ISSN:1058-9759    

DOI:10.1080/10589759408956405

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

An introduction to the physical background of the various aspects and commonly encountered terminology encountered in NMR experiments is presented. Illustrations using selected examples are given of contributions NMR techniques already make to the field of non-destructive testing and evaluation.

ISSN:1058-9759    

DOI:10.1080/10589759408956406

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

In many applications of magnetic resonance imaging large linewidths means that to achieve useful resolution in the image large magnetic field gradients should be employed. This paper outlines the principles of stray field imaging that utilises the large gradients intrinsic to the fringe field of superconducting solenoidal magnets. Examples of images from strongly broadened everyday objects are given.

ISSN:1058-9759    

DOI:10.1080/10589759408956407

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

A new method to determine pore dimensions in the mesopore range is described. NMR is used to quantify the melting point depression of an absorbed liquid and hence determine pore size distributions in various silica samples. Results are shown to compare well with conventional gas desorption determinations and ultimate resolution considered. The method is relatively simple, rapid and non-destructive. The damage to pore structures caused by ice formation is demonstrated using the technique.

ISSN:1058-9759    

DOI:10.1080/10589759408956408

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

Nuclear Magnetic Resonance Microscopy (NMRM) images were obtained of a cell of sintered silica (with original grain diameters of 250 to 500 μm) that was initially flooded with water and subsequently with both water and oil. The first acquisition was non-selective and revealed the combined spatial distribution of the water and oil phases. Two subsequent acquisitions, at identical locations, imaged the water and oil phases separately. Each acquisition comprises 16 images with a matrix of 256 by 256 pixels in a square Field of View, FOV, of 1.15 cm, and each image refers to a slice thickness of 100 microns. Volume rendering techniques applied to the image data enable the visualization of the 3D connectivity of the fluid phases in the porous medium. Stereology provides the means by which numerical descriptions of properties of these phases can be efficiently obtained free from model based assumptions, and with known precision. Accordingly, estimates were obtained of the porosity, surface area per unit volume, number per unit volume and mean volume of the ‘regions’ of water and oil within the cell. The overall porosity is estimated as 36.1% (Coefficient of Error, CE, = 3.6%) with oil and water present in the ratio 1.00 to 1.15. At the resolution of the experiment, the water surface measures approximately 2.5 times greater than the oil surface within the cell. There are seven times more ‘regions’ of water than oil with respective mean volumes of 0.03 mm3(Coefficient of Variation, CV, = 19%) and 0.20 mm3(CV = 64%).

ISSN:1058-9759    

DOI:10.1080/10589759408956409

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The application of NMR methods to the non-destructive testing of thermoplastic composites is discussed. NMR imaging of the polymer matrix is restricted to the detection of defects in excess of 5 mm using standard instrumentation. Higher resolution can be achieved by imaging the matrix at high temperatures or by more sophisticated NMR procedures with the practical limit of 0.1 mm or so at present. Composites subject to high fluid exposure during their working life can be examined by NMR imaging of fluid absorbed by the composite which tends to collect in the defect, as illustrated by water in a canine APC2 hip joint. Polymer morphology can be studied using NMR relaxation times but the localised measurement of these features is hindered by the sensitivity of the pulse sequences to inhomogeneities in the radiofrequency across the field of view.

ISSN:1058-9759    

DOI:10.1080/10589759408956410

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor

摘要:

The range of NMR instruments designed for industrial and other specialised applications are reviewed. This covers both steady state and transient (pulsed) NMR for the measurement of both stationary and flowing materials. Areas covered include sample consideration, magnet design, RF power requirements, probe design and transmit-receive circuits.

ISSN:1058-9759    

DOI:10.1080/10589759408956411

出版商:Taylor & Francis Group    

年代:1994

数据来源: Taylor