Book reviews     

L. A. Endersbee  J. Kraus  H. Malina  A. Watznauer  G. Haas  L. Müller 《Rock Mechanics and Rock Engineering》1970,2(1):71-74

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A Comparison between WCS and OPeNDAP for Making Model Results and Data Products Available through the Internet     

Fedor Baart  Gerben de Boer  Wim de Haas  Gennadii Donchyts  Marc Philippart  Mark van Koningsveld  Maarten Plieger 《Transactions in GIS》2012,16(2):249-265

Numerical models produce output with a large number of variables, grid cells and time steps. The same applies to algorithms that produce gridded datasets from sparse or abundant raw data. Further use of the resulting data products has been challenging, especially for dissemination outside the institute of origin. Due to the gradually increasing size of data products, simply downloading copies of them is becoming impossible. A gradual transition from traditional download methods to web services is therefore observed. Web services allow for on‐the‐fly access to subsets of data that were hitherto considered as indivisible granules. Here we compare the most mature candidates to serve gridded data through the web: the Open‐source Project for a Network Data Access Protocol (OPeNDAP) and Web Coverage Service (WCS) protocols. In the framework of the new Dutch National Model and Data Centre (NMDC.eu) a distributed data storage has been created by coupling OPeNDAP servers. A WCS service layer is provided for the same data. This allows us to compare OPeNDAP and WCS. Using several use cases, we compare the usability, performance and features of the two protocols.  相似文献   

Influence of high-pressure processing on the structure and memory effect of synthetic layered double hydroxides     

Jaqueline C. Rodrigues  Tania Maria Haas Costa  Márcia R. Gallas  Celso C. Moro 《Physics and Chemistry of Minerals》2009,36(8):439-446

We investigate the structural evolution of synthetic layered double hydroxides (LDH) samples, processed at room temperature and high-pressure (up to 7.7 GPa) in a toroidal chamber with two pressure-transmitting media, lead and graphite, using X-ray diffraction, thermogravimetry and N₂-adsorption isotherms techniques. The X-ray patterns of compacted samples show a decrease in the peak intensities. For both pressure-transmitting media, our samples revealed a reduction of the basal d-spacing for the (003) plane when processed at 7.7 GPa. The expected high-pressure-induced amorphization was not observed. Surprisingly, we find high-pressure processing to have a strong influence on the memory effect of the LDH, due essentially to the reduction of the surface area and pore closing. Even when immersed in water, our samples did not recover the LDH structure, when either calcined at 450°C and compacted at 7.7 GPa, or calcined at 700°C and immediately compacted at 2.5 and 7.7 GPa.  相似文献   

Recent sediment transport and accumulation on the NW Iberian margin     

T. C. E. van Weering  H. C. de Stigter  W. Boer  H. de Haas 《Progress in Oceanography》2002,52(2-4)

Five transects across the NW Iberian margin were studied in the framework of the EU-funded Ocean Margin EXchange II (OMEX II) project, to determine and establish recent sediment and organic carbon transport and accumulation processes and fluxes.On the Galician shelf and shelf edge, resuspension of sediments resulting in well-developed bottom nepheloid layers was observed at all stations, but transport of suspended sediment appears largely confined to the shelf. On the continental slope, only very dilute bottom nepheloid layers were present, and intermediate nepheloid layers were only occasionally seen. This suggests that cross-slope transfer of particles is limited by the prevailing northerly directed shelf and slope currents.Optical backscatter and ADCP current measurements by the BOBO lander, deployed at 2152 m depth on the Galician slope, indicated that particles in the bottom boundary layer were kept in suspension by tidal currents with highest speeds between 15–25 cm s⁻¹. Net currents during the recording period August 6th–September 10th 1998, were initially directed along-slope toward the NNW, but later turned off-slope toward the SW.The separation of the water masses on the slope from the sediment-laden shelf water by the along-slope current regime is reflected in the recent sedimentary deposits of the Galician shelf and slope. Apart from compositional differences, shelf deposits differ from those on the slope by their higher flux of excess ²¹⁰Pb (0.57–5.37 dpm cm⁻²y⁻¹ versus 0.11–3.00 dpm cm⁻²y⁻¹), a much higher sediment accumulation rate (315.6–2295.9 g m⁻²y⁻¹ versus 10.9–124.7 g m⁻²y⁻¹) and organic carbon burial rate (1.01–34.30 g m⁻²y⁻¹ versus 0.01–0.69 g m⁻²y⁻¹).In contrast to the observations on the Galician margin, pronounced nepheloid layers occurred in the Nazaré Canyon, which extended to considerably greater water depths. This indicates that significantly greater transport of fine-grained particles in both the INL and the BNL was occurring within the canyon, as reflected in the exceptionally high ²¹⁰Pb excess flux (up to 34.09 dpm cm⁻²y⁻¹), mass accumulation rates (maximum 9623.1 g m⁻²y⁻¹) and carbon burial fluxes (up to 180.91 g m⁻²y⁻¹) in the sediment. However, radioisotope fluxes in the lower canyon were only slightly higher than at comparable depths on the Galician margin. This suggests that transport and rapid accumulation is focused on the upper and middle part of the canyon, from where it is episodically released to the deep sea. Compared to the Galician margin, the Nazaré Canyon may be considered as an important organic carbon depocenter on short time-scales, and a major conduit for particulate matter transport to the deep sea on >100 y time-scales.  相似文献   

