Electrical detection of leaks in lined waste disposal ponds

Geophysics ◽  
1997 ◽  
Vol 62 (6) ◽  
pp. 1737-1744 ◽  
Author(s):  
William Frangos
Keyword(s):  
Waste Disposal ◽  
Current Source ◽  
Nonlinear Inversion ◽  
Blind Test ◽  
Location Accuracy ◽  
Electrical Potentials ◽  
Practical Concern ◽  
Plastic Liner ◽  
A Site ◽  
Processing Steps

A method for detecting and locating leaks in the plastic liner of a waste disposal pond has been implemented and tested at a site near Budmerice in Slovakia. The method is based on detecting electric current flowing through holes in the insulating lining membrane. Unlike similar methods employed elsewhere, this implementation allows monitoring for leaks that may develop during and after filling the pond with electrically inhomogeneous solid waste. To accomplish this goal, sensing electrodes were placed below the membrane during construction. In operation, current was passed between an electrode inside the pond and another outside; the voltage caused by this current was observed on the buried sensing electrodes. The data were then processed to detect and locate any leaks in the membrane. An important practical concern is achieving acceptable detectability and location accuracy while using a sufficiently sparse grid of sensing electrodes. This problem was overcome by two processing steps: (1) calculating electrical potentials from the observed voltages and (2) performing a nonlinear inversion on subsets of the data. With this technique, observations made with a 10- × 8-m grid of electrodes, a relatively low‐power current source, and a simple receiver can provide accurate location information, even for small leaks. In a blind test, the system accurately predicted the locations of six leaks that were subsequently verified visually. Five of the leaks were cuts in the plastic typically measuring less than 2 × 0.1 cm, whereas the sixth leak was a group of many small holes. For the five, the typical location accuracy was about 30 cm, comparable to the basic survey location accuracy of the sensing electrodes.

Predictability of strong motions from the Northridge, California, earthquake

1996 ◽  
Vol 86 (1B) ◽  
pp. S100-S114 ◽  
Author(s):  
John G. Anderson ◽  
Guang Yu
Keyword(s):  
Vertical Component ◽  
Source Model ◽  
Statistical Characteristics ◽  
Peak Acceleration ◽  
Blind Test ◽  
Peak Displacement ◽  
Velocity Models ◽  
Maximum Bias ◽  
Standard Deviations ◽  
A Site

Abstract The composite source model for generating synthetic strong ground motions is tested for its ability to predict the statistical characteristics of Northridge accelerograms recorded in or adjacent to the San Fernando valley. The general problem is prediction of strong motions at a site of engineering interest with sufficient realism to be useful for engineering applications. The strongest test of any proposed method is a blind prediction. For this study, a completely blind test was not possible. Our objective was to use only a preliminary description of fault geometry and magnitude and previously published velocity models and, without iteration to improve the quality of fit, to evaluate the differences between predicted and observed accelerograms. The parameters that we predict are peak acceleration, peak velocity, peak displacement, Fourier spectra at seven frequencies, and pseudorelative velocity response (5% damping) at seven periods. Our results are given for 14 stations. For the horizontal components, these parameters are all predicted with a maximum bias of under 50% and an average bias of observations exceeding predictions by 6%. For peak acceleration and some response spectral periods, the bias for this model is smaller than at least some regressions, when applied to this specific earthquake. On the vertical component, the maximum bias is a factor of 2, and the average gives predictions exceeding observations by 25%. Standard deviations of the common logarithm of the ratio of observed-to-predicted parameters are typically about 0.3, which is perhaps 50% greater than the standard deviations typical of regressions but comparable to standard deviations of observations from this earthquake compared to regressions. In the future, it is likely that, in some cases, traditional regressions will be replaced with synthetic calculations of some type, such as the method used here. Based on the results of this study, the amount of progress that has been made in obtaining that goal is very encouraging.

The Difficulties of Undertaking Site Characterisation on Operational Nuclear Licensed Sites

2003 ◽  
Author(s):  
Peter Booth ◽  
Robert Gordon
Keyword(s):  
Waste Disposal ◽  
Monitoring Network ◽  
Sampling Strategy ◽  
Site Investigation ◽  
Technical Requirements ◽  
Fit For Purpose ◽  
Safety Cases ◽  
Site Characterisation ◽  
A Site ◽  
Ground Contamination

Undertaking site investigation on nuclear licensed sites is very different to site investigation on other sites, even those which are heavily contaminated. This paper sets out to highlight some of the issues which need to be considered when formulating a fit for purpose, yet defensible site characterisation programme on such a site. The first and most important aspect of the work is to set out clearly your objectives. There may be a number of reasons why a site investigation is being undertaken. These could include purely fulfilling your site licence conditions as an operator or they could be more specific like supporting a defined de-licensing or decommissioning project, installing a monitoring network, or determining the extent of ground contamination. Ensuring that a conceptual model exists is the next step, even if only at a preliminary stage, as this coupled with the desk study will help formulate the site characterisation programme. Logistical issues as well as technical requirements need to be factored in, but in order to maintain transparency it is important to declare the latter first. Like other sites with ground contamination, issues like sampling and analysis need to be considered. Clearance procedures on nuclear licensed sites are extremely stringent and can lead to delays. These need to be considered, especially if sending samples offsite for organics analysis. The laboratories themselves need to be licensed to handle radioactive samples and the transport regulations also need to be adhered to. Other logistical issues requiring consideration include safety cases, plant modification proposals and waste disposal. The technical side itself sets its own challenges in that decisions need to be closely linked into the logistics. Will the samples and data be collected primarily through intrusive techniques or is there a requirement to utilise non-intrusive methodology? How do you defend the proposed site sampling strategy when you have access restrictions? Do you need to have permanent monitoring facilities? These are just some of the questions which need to be answered if a site operator is to have a transparent and defensive site investigation programme on a nuclear licensed site.

