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121.
Chunhui Lu Adrian D. Werner Craig T. Simmons Neville I. Robinson Jian Luo 《Ground water》2013,51(2):219-228
In this study, we examine the maximum net extraction rate from the novel arrangement of an injection‐extraction well pair in a coastal aquifer, where fresh groundwater is reinjected through the injection well located between the interface toe and extraction well. Complex potential theory is employed to derive a new analytical solution for the maximum net extraction rate and corresponding stagnation‐point locations and recirculation ratio, assuming steady‐state, sharp‐interface conditions. The injection‐extraction well‐pair system outperforms a traditional single extraction well in terms of net extraction rate for a broad range of well placement and pumping rates, which is up to 50% higher for an aquifer with a thickness of 20 m, hydraulic conductivity of 10 m/d, and fresh water influx of 0.24 m2/d. Sensitivity analyses show that for a given fresh water discharge from an inland aquifer, a larger maximum net extraction is expected in cases with a smaller hydraulic conductivity or a smaller aquifer thickness, notwithstanding physical limits to drawdown at the pumping well that are not considered here. For an extraction well with a fixed location, the optimal net extraction rate linearly increases with the distance between the injection well and the sea, and the corresponding injection rate and recirculation ratio also increase. The analytical analysis in this study provides initial guidance for the design of well‐pair systems in coastal aquifers, and is therefore an extension beyond previous applications of analytical solutions of coastal pumping that apply only to extraction or injection wells. 相似文献
122.
Considering climatic uncertainties in management planning is a prerequisite for sustainable forest management (SFM). The aim
of the study was to evaluate climate change vulnerability of the current SFM strategy for commercial forests managed by the
Austrian Federal Forests. To that end vulnerability indicators were defined in a stakeholder process (selected indicators
were productivity, timber and carbon stocks, biodiversity, disturbances, a tree species’ position in fundamental niche space,
silvicultural flexibility and cost intensity) and their performance under climate change scenarios assessed with an ecosystem
model. Multi criteria analysis techniques were employed in a partial aggregation of indicators to locate forest stands on
a vulnerability surface. Results revealed high vulnerability particularly in the second half of the twenty-first century,
where 39.6% of the 164.550 ha study area were assessed highly vulnerable to climate change, indicating a strong decline in
the functions and services represented by the indicator system. Water-limited sites on calcareous bedrock were most negatively
affected whereas assessment units at higher altitudes responded predominately positive to climate warming. The presented approach,
transparently integrating multiple management objectives and allowing a quantitative comparison of vulnerabilities between
sites and management strategies, contributes to the development of operational and efficient climate change adaptation measures
in forest management. 相似文献
123.
Juliet G. Crider David Frank Stephen D. Malone Michael P. Poland Cynthia Werner Jacqueline Caplan-Auerbach 《Bulletin of Volcanology》2011,73(2):175-189
Mount Baker volcano displayed a short interval of seismically-quiescent thermal unrest in 1975, with high emissions of magmatic
gas that slowly waned during the following three decades. The area of snow-free ground in the active crater has not returned
to pre-unrest levels, and fumarole gas geochemistry shows a decreasing magmatic signature over that same interval. A relative
microgravity survey revealed a substantial gravity increase in the ~30 years since the unrest, while deformation measurements
suggest slight deflation of the edifice between 1981–83 and 2006–07. The volcano remains seismically quiet with regard to
impulsive volcano-tectonic events, but experiences shallow (<3 km) low-frequency events likely related to glacier activity,
as well as deep (>10 km) long-period earthquakes. Reviewing the observations from the 1975 unrest in combination with geophysical
and geochemical data collected in the decades that followed, we infer that elevated gas and thermal emissions at Mount Baker
in 1975 resulted from magmatic activity beneath the volcano: either the emplacement of magma at mid-crustal levels, or opening
of a conduit to a deep existing source of magmatic volatiles. Decadal-timescale, multi-parameter observations were essential
to this assessment of magmatic activity. 相似文献
124.