Modelling of sediment supply from torrent catchments in the Western Alps using the sediment contributing area (SCA) approach     

Moritz Altmann  Florian Haas  Tobias Heckmann  Frédéric Liébault  Michael Becht 《地球表面变化过程与地形》2021,46(5):889-906

The production of coarse sediment in mountain landscapes depends mainly on the type and activity of geomorphic processes and topographic and natural conditions (e.g. vegetation cover) of these catchments. The supply of sediment from these slopes to mountain streams and its subsequent transport lead to sediment connectivity, which describes the integrated coupled state of these systems. Studies from the Northern Calcareous Alps show that the size of the sediment contributing area (SCA), a subset of the drainage area that effectively delivers sediment to the channel network, can be used as a predictor of sediment delivery to mountain streams. The SCA concept is delineated on a digital elevation model (DEM) using a set of rules related to the steepness and length of slopes directly adjacent to the channel network, the gradient of the latter and the vegetation cover. The present study investigates the applicability of this concept to the Western Alps to identify geomorphologically active areas and to estimate mean annual sediment yield (SY) in mainly debris-flow-prone catchments. We use a statistical approach that shows a parameter optimisation and a linear regression of SY on SCA extent. We use a dataset of ~25 years of assessed coarse sediment accumulation in 35 sediment retention basins. In the investigated catchments, sediment transport is governed by several factors, mainly by the extent of vegetation-free areas with a minimum slope of 23° that is coupled to the channel network with a very low gradient of the latter. With our improved framework, we can show that the SCA approach can be applied to catchments that are widely distributed, in a large spatial scale (hectare area) and very heterogeneous in their properties. In general, the investigated catchments show high connectivity, resulting in significant correlations between long-term average yield and the size of the SCA.  相似文献   

Spitzer observations of M33 and the hot star, H ii region connection     

Robert H. Rubin  Janet P. Simpson  Sean W. J. Colgan  Reginald J. Dufour  Gregory Brunner  Ian A. McNabb  Adalbert W. A. Pauldrach  Edwin F. Erickson  Michael R. Haas  Robert I. Citron 《Monthly notices of the Royal Astronomical Society》2008,387(1):45-62

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On‐Site Vapor‐Phase Analysis as a Novel Approach for Monitoring Groundwater Wells     

David T. Adamson  Thomas E. McHugh  Michal W. Rysz  Roberto Landazuri  Mir Ahmad Seyedabbasi  Patrick E. Haas  Charles J. Newell 《Ground Water Monitoring & Remediation》2014,34(2):42-59

The results of comprehensive field testing of on‐site vapor‐phase‐based groundwater monitoring methods are presented to demonstrate their utility as a robust and cost‐effective approach for rapidly obtaining volatile organic compounds (VOCs) concentration data from a monitoring well. These methods—which rely on sensitive, commercially available field equipment to analyze vapor in equilibrium with groundwater—proved easy to implement and can be tailored to site‐specific needs, including multilevel sampling. During field testing, low‐flow groundwater concentrations could be reasonably estimated using submerged passive vapor diffusion samplers or field equilibration of collected groundwater (R² = 0.85 to 0.96). These two methods are not as reliant on in‐well mixing to overcome vertical stratification within wells as simpler headspace methods. The importance of well and aquifer‐specific factors on concentration data (and therefore method selection) is highlighted, including the effect of changing in‐well patterns due to seasonal temperature gradients. Results indicated that vertical stratification was relatively limited within the set of wells included in these studies, resulting in similar performance for short depth‐discrete passive vapor diffusion samplers (constructed from 40‐mL vials) and longer samplers (2.5 to 5 feet in length) designed to cover a larger portion of the screened interval. A year‐long, multi‐event evaluation demonstrated that vapor‐phase‐based monitoring methods are no more variable than conventional groundwater monitoring methods, with both types subject to similar spatial and temporal variability that can be difficult to reduce. Vapor sampling methods represent a promising approach for estimation of groundwater concentrations by reducing the cost liabilities associated with monitoring while providing a more sustainable approach.  相似文献   

