mid-chain hydroxy methyl alkanoates widely occurring in quaternary marine sediments: indicators for high-nutrient conditions     

Jaap S. Sinninghe Damsté  Sebastiaan Rampen  C. Rijpstra  Gerard Muyzer  Stefan Schouten 《Geochimica et cosmochimica acta》2003,67(7):1339-1348

For the first time a biological source for the long-chain alkyl 1,14-diols and 12-hydroxy methyl alkanoates, lipids widely occurring in the marine water column and sediments, has been identified. Cultures of Proboscia indica and Proboscia alata, rhizosolenoid diatoms belonging to the widespread diatom genus Proboscia, contain C₂₈, C_28:1, C₃₀, and C_30:1 alkyl 1,14-diols, and C₂₇ and C₂₉ 12-hydroxy methyl alkanoates as major neutral lipids. These components form a substantial fraction of lipid fractions from sediment traps or sediments, especially in areas with an elevated primary production such as upwelling regions. Examination of literature data reveals that as much as 20 to 35% of the total lipid flux in the Arabian Sea is derived from Proboscia diatoms during the start of the upwelling season. Their rapid transfer to the water-sediment interface may explain why corresponding 1,14-keto-ols, inferred oxidation products of diols, are hardly formed. These interpretations are supported by compound-specific carbon isotopic analysis of long-chain keto-ols and diols in surface sediments of the Arabian Sea. The data indicate that long-chain alkyl 1,14-diols and 12-hydroxy methyl alkanoates can be applied as indicators for high-nutrient conditions in the photic zone.  相似文献   

The motions of a ship in swallow water     

Gerard van Oortmerssen 《Ocean Engineering》1976,3(4)

A general formulation is given of the hydrodynamic forces on a ship, oscillating about a state of rest in 6df in response to excitation by a harmonic wave in shallow water. A method is described to obtain a numerical approximation of the velocity potential, describing the flow around the moving ship by means of a distribution of discrete three-dimensional sources.With this method it is possible to take the influence of a quay into account.Calculated values of wave excited forces, hydrodynamic coefficients and motions of a 200,000 tdw tanker in shallow water are presented and compared with experimental results.  相似文献   

Evolution of the western Barents Sea   总被引：2，自引：0，他引：2  

Jan Inge Faleide  Steinar T. Gudlaugsson  Gerard Jacquart 《Marine and Petroleum Geology》1984,1(2):123-150

Information from multichannel seismic reflection data complemented by seismic refraction, gravity and magnetics forms the basis for a regional structural and evolutionary model of the western Barents Sea during post-Caledonian times. The western Barents Sea contains a thick succession, locally > 10 km, of Upper Paleozoic to Cenozoic sedimentary rocks covering a basement of probably Caledonian origin. The area is divided into three regional geological provinces: (1) an east-west trending basinal province between 74°N and the coast of Norway; (2) an elevated platform area to the north towards Svalbard; and (3) the western continental margin. Several structural elements of different origin and age have been mapped within each of these provinces. The main stratigraphic sequence boundaries have been tentatively dated from available well information, correlation with the geology of adjacent areas, and correlation with the interregional unconformities caused by relative changes of sea level. The main structural elements were developed during three major post-Caledonian tectonic phases: the Svalbardian phase in Late Devonian to Early Carboniferous times, the Mid and Late Kimmerian phase in Mid Jurassic to Early Cretaceous times and Cenozoic tectonism related to the progressive northward opening of the Norwegian-Greenland Sea. The sediments are predicted to be of mainly clastic origin except for a thick sequence of Middle Carboniferous — Lower Permian carbonates and evaporites. Salt diapirs have developed in several sub-basins, especially in the Nordkapp Basin where they form continuous salt walls that have pierced through > 7 km of sediments.  相似文献