Development of a Combined Quantity and Quality Model for Optimal Management of Unsteady Groundwater Flow Fields

Presented are alternative techniques for including conservative solute transport within computer models for optimizing groundwater extraction rates. Unsteady two-dimensional flow and dispersed conservative solute transport are assumed. Comparisons are made of the practicality of including modified forms of implicit and explicit finite difference solute transport equations within optimization models. These equations can be calibrated and subsequently used within a MODCON procedure. The MODCON modelling procedure consists of an integrated series of five optimization or simulation modules. The procedure is applicable for either an entire aquifer system or for a subsystem of a larger system. The first module, A, computes physically feasible recharge rates across the boundaries of the modelled subsystem. Module B computes optimal extraction rates without considering groundwater quality. Module C uses method of characteristics simulation to compute solute transport that would result from implementing the pumping strategy of model B. Module D uses linear goal programming and nonlinear solute transport equations to calibrate linear coefficients. It attempts to duplicate the solute transport predicted by module C. Calibration is performed because coarsely discretized implicit or explicit solute transport equations may not be as accurate as the method of characteristics. Module E includes appropriate calibrated equations of module D as well as the flow equations of module B. It computes an optimal pumping (extraction or recharge) strategy that can satisfy future groundwater contaminant concentration criteria. Testing of the validity of this optimal pumping strategy is subsequently accomplished using module C. If necessary, one may cycle through modules C, D and E until convergence is obtained--until concentrations resulting from implementing the strategy of E are demonstrated to be acceptable

Development of a Combined Quanity and Quality Model for Optimal Groundwater Management

Presented is a procedure for incorporating solute transport as linear constraints within computer models for optimizing regional groundwater extraction strategies. The MODCON modelling procedure uses linear goal programming, embedded linearized equations for flow and solute transport and a MOC simulation model. Assumed is 2D flow and solute transport and a dispersed conservative contaminant. The MODCON procedure develops steady groundwater extraction strategies that will satisfy future groundwater quality constraints while simultaneously causing future piezometric heads to be as close to current heads as possible. The procedure is applied to a 160 square mile area in southeastern Arkansas

EXEIS, Expert screening and optimal extraction/injection pumping systems for short-term plume immobilization

This report presents the EXEIS family of micro-computer based programs for achieving short-term contaminant plume containment. EXEIS is applicable if contaminated water cannot be extracted and water cannot be imported to or exported from the site. There are two main purposes and types of users. For persons relatively unfamiliar with groundwater remedial actions, an expert screening system gives guidance concerning whether extraction/injection (Eli) pumping, slurry wall or sheet piling are most appropriate. For personal more experienced in remedial actions, management models compute optimal E/I strategies for short-term containment. Via deterministic and stochastic multiobjective optimization models, uncertainty in both planning horizon and aquifer parameters is addressed

Optimal piezometric surface management for groundwater contaminant control

A methodology is described for efficiently evaluating possible injection/extraction pumping schemes to most economically contain a groundwater contaminant plume. A multi-objective model is analyzed with a micro-computer. Simulation and optimization is performed by employing the response matrix method

Superfluid turbulence and pulsar glitch statistics

Experimental evidence is reviewed for the existence of superfluid turbulence in a differentially rotating, spherical shell at high Reynolds numbers (\Rey\gsim 10^3), such as the outer core of a neutron star. It is shown that torque variability increases with \Rey, suggesting that glitch activity in radio pulsars may be a function of \Rey as well. The \Rey distribution of the 67 glitching radio pulsars with characteristic ages $\tau_c \leq 10^6$ {\rm yr} is constructed from radio timing data and cooling curves and compared with the \Rey distribution of all 348 known pulsars with $\tau_c \leq 10^6$ {\rm yr}. The two distributions are different, with a Kolmogorov-Smirnov probability $\geq 1 - 3.9 \times 10^{-3}$. The conclusion holds for (modified) Urca and nonstandard cooling, and for Newtonian and superfluid viscosities

Expert potentiometric surface modification for groundwater contaminant management

An expert system is linked to an previously reported optimization program. The expert system prompts the user for information about a groundwater contamination problem. The expert system determines whether pumping is a suitable containment strategy. If appropriate. it selects several well arrangements to be evaluated by an optimization algorithm

Gravitational radiation from pulsar glitches

The nonaxisymmetric Ekman flow excited inside a neutron star following a rotational glitch is calculated analytically including stratification and compressibility. For the largest glitches, the gravitational wave strain produced by the hydrodynamic mass quadrupole moment approaches the sensitivity range of advanced long-baseline interferometers. It is shown that the viscosity, compressibility, and orientation of the star can be inferred in principle from the width and amplitude ratios of the Fourier peaks (at the spin frequency and its first harmonic) observed in the gravitational wave spectrum in the plus and cross polarizations. These transport coefficients constrain the equation of state of bulk nuclear matter, because they depend sensitively on the degree of superfluidity.Comment: 28 page

Maximizing sustainable ground-water withdrawals: comparing accuracy and computational requirements for steady-state and transient digital modeling approaches