Supersonic jet formation and propagation in x-pinches     

D. M. Haas  S. C. Bott  J. Kim  D. A. Mariscal  R. E. Madden  Y. Eshaq  U. Ueda  G. Collins IV  K. Gunasekera  F. N. Beg  J. P. Chittenden  N. Niasse  C. A. Jennings 《Astrophysics and Space Science》2011,336(1):33-40

Observations of supersonic jet propagation in low-current x-pinches are reported. X-pinches comprising of four 7.5 ??m diameter tungsten wires were driven by an 80 kA, 50 ns current pulse from a compact pulser. Coronal plasma surrounding the wire cores was accelerated perpendicular to their surface due to the global J×B force, and traveled toward the axis of the x-pinch to form an axially propagating jet. These jets moved towards the electrodes and, late in time (??150 ns), were observed to propagate well above the anode with a velocity of 3.3±0.6×10⁴ m/s. Tungsten jets remained collimated at distances of up to 16 mm from the cross point, and an estimate of the local sound speed gives a Mach number of ??6. This is the first demonstration that supersonic plasma jets can be produced using x-pinches with such a small, low current pulser. Experimental data compares well to three-dimensional simulations using the GORGON resistive MHD code, and possible scaling to astrophysical jets is discussed.  相似文献   

Runout analysis of a large rockfall in the Dolomites/Italian Alps using LIDAR derived particle sizes and shapes     

Florian Haas  Tobias Heckmann  Volker Wichmann  Michael Becht 《地球表面变化过程与地形》2012,37(13):1444-1455

LiDAR data were used to quantify and analyse a rockfall event which occurred in 2003 in the Western Dolomites (Italian Alps). In addition to previously existing airborne laserscanning (ALS) data, high resolution terrestrial laserscanning (TLS) data were collected. By using the original point clouds, the volume, axial ratio and runout length of single boulders as well as the surface roughness in the runout zone of the rockfall were derived. The total volume of the rockfall event of approximately 10 000 m³ was estimated by a reconstruction of the pre‐event surface at the detachment zone. The analysis of the laser scanning data of the accumulation zone revealed a power law scaling for boulder volumes larger than 8 m³. The dependence of runout length on boulder volume is complex; it is moderated by particle sphericity. In addition, we used ALS and TLS data to derive the spatial distribution of surface roughness on the talus cone. TLS allow for more accurate roughness mapping than ALS data, but for most applications the point density of ALS data seems to be sufficiently high to derive measures of roughness. Different sampling approaches for plane fitting on the scale of 5 m did not show significant effects besides the computational time. The results of our analyses provide important perspectives for rockfall modelling and process understanding with potential applications in both ‘applied’ (natural hazards) and ‘pure’ geomorphological research. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

MTBE, TBA, and TAME Attenuation in Diverse Hyporheic Zones     

by James E. Landmeyer  Paul M. Bradley  Donald A. Trego  Kevin G. Hale  Joseph E. Haas II 《Ground water》2010,48(1):30-41

Groundwater contamination by fuel-related compounds such as the fuel oxygenates methyl tert -butyl ether (MTBE), tert -butyl alcohol (TBA), and tert -amyl methyl ether (TAME) presents a significant issue to managers and consumers of groundwater and surface water that receives groundwater discharge. Four sites were investigated on Long Island, New York, characterized by groundwater contaminated with gasoline and fuel oxygenates that ultimately discharge to fresh, brackish, or saline surface water. For each site, contaminated groundwater discharge zones were delineated using pore water geochemistry data from 15 feet (4.5 m) beneath the bottom of the surface water body in the hyporheic zone and seepage-meter tests were conducted to measure discharge rates. These data when combined indicate that MTBE, TBA, and TAME concentrations in groundwater discharge in a 5-foot (1.5-m) thick section of the hyporheic zone were attenuated between 34% and 95%, in contrast to immeasurable attenuation in the shallow aquifer during contaminant transport between 0.1 and 1.5 miles (0.1 to 2.4 km). The attenuation observed in the hyporheic zone occurred primarily by physical processes such as mixing of groundwater and surface water. Biodegradation also occurred as confirmed in laboratory microcosms by the mineralization of U- ¹⁴C-MTBE and U-¹⁴C-TBA to ¹⁴CO₂ and the novel biodegradation of U- ¹⁴C-TAME to ¹⁴CO₂ under oxic and anoxic conditions. The implication of fuel oxygenate attenuation observed in diverse hyporheic zones suggests an assessment of the hyporheic zone attenuation potential (HZAP) merits inclusion as part of site assessment strategies associated with monitored or engineered attenuation.  相似文献