Ground zero project development in Burma : appropriating the future through history, identity, and imagination in assessment

unavailabl

Electromagnetic Sensor Arrays— Experimental Studies

The objectives of this research program are to develop the theoretical models, design methodology, and technology needed for the optimum application of near-field electromagnetic sensor arrays in NDE and robot control. A basic requirement for this work is to be able to analyze and control the spatial-frequency content in the field configuration generated by the array. To aid in understanding how best to satisfy this requirement, initial efforts at SRI have focused on obtaining experimental measurements of the relative spatial distributions associated with the responses of eddy-current reflection probes to surface steps and surface-breaking rectangular slots in aluminum plates. This paper presents the results obtained using a commercial reflection probe (Nortec SPO-2065) and an SRI-constructed five-coil, air-core reflection probe to interrogate such surface discontinuities. The data obtained with the five-coil probe are then compared with the results of a theory for the spatial response of such a probe that has been developed at Stanford University [1]

Microwave Eddy-Current Techniques for Quantitative NDE

The objectives of this work are to develop an electromagnetic scattering model that can be used to predict the scattering from a crack in a conducting surface and to evaluate the feasibility of using this model in conjunction with microwave-measurement techniques to determine the dimensions of such a crack. Such a theory has been developed, and its derivation is presented. Theory and experiment are compared for rectangular slots measured at 100 GHz, and the agreement is found to be good. The necessary measurement protocol for determining the dimensions of a crack is discussed, and an example of inverting the measured data to determine the dimensions of a rectangular slot is presented

Microwave Techniques for NDE of Ceramics

In recent years, the technology for generating and controlling electromagnetic energy at frequencies of 100 GHz and above has improved considerably, and such components are now readily available. In view of this fact, we have undertaken a program to assess the applicability of this technology to the NDE of ceramic materials and components. We have found that Si3N4 is nearly transparent at these high frequencies, which permits the interior of components made from this material to be inspected using microwave energy. The dielectric constant of hot-pressed Si3N4 is about 7.5, so the wavelength in this material at 100 GHz is about 1mm. This electromagnetic wavelength is comparable to the acoustic wavelength of 10 MHz ultrasound in this material. Thus, microwave C-scan images will have resolutions roughly comparable to those produced by commercial ultrasonic equipment, but do not require the use of a water bath or other coupling medium in order to achieve rapid scanning. In addition, electromagnetic and ultrasonic scattering will differ for a given flaw, and thus microwave imaging may provide better flaw discrimination in some cases

Quantitative detection of atropine-delayed gastric emptying in the horse by the ¹³C-octanoic acid breath test

The <sup>13</sup>C-octanoic acid breath test has been correlated significantly to radioscintigraphy for measurement of gastric emptying indices in healthy horses. The objective of this study was to investigate the validity of the test for measurement of equine delayed gastric emptying, prior to its potential clinical application for this purpose. A model of atropine- induced gastroparesis was used. Gastric emptying rate was measured twice in 8 horses using concurrent radioscintigraphy and/or breath test after treatment i.v. with either atropine (0.035 mg/kg bwt) or saline in randomised order. Analysis of both data sets demonstrated that the atropine treatment had caused a significant delay in gastric emptying rate. Paired breath test data showed an atropine-induced delay in gastric half-emptying time t(1/2)), with no overlap in the 99% Cl range (P<0.001). Significant correlations were found between scintigraphy and <sup>13</sup>C-octanoic acid breath test for calculation of both t(1/2) (P<0.01) and lag phase duration (P<0.05) in the atropine-delayed emptying results. The mean (s.d.) bias in breath test t(1/2) when compared with scintigraphy was 1.78 (0.58) h. The results demonstrated that the <sup>13</sup>C-octanoic acid breath test was an effective diagnostic modality for the measurement of equine delayed gastric emptying. The technique offers advantages to existing methods for clinical investigation, as it is noninvasive, not radioactive, quantitative and requires minimal equipment or training to perform