G��nther J. Redhammer Anatoliy Senyshyn Martin Meven Georg Roth Sebastian Prinz Astrid Pachler Gerold Tippelt Clemens Pietzonka Werner Treutmann Markus Hoelzel Bj?rn Pedersen Georg Amthauer 《Physics and Chemistry of Minerals》2011,38(2):139-157
The compound NaFeGe2O6 was grown synthetically as polycrystalline powder and as large single crystals suitable for X-ray and neutron-diffraction experiments to clarify the low temperature evolution of secondary structural parameters and to determine the low temperature magnetic spins structure. NaFeGe2O6 is isotypic to the clinopyroxene-type compound aegirine and adopts the typical HT-C2/c clinopyroxene structure down to 2.5?K. The Na-bearing M2 polyhedra were identified to show the largest volume expansion between 2.5?K and room temperature, while the GeO4 tetrahedra behave as stiff units. Magnetic susceptibility measurements show a broad maximum around 33?K, which marks the onset of low-dimensional magnetic ordering. Below 12?K NaFeGe2O6 transforms to an incommensurately modulated magnetic spin state, with k?=?[0.323, 1.0, 0.080] and a helical order of spins within the M1-chains of FeO6 octahedra. This is determined by neutron-diffraction experiments on a single crystal. Comparison of NaFeGe2O6 with NaFeSi2O6 is given and it is shown that the magnetic ordering in the latter compound, aegirine, also is complex and is best described by two different spin states, a commensurate one with C2??/c?? symmetry and an incommensurate one, best being described by a spin density wave, oriented within the (1 0 1) plane. 相似文献
125.
Francesco Di Benedetto Daniele Borrini Andrea Caneschi Gabriele Fornaciai Massimo Innocenti Alessandro Lavacchi Carlo Andrea Massa Giordano Montegrossi Werner Oberhauser Luca A. Pardi Maurizio Romanelli 《Physics and Chemistry of Minerals》2011,38(6):483-490
An extensive characterisation of the magnetic properties of synthetic powders of kuramite, with formal composition Cu3SnS4, was performed. Powders were investigated through superconducting quantum interference device (SQUID) magnetometry, electron paramagnetic resonance (EPR) spectroscopy, X-ray powder diffraction (XRPD), scanning and transmission electron microscopies (SEM and TEM) and microanalysis. SEM and TEM reveal the presence of nanodimensioned particles. XRPD clearly shows that Cu3SnS4 crystallised in a cubic sphalerite-type structural model, in spite of the stannite-type tetragonal structure described for the natural phase. This difference arises from a full random distribution of cations. Synthetic kuramite nanopowders exhibit a marked paramagnetism, originated by the presence of Cu(II), definitely assessed by EPR measurements. Moreover, the overall magnetic behaviour of the sample cannot be simply ascribed to diluted paramagnetism, and this suggests the presence of strong superexchange interactions among Cu(II) ions even at room temperature. The main consequences of these results are the definitive assessment of the chemical formula Cu(I)2Cu(II)SnS4 and of a random distribution of Cu(II), Cu(I) and Sn(IV) ions within the available tetrahedral sites. 相似文献
126.
Charles A. Stock Michael A. Alexander Nicholas A. Bond Keith M. Brander William W.L. Cheung Enrique N. Curchitser Thomas L. Delworth John P. Dunne Stephen M. Griffies Melissa A. Haltuch Jonathan A. Hare Anne B. Hollowed Patrick Lehodey Simon A. Levin Jason S. Link Kenneth A. Rose Ryan R. Rykaczewski Jorge L. Sarmiento Ronald J. Stouffer Franklin B. Schwing Francisco E. Werner 《Progress in Oceanography》2011,88(1-4):1-27
The study of climate impacts on Living Marine Resources (LMRs) has increased rapidly in recent years with the availability of climate model simulations contributed to the assessment reports of the Intergovernmental Panel on Climate Change (IPCC). Collaboration between climate and LMR scientists and shared understanding of critical challenges for such applications are essential for developing robust projections of climate impacts on LMRs. This paper assesses present approaches for generating projections of climate impacts on LMRs using IPCC-class climate models, recommends practices that should be followed for these applications, and identifies priority developments that could improve current projections. Understanding of the climate system and its representation within climate models has progressed to a point where many climate model outputs can now be used effectively to make LMR projections. However, uncertainty in climate model projections (particularly biases and inter-model spread at regional to local scales), coarse climate model resolution, and the uncertainty and potential complexity of the mechanisms underlying the response of LMRs to climate limit the robustness and precision of LMR projections. A variety of techniques including the analysis of multi-model ensembles, bias corrections, and statistical and dynamical downscaling can ameliorate some limitations, though the assumptions underlying these approaches and the sensitivity of results to their application must be assessed for each application. Developments in LMR science that could improve current projections of climate impacts on LMRs include improved understanding of the multi-scale mechanisms that link climate and LMRs and better representations of these mechanisms within more holistic LMR models. These developments require a strong baseline of field and laboratory observations including long time series and measurements over the broad range of spatial and temporal scales over which LMRs and climate interact. Priority developments for IPCC-class climate models include improved model accuracy (particularly at regional and local scales), inter-annual to decadal-scale predictions, and the continued development of earth system models capable of simulating the evolution of both the physical climate system and biosphere. Efforts to address these issues should occur in parallel and be informed by the continued application of existing climate and LMR models. 相似文献
127.