Emergence of Radial Nerve Dominance in Median Nerve Cortex After Median Nerve Transection in an Adult Squirrel Monkey

1997 ◽  
Vol 77 (1) ◽  
pp. 522-526 ◽  
Author(s):  
C. E. Schroeder ◽  
S. Seto ◽  
P. E. Garraghty
Keyword(s):  
Median Nerve ◽  
Squirrel Monkey ◽  
Ulnar Nerve ◽  
Action Potentials ◽  
Radial Nerve ◽  
Current Source ◽  
Short Latency ◽  
Nerve Transection ◽  
A Site ◽  
Stimulation Of

Schroeder, C. E., S. Seto, and P. E. Garraghty. Emergence of radial nerve dominance in median nerve cortex after median nerve transection in an adult squirrel monkey. J. Neurophysiol. 77: 522–526, 1997. Throughout the glabrous representation in Area 3b, electrical stimulation of the dominant (median or ulnar) input produces robust, short-latency excitation, evident as a net extracellular “sink” in the Lamina 4 current source density (CSD) accompanied by action potentials. Stimulation of the collocated nondominant (radial nerve) input produces a subtle short-latency response in the Lamina 4 CSD unaccompanied by action potentials and followed by a clear excitatory response 12–15 ms later. Laminar response profiles for both inputs have a “feedforward” pattern, with initial activation in Lamina 4, followed by extragranular laminae. Such corepresentation of nondominant radial nerve inputs with the dominant (median or ulnar nerve) inputs in the glabrous hand surface representation provides a likely mechanism for reorganization after median nerve section in adult primates. To investigate this, we conducted repeated recordings using an implanted linear multi-electrode array straddling the cortical laminae at a site in “median nerve cortex” (i.e., at a site with a cutaneous receptive field on the volar surface of D2 and thus with its dominant afferent input conveyed by the median nerve) in an adult squirrel monkey. We characterized the baseline responses to median, radial, and ulnar nerve stimulation. We then cut the median nerve and semi-chronically monitored radial nerve, ulnar nerve and median nerve (proximal stump) evoked responses. The radial nerve response in median nerve cortex changed progressively during the weeks after median nerve transection, ultimately assuming the characteristics of the dominant nerve profile. During this time, median, and ulnar nerve profiles displayed little or no change.

Dual effects of amphotericin B on ion permeation in toad urinary bladder epithelium

1978 ◽  
Vol 235 (5) ◽  
pp. F507-F514
Author(s):  
L. Reuss ◽  
J. T. Gatzy ◽  
A. L. Finn
Keyword(s):  
Urinary Bladder ◽  
Cell Membrane ◽  
Amphotericin B ◽  
Toad Urinary Bladder ◽  
Bladder Epithelium ◽  
Electrical Potentials ◽  
A Cell ◽  
A Site ◽  
Microelectrode Measurements ◽  
Toad Urinary Bladder Epithelium

The mechanisms of action of amphotericin B on the electrical properties of the toad urinary bladder epithelium were studied with microelectrode techniques. Cell membrane and transepithelial electrical potentials and resistances were measured in the absence and in the presence of the drug during exposure to bathing mediums of different ionic compositions. As observed previously by other investigators, amphotericin B produces a dramatic decrease of transepithelial electrical resistance (Rt) and an increase of the rate of sodium transport. Our results indicate that the effect of the drug on Rt depends in part on an increase in Na conductance across the luminal cell membrane (amiloride-insensitive), but is caused mainly by an increase of ionic conductances (with the sequence GK greater than GNa greater than G choline greater than GCI) at a site in parallel with the impaled cells (i.e., across a cell type not investigated by the microelectrode measurements or across the paracellular pathway.

Before Infrastructure: The Poetics of Paving in John Gay's Trivia

PMLA ◽  
2017 ◽  
Vol 132 (5) ◽  
pp. 1134-1148 ◽  
Author(s):  
David Alff
Keyword(s):  
Eighteenth Century ◽  
Early Modern ◽  
Waste Disposal ◽  
Critical Inquiry ◽  
John Gay ◽  
Modern Idea ◽  
A Site ◽  
The City

Infrastructuralism denotes an emerging field of critical inquiry dedicated to understanding the facilities, equipment, and personnel that deliver civilization's most basic amenities, including water, light, heat, waste disposal, and transportation. How did writers portray infrastructure before it became a word and concept? In his 1716 mock-georgic poem Trivia; or, The Art of Walking the Streets of London, John Gay depicted one element of eighteenth-century society's built underpinnings, the street, as an assemblage of decaying but reparable matter, a site for disparately institutionalized forms of labor, and an array of moral and navigational possibilities called ways. Listening to Trivia's representation of road making can yield both an early modern idea of the city as object of upkeep and a historicized poetics of infrastructure able to make meaning of civic enterprise present and past.

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