Rigorous models for maximizing sustainable groundwater withdrawals may require more computer memory for their constraint set than is available. In some situations, alternative constraint formulations yield similar or identical answers resulting in great saving in computer memory requirements. In order to evaluate the efficiency of using alternative constraints1 maximum ground-water withdrawal pumping strategies were computed by three digital models for a hypothetical area for a five-decade period. Model A maximized steady ground-water withdrawal. Model B maximized unsteady ground-water mining. Model C maximized unsteady ground-water mining subject to a constraint that final pumping be sustainable after the end of the 50-year period. Change in pumping with time was forced to be monotonic (variably increasing or decreasing but not oscillating) in time. The models were tested by assuming constant transmissivity and by using a range of recharge constraints for four scenarios with stressed and unstressed initial potentiometric surfaces and with constant and changing upper limits on pumping. In situations where upper limits on pumping changed with time, Model A was run repetitively, by using monotonicity constraints. In -those situations, optimality of solution is not assured in all cells. Models A and C computed pumping strategies sustainable after the end of the 50-year period. Model C was the most detailed in that it allowed pumping to vary in time and recharge constraints were based both on unsteady-state flow at 50 years and on steady flow after that time. Model A considered only steady pumping and recharge constraints. Pumping strategies from Model B were not necessarily sustainable because it considered only recharge constraints at 50 years. Results indicate that, when recharge through the study area periphery is unconstrained, all models compute identical pumping. For an initially undeveloped aquifer, or for a developed aquifer if steady pumping is assumed, Model A computes strategies very similar to those computed with Model C and requires only 28 percent of the computer memory and 38 percent of the execution time. For an initially overdeveloped aquifer, Model B computes identical pumping strategies to those computed with Model C and requires 73 percent of the computer memory and 78 percent of the computation time. For that situation, Model A is more conservative and computes less pumping than Model C if pumping in Model C is permitted to vary. Although Model A may compute lower pumping rates during the first 50 years, the sustainable pumping rate thereafter may be greater for Model A than for Model C

The black hake fishery in the Mauritanian EEZ: Analysis of the possible application of a 30 cm minimum

The fishery of black hake Merluccius spp. in the Mauritanian EEZ mainly comprises a Spanish trawler fleet, as well as some longliners. The highly specialised trawling fishery has diminished its effort, while its annual landings have remained stable, not surpassing 12 000 t. In the total annual catch, individuals measuring less than 30 cm do not represent more than 10% (with the exceptions of 1992 and 1993, when the highest recruitment was recorded), although this percentage is higher during the cold season. The evolution of both the yields and the average sizes of the landed hakes, which have increased since 1991, do not indicate an overexploited resource, especially if we take into account that the potential for hake exploitation off Mauritania has been estimated at 133000 tons annually. The implementation of a minimum legal length of 30 cm for Merluccius spp., which is contemplated in Mauritanian fishing regulations, would contradict the conditions of the present fishing agreement, which imposes a 60 mm mesh size and prohibits fishing within an offshore limit of 18 nautical miles. Due to mesh selectivity, to black hakes ' size-segregation with depth, and to the biological characteristics o f these species, which are small and highly migratory, Spanish trawlers will continue to catch individuals under 30 cm. Therefore, regulation by means of minimum size would not be an adequate conservation measure for black hakes in the Mauritanian EEZ.La pesquería de merluzas negras Merluccius spp. es ejercida en la ZEE mauritana por una flota española de arrastreros y por algunos palangreros, La pesquería de arrastre, altamente especializada, ha disminuido su esfuerzo, mientras sus capturas se han mantenido, no superando las 12 000 toneladas anuales. Aunque con valores mensuales mas elevados durante la estación fría, los ejemplares menores de 30 cm sólo han representado más del 10 % del total anual en 1992 y 1993, años de fuerte reclutamiento. La evolución de los rendimientos y de las tallas medias de las merluzas desembarcadas, que han aumentado desde 1991, no muestran una sobrexplotación del recurso, sobre todo si tenemos en cuenta que su potencial extraíble ha sido estimado en aguas mauritanas en 133000 toneladas anuales. La aplicación de la talla mínima de 30 cm contemplada por la legislación mauritana a Merluccius spp. entraría en contradicción con las condiciones del acuerdo de pesca vigente, que impone la malla de 60 mm y autoriza la pesca fuera de las 18 millas marinas. Debido a la selectividad de la malla, a la segregación de tallas con la profundidad que presentan las merluzas negras y a las características biológicas de estas especies, de pequeño tamaño y altamente migratorias, los arrastreros españoles seguirán capturando ejemplares menores de 30 cm. La regulación mediante la talla mínima no será, por consiguiente, una medida de conservación para las merluzas negras en la ZEE mauritana.Versión del editor0,000

Electron Beam Adjustment in PLATO RTS 2 Including the Effect of Air Gaps

Background and Purpose: Beam characterization for electron dose calculations in PLATO RTS 2 treatment planning system requires the tuning of two adjustment parameters: sqx (the initial angular spread) and FMCS (a "fudge" multiple Coulomb scattering parameter). This work provides a set of suggestions to optimise electron dose calculations with PLATO, taking into account the effect of air gaps between the electron applicator and the patient skin. Material and Methods: Two adjustment criteria have been followed: one which uses just one input data set corresponding to the standard (null) air gap and another one that takes into account the whole range of clinically used distances between the electron applicator and the patient surface. The adjusted values of sqx were compared with experimental data and GEANT3 Monte Carlo code results. A systematic study has been carried out of the effect of both adjustment parameters on electron dose calculations in water. Comparisons of dose distributions and point dose values have been done between PLATO RTS2, GEANT3 Monte Carlo code and experimental data. Also the dependence on field size has been assessed. The values of sqx for the different electron energies obtained through the different approaches are discussed. Results and conclusions: The first adjustment criteria yield unrealistic dose distributions whenever the air gap is different from the standard one. A sqx balanced with a proper FMCS parameter leads to reasonably good dose distributions and point dose values that agree with experimental results within less than 1%