Kord Ernstson Werner Mayer Andreas Neumair Dirk Sudhaus 《Central European Journal of Geosciences》2011,3(4):385-397
Sudden collapse of the Quaternary soil to form sinkholes on the order of meters and tens of meters has been a geologic phenomenon within living memory in a localized area north of Lake Chiemsee in Southeast Germany. Failing a satisfying explanation, a relation with an undefined glaciation process has always been proposed. Excavations and geophysical measurements at three newly affected sites show underground features such as prominent sandy-gravelly intrusions and extrusions typical of rock liquefaction processes well known to occur during strong earthquakes. Since strong earthquakes can reasonably be excluded to have affected the area under discussion, it has been suggested that the observed widespread liquefaction is related with the recently proposed Holocene Chiemgau meteorite impact event. Except for one earlier proposed but unassertive relation between impact and liquefaction, the obviously direct association of both processes in the Chiemgau area emphasizes that observed paleoliquefaction features need not necessarily have originated solely from paleoseismicity but can provide a recognizable regional impact signature. 相似文献
128.
Michio J. Kishi Shin-ichi Ito Bernard A. Megrey Kenneth A. Rose Francisco E. Werner 《Journal of Oceanography》2011,67(1):3-16
The evolution of the North Pacific Ecosystem Model for Understanding Regional Oceanography (NEMURO) family of models to study
marine ecosystems is reviewed. Applications throughout the North Pacific have shown the models to be robust and to be able
to reproduce 1D, 2D and 3D components of nutrient, carbon cycle and biogeochemical cycles as well as aspects of the lower
trophic levels ecosystem (phyto- and zooplankton). NEMURO For Including Saury and Herring, an extension that includes higher
trophic levels, can be run uncoupled or coupled to NEMURO. In the uncoupled mode, the growth and weight of an individual fish
is computed using plankton densities simulated by NEMURO but with no feedback between fish consumption and plankton mortality.
In the coupled mode, the feeding, growth and weight of a representative fish are computed, and prey removals due to feeding
by fish appear as mortality terms on the prey. The NEMURO family of models continues to evolve, including effects of the microbial
loop and iron limitation at lower trophic levels, and full life cycle, multi-species and multi-generational simulations at
higher trophic levels. We outline perspectives for future end-to-end modeling efforts that can be used to study marine ecosystems
in response to global environmental change. 相似文献
129.
Gas phase transport according to chemical fluid transport (CFT) in Earth's crust as well as in the solar nebula is characterized by very high transport efficiency. Systematic investigations of mobilization, transport and deposition of gaseous MeX (Me = metal, X = F or Cl) compounds by solid gas equilibrium reactions are suitable to explain numerous extensive accumulations of minerals and ores. More than 40 of the considered chemical elements form volatile MeX compounds. Some elements tend to form MeF compounds, whereas others are more likely to form MeCl compounds. Silicon reacts with HF to form SiF4 and replaces other elements to form MeF compounds at low temperature ranges. Accumulations caused by SiF4 transport explain the formation of numerous quartz varieties and silicate minerals in Earth's crust. Iron most likely reacts with HCl to form FeCl2 as well as FeCl3 and explain the formation of iron or iron compounds. Thermodynamically directed transport from cool to hot areas in connection with cyclic processes increases the transport efficiency of MeX-species. Such species are SiF4, Al2F6, POF3, Cu3Cl3, SnCl4, BF3, GeF4, GeCl4, Ga2Cl6, ZrF4, NbF5 and TiF4. The transport gases SiF4 and POF3 often react with environmental compounds forming pneumatolytic and metasomatical mineral accumulations. CFT is the “motor” of pneumatolytic and metasomatical processes. 相似文献
130.
Numerous ordered defect structures are known that are related to the sodium chloride (or MgO) structure type, thus they are basically cubic closest packed (ccp) arrangements with vacancies. For example the NbO type is an MgO type in which one quarter each of the anions and the cations are missing compared to the ccp in such a way that both anions and cations are in square-planar coordination. In spinel, Al2MgO4, one half of the octahedrally coordinated cations are missing compared with the MgO type and only one eighth of the tetrahedrally coordinated sites within the ccp are occupied. What these cases have in common is that all these derivatives are rather dense. This is different in pharmacosiderite, K[Fe4(OH)4As3O12]. 6 to 7H2O, where one half of the anion positions, three quarters of the octahedral sites and five eighth of the tetrahedral sites remain vacant, compared to the spinel type. Pharmacosiderite is a wide open porous structure with zeolitic properties. We are illustrating these relationships using a Bärnighausen symmetry tree and by tables relating the various structure types to each other. 相似文献