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  • 1
    Electronic Resource
    Electronic Resource
    Photoresponsive Behavior of Azobenzene-Based (Meth)acrylic (Co)polymers in Thin Films (1994)
    s.l. : American Chemical Society
    Macromolecules 27 (1994), S. 6201-6206 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00099a040
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  • 2
    Electronic Resource
    Electronic Resource
    Thermal Isomerization of Azobenzene-Based Acrylic Monomers and (Co)Polymers with Dimethylamino Substituents in Solution, Influence of Addition of (Poly)Acid, Copolymer Composition, Spacer Length, and Solvent Type (1995)
    s.l. : American Chemical Society
    Macromolecules 28 (1995), S. 2867-2873 
    Details
    ISSN: 1520-5835
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ma00112a036
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  • 3
    Electronic Resource
    Electronic Resource
    Improving a Regional Model Using Reduced Complexity and Parameter Estimation (2002)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 40 (2002), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The availability of powerful desktop computers and graphical user interfaces for ground water flow models makes possible the construction of ever more complex models. A proposed copper-zinc sulfide mine in northern Wisconsin offers a unique case in which the same hydrologic system has been modeled using a variety of techniques covering a wide range of sophistication and complexity. Early in the permitting process, simple numerical models were used to evaluate the necessary amount of water to be pumped from the mine, reductions in streamflow, and the drawdowns in the regional aquifer. More complex models have subsequently been used in an attempt to refine the predictions. Even after so much modeling effort, questions regarding the accuracy and reliability of the predictions remain.We have performed a new analysis of the proposed mine using the two-dimensional analytic element code GFLOW coupled with the nonlinear parameter estimation code UCODE. The new model is parsimonious, containing fewer than 10 parameters, and covers a region several times larger in areal extent than any of the previous models. The model demonstrates the suitability of analytic element codes for use with parameter estimation codes. The simplified model results are similar to the more complex models; predicted mine inflows and UCODE-derived 95% confidence intervals are consistent with the previous predictions. More important, the large areal extent of the model allowed us to examine hydrological features not included in the previous models, resulting in new insights about the effects that far-field boundary conditions can have on near-field model calibration and parameterization. In this case, the addition of surface water runoff into a lake in the headwaters of a stream while holding recharge constant moved a regional ground watershed divide and resulted in some of the added water being captured by the adjoining basin. Finally, a simple analytical solution was used to clarify the GFLOW model's prediction that, for a model that is properly calibrated for heads, regional drawdowns are relatively unaffected by the choice of aquifer properties, but that mine inflows are strongly affected. Paradoxically, by reducing model complexity, we have increased the understanding gained from the modeling effort.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.2002.tb02498.x
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  • 4
    Electronic Resource
    Electronic Resource
    Selecting MODFLOW Cell Sizes for Accurate Flow Fields (2001)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 39 (2001), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Contaminant transport models often use a velocity field derived from a MODFLOW flow field. Consequently, the accuracy of MODFLOW in representing a ground water flow field determines in part the accuracy of the transport predictions, particularly when advective transport is dominant. We compared MODFLOW ground water flow rates and MODPATH particle traces (advective transport) for a variety of conceptual models and different grid spacings to exact or approximate analytic solutions. All of our numerical experiments concerned flow in a single confined or semiconfined aquifer. While MODFLOW appeared robust in terms of both local and global water balance, we found that ground water flow rates, particle traces, and associated ground water travel times are accurate only when sufficiently small cells are used. For instance, a minimum of four or five cells are required to accurately model total ground water inflow in tributaries or other narrow surface water bodies that end inside the model domain. Also, about 50 cells are needed to represent zones of differing transmissivities or an incorrect flow field and (locally) inaccurate ground water travel times may result. Finally, to adequately represent leakage through aquitards or through the bottom of surface water bodies it was found that the maximum allowable cell dimensions should not exceed a characteristic leakage length λ, which is defined as the square root of the aquifer transmissivity times the resistance of the aquitard or stream bottom. In some cases a cell size of one-tenth of λis necessary to obtain accurate results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.2001.tb02481.x
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  • 5
    Electronic Resource
    Electronic Resource
    GROUND WATER HYDRAULICS CONSIDERATIONS REGARDING LANDFILLS (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 27 (1991), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Landfill siting and design guidelines or regulations differ from state to state. Most include hydrogeological criteria, referring to hydraulic conductivities, aquifers, ground water flow patterns, contaminant travel times, and distance between landfill and sensitive targets for contaminants, etc. However, almost all of the existing hydrogeological guidelines are incomplete, inconsistent, or both. The aquitard between landfill and regional aquifer frequently offers less resistance to leachate migration than compliance with regulations may suggest. Residence times of leachate, that makes it through the landfill liner, is often overestimated. Monitoring wells in the regional aquifer are unreliable detectors of local leaks in a landfill. If a landfill does leak, costly aquifer restoration is called for. For traditional landfill designs, ground water monitoring considerations suggest the siting over homogeneous sand and gravel aquifers, rather than over complex till environments. An alternative landfill design criterion is suggested, which is based on a negative hydraulic gradient underneath the landfill. This design guarantees ground water protection, simplifies landfill monitoring, and generally enhances the landfill economy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1991.tb01477.x
