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  • 1
    Electronic Resource
    Electronic Resource
    A Simplified Analysis of Two-Well Tracer Tests in Stratified Aquifers (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 24 (1986), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: This paper illustrates several interesting effects of aquifer stratification on the results of two-well tracer tests by means of a simplified computer model. In the model, it is assumed that the aquifer is horizontal, confined, of constant thickness and porosity, and perfectly stratified in the vicinity of the test wells. The nonuniform advection pattern is taken into account in detail by the model, but the local hydrodynamic dispersion is completely neglected. This simplified model has been verified in part by comparisons with available analytical solutions valid for homogeneous aquifers and in part by comparisons with the results of a two-well field experiment of Pickens and Grisak (1981a) which was performed in a locally stratified aquifer. The applications of the model to several field situations with assumed values of the relevant parameters show that the concentration versus time breakthrough curve measured at the withdrawal well during a standard two-well test would be very sensitive to variations of the hydraulic conductivity in the vertical. Without the use of supplementary observation wells with isolated multilevel sampling points, the standard test would give little useful information about the hydraulic and dispersive characteristics of an aquifer. Factors such as the length of the tracer injection period, the use of recirculation and the physical size of the experiment all have a strong effect on the breakthrough curve measured at the withdrawal well, making the interpretation of field results difficult unless aquifer stratification is measured and properly taken into account.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1986.tb01460.x
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  • 2
    Electronic Resource
    Electronic Resource
    Laboratory Investigation and Analysis of a Ground-Water Flowmeter (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 23 (1985), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The ground-water flowmeter system, model 3OL, manufactured by K-V Associates Inc., Falmouth, Massachusetts was tested under controlled laboratory conditions. The influence of slotted pipe schedule, slot orientation, backfill materials, endcap bags, isolated regions of high hydraulic conductivity, and channelization near the slotted pipe wall was measured. The physical concept of the flow-meter in an ideal configuration was analyzed, and with the aid of an analytical model, the significance of the thermal and hydraulic characteristics of the aquifer and backfill materials is clarified. Results indicate that the basic instrument response is linear, consistent, and predictable qualitatively in a laboratory environment. Analysis and measurements show clearly that very small channelization around a slotted pipe casing or between the slotted pipe and the probe endcap can invalidate the instrument response. Additional potential complications arise due to unknown permeability contrasts between the aquifer matrix and the material used to backfill around the probe.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1985.tb01498.x
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  • 3
    Electronic Resource
    Electronic Resource
    Three-Dimensional Modeling of a Two-Well Tracer Test (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: A three-dimensional (3-D), advection-based numerical model has been developed for simulating two-well injection withdrawal tracer tests in heterogeneous granular aquifers, and the model has been applied to perform various simulations of an actual two-well tracer test conducted previously in a confined aquifer at a field site near Mobile, Alabama. Information obtained from a series of independent field tests is used as input in the model to account for the 3-D spatial distribution of the hydraulic conductivity (K) at the test site.The numerical model is based on a simplified, Lagrangian approach in which the transport of the tracer between the injection and withdrawal wells is modeled taking into account advection only. Processes such as dispersion, sorption, and chemical or biological reactions are neglected. Despite field data limitations and various simplifying assumptions, the model predictions of the withdrawal-well concentration breakthrough and of the mean tracer arrival times at various levels of two multilevel observation wells are in good overall agreement with the corresponding field observations.The results of this study indicate that it will be possible to construct realistic, predictive models of contaminant transport in heterogeneous granular aquifers if the necessary effort is made to obtain field measurements of the 3-D spatial distribution of hydraulic conductivity. The extent and feasibility of such an effort are expected to depend on the particular contamination problem at hand. Future research should be directed toward the problems of field measurement scale selection and the development of K distributions for models from sparse data sets.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1992.tb01578.x
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  • 4
    Electronic Resource
    Electronic Resource
    PERFORMANCE AND ANALYSIS OF AQUIFER TRACER TESTS WITH IMPLICATIONS FOR CONTAMINANT TRANSPORT MODELING–A PROJECT SUMMARY (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 25 (1987), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: The scale-dependence of dispersivity values used in contaminant transport models to estimate the spreading of contaminant plumes by hydrodynamic dispersion processes was investigated and found to be an artifact of conventional modeling approaches (especially, vertically averaged parameters in two-dimensional plume simulations). The work reported here shows that variations in hydraulic conductivity with depth result in significant variations in ground-water flow and contaminant transport velocities; it is the resulting velocity variations that, if vertically averaged, give rise to apparent scale-dependency of dispersion (e.g., increased dispersion with increasing travel distance). Special depth-selective observation well designs are recommended by the authors for use in tracer tests, so that detailed estimates of the variations in hydraulic conductivity, and flow and transport velocities can be obtained. Innovative modeling techniques that take advantage of the detailed information obtainable from such tests (by emphasizing advective transport, as opposed to dispersive transport), have been developed by the authors. These modeling techniques are shown to have an element of true predictive ability, being able to closely simulate actual results with little or no calibration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1987.tb02138.x