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  • 6
    Electronic Resource
    Electronic Resource
    Are Water Tables a Subdued Replica of the Topography? (2005)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Ground water 43 (2005), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The water table in unconfined aquifers is often believed to be a subdued replica of the topography or land surface. However, this assumption has not been widely tested and in some cases has been found to be in error. An analysis of ground water rise in regional unconfined aquifers, using both a two-dimensional boundary element model and a one-dimensional Dupuit-Forchheimer model, reveals the conditions under which the water table does or does not closely follow the topography. A simple decision criterion is presented to estimate in advance under which conditions the water table is expected to be largely unrelated to the topography and under which conditions the topography controls the position of the water table.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.2005.00090.x
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  • 7
    Electronic Resource
    Electronic Resource
    On using simple time-of-travel capture zone delineation methods (2005)
    Oxford, UK; Malden, USA : Blackwell Science Inc
    Ground water 43 (2005), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: As part of its Wellhead Protection Program, the U.S. EPA mandates the delineation of “time-of-travel capture zones” as the basis for the definition of wellhead protection zones surrounding drinking water production wells. Depending on circumstances the capture zones may be determined using methods that range from simply drawing a circle around the well to sophisticated ground water flow and transport modeling. The simpler methods are attractive when faced with the delineation of hundreds or thousands of capture zones for small public drinking water supply wells. On the other hand, a circular capture zone may not be adequate in the presence of an ambient ground water flow regime. A dimensionless time-of-travel parameter T˜ is used to determine when calculated fixed-radius capture zones can be used for drinking water production wells. The parameter incorporates aquifer properties, the magnitude of the ambient ground water flow field, and the travel time criterion for the time-of-travel capture zone. In the absence of interfering flow features, three different simple capture zones can be used depending on the value of T˜. A modified calculated fixed-radius capture zone proves protective when T˜ 〈 0.1, while a more elongated capture zone must be used when T˜ 〉1. For values of T˜ between 0.1 and 1, a circular capture zone can be used that is eccentric with respect to the well. Finally, calculating T˜ allows for a quick assessment of the validity of circular capture zones without redoing the delineation with a computer model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.2005.0035.x
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  • 8
    Electronic Resource
    Electronic Resource
    Simulating Ground Water-Lake Interactions: Approaches and Insights (2003)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 41 (2003), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Approaches for modeling lake-ground water interactions have evolved significantly from early simulations that used fixed lake stages specified as constant head to sophisticated LAK packages for MODFLOW. Although model input can be complex, the LAK package capabilities and output are superior to methods that rely on a fixed lake stage and compare well to other simple methods where lake stage can be calculated. Regardless of the approach, guidelines presented here for model grid size, location of three-dimensional flow, and extent of vertical capture can facilitate the construction of appropriately detailed models that simulate important lake-ground water interactions without adding unnecessary complexity. In addition to MODFLOW approaches, lake simulation has been formulated in terms of analytic elements. The analytic element lake package had acceptable agreement with a published LAK1 problem, even though there were differences in the total lake conductance and number of layers used in the two models. The grid size used in the original LAK1 problem, however, violated a grid size guideline presented in this paper. Grid sensitivity analyses demonstrated that an appreciable discrepancy in the distribution of stream and lake flux was related to the large grid size used in the original LAK1 problem. This artifact is expected regardless of MODFLOW LAK package used. When the grid size was reduced, a finite-difference formulation approached the analytic element results. These insights and guidelines can help ensure that the proper lake simulation tool is being selected and applied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.2003.tb02586.x
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  • 9
    Electronic Resource
    Electronic Resource
    Modeling Regional Ground-Water Flow in Fulton County, Indiana: Using the Analytic Element Method (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 30 (1992), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: In 1989, the Four County Landfill (FCL) in Fulton County, Indiana was closed by a federal judge because of regulatory violations and its threat to the environment. As part of the litigation, a ground-water flow modeling study was performed on behalf of a group of concerned citizens. Time constraints and, even more importantly, budgetary constraints called for an approach which could be implemented quickly and would yield meaningful results without additional field data acquisition. The modeling was performed with the relatively new analytic element method.The new method employs superposition of closed form analytic solutions, rather than a grid or element network, and proved an effective tool in answering some unresolved hydrogeological questions. The study results demonstrate substantially higher regional and local hydraulic conductivities than suggested by the landfill consultants, well-connected upper and lower aquifer zones at the site, and potential ground-water travel times from the landfill to the nearby Tippecanoe River of less than 15 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1992.tb01551.x
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  • 10
    Electronic Resource
    Electronic Resource
    Physical properties of pyrolytically sprayed tin-doped indium oxide coatings
    Amsterdam : Elsevier
    Thin Solid Films 205 (1991), S. 93-100 
    Details
    ISSN: 0040-6090
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0040-6090(91)90477-F
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