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  • 5
    Electronic Resource
    Electronic Resource
    DISCUSSION OF “A Radial Injection Tracer Experiment in a Confined Aquifer, Scarborough, Ontario, Canada” by Carl D. Palmer and Robert L. Nadon (1986)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 24 (1986), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1986.tb01680.x
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  • 6
    Electronic Resource
    Electronic Resource
    Multilevel Slug Tests with Comparisons to Tracer Data (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 29 (1991), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Multilevel slug tests were conducted in a confined, granular aquifer near Mobile, Alabama. Tracer injection and travel time experiments, more direct measurements of transport in the aquifer, were also conducted at the same location. The objective was to compare results of the two field investigations to ascertain the accuracy and utility of slug testing to measure transport properties of the aquifer. Nondimensional hydraulic conductivity profiles inferred from the slug tests and the tracer experiments were similar. The similarity of the profiles supported the utility of multilevel slug testing to characterize the hydraulic conductivity profile in the aquifer.The slug test data collected in three wells were interpreted using a radial flow model (Cooper et al., 1967) and a finite element model which considered both radial and vertical flow (Widdowson et al., 1989, 1990). Hydraulic conductivity values inferred from the measured data considering both radial and vertical flow were approximately two-thirds of the values inferred assuming radial flow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1991.tb00577.x
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  • 7
    Electronic Resource
    Electronic Resource
    Forced-Gradient Tracer Tests and Inferred Hydraulic Conductivity Distributions at the Mobile Site (1988)
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 26 (1988), S. 0 
    Details
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Four single-well tracer tests and a two-well tracer test performed in a 21-m thick confined granular aquifer at a field site near Mobile, Alabama, are described. The data from these tests together with previously published data from a single-well test and a two-well test allow one to begin to develop a three-dimensional picture of the hydraulic properties of the study aquifer. A consistent feature of all the tests is a high hydraulic conductivity zone which appears in the bottom third of the aquifer. This result is in agreement with hydraulic conductivity distributions inferred from previous aquifer thermal energy storage experiments at the same site. In some locations the new tests indicated high hydraulic conductivity zones in the upper third of the aquifer which were not detected in the previous two-well test and single-well tests performed at the same site but at different locations. Despite the three-dimensional spatial variations of hydraulic conductivity indicated by these tests, it was possible to predict the major features of the tracer concentration as a function of time at the withdrawal well in the two-well test by means of an available numerical model assuming perfect stratification at the test site and using a hydraulic conductivity distribution inferred from a single-well test.The apparent success of the model prediction presented here, as well as the success of a similar numerical simulation of the previous two-well test reported earlier, seem to support the conclusion that the study aquifer has an approximately stratified flow field at the test site. These field test results provide further evidence that reliable predictions of solute transport in a real aquifer will depend on a sufficiently detailed knowledged of the major features of the three-dimensional advection pattern in the aquifer. Based on this study and previous studies, it appears that a healthy mixture of viewpoints and techniques (geologic, hydrologic, geophysical, etc.) will be necessary to characterize the transport properties of natural ground-water systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1745-6584.1988.tb00790.x
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  • 8
    Electronic Resource
    Electronic Resource
    TheN=83 nucleus149Dy from Gamow-Teller decay of its 11/2− and 1/2+ 149Ho parents (1994)
    Springer
    The European physical journal 349 (1994), S. 13-24 
    Details
    ISSN: 1434-601X
    Keywords: 21.10.Pc ; 21.10.Re ; 23.20.Lv ; 23.40.Hc ; 27.60.tj
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A high-sensitivityγ-spectroscopic study of the149Hoπh 11/2 andπs 1/2 β-decays using mass separated sources has located dominant 0+ → 1+ GT decay strength associated with decay of pairedh 11/2 protons, leading to 3п-states in the149Dy daughter nucleus. In theirγ-decay low-lying149Dy levels characteristic of anN=83 nucleus are excited. They include theνf 7/2,νp 3/2,νh 9/2 andνp 1/2 single particle- and theνs 1 2/−1 andνd 3 2/−1 two-particle one-hole states, as well as the νf 7/2 × 3− andνf 7/2 × 2+ particle-phonon multiplets. A synopsis is given of these excitations in theN=83 isotones from149Nd to153Yb. The149Dy GT decay strength is discussed in terms of the147Tb82 and148Dy82 decays. The strength function results are also compared with independent149Ho 11/2− decay data from the literature based on totalγ-ray absorption measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01296328
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  • 9
    Electronic Resource
    Electronic Resource
    Elastic-plastic stress distribution in the rotating annular disk with variable thickness (1991)
    Springer
    Archive of applied mechanics 61 (1991), S. 548-554 
    Details
    ISSN: 1432-0681
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Übersicht Der ebene Spannungszustand in einem rotierenden Kreisring mit veränderlicher Dicke und aus Material mit linearer Verfestigung wird unter Zugrundelegung der Trescaschen Fließbedingung und der zugehörigen Fließregel untersucht.
    Notes: Summary The plane state of stress in a rotating annular disk with variable thickness is studied. The analysis is based on Tresca's yield condition, its associated flow rule and linear strain hardening.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00786968
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  • 10
    Electronic Resource
    Electronic Resource
    Chemical etching for fine-grained YBa2Cu3O7-x (1993)
    Springer
    Journal of materials science 12 (1993), S. 1080-1082 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00420527
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