摘要:

Many techniques have been established that perform tomographic reconstructions of the acoustic velocity profile of a solid object. A SIRT technique was selected as a particular one that was able to handle arbitrary sampling geometries and to incorporate a raybending correction. In this paper, these modifications to the basic algorithm are presented. A fast approximate raybending correction, suitable for use on personal computers, is given based on discretization of the raypaths, and the use of a graph-searching algorithm to obtain the minimum time path. The performance of the algorithm is evaluated in the field of seismic frequencies, imaging an area of backfill in an irregularly shaped rock pillar in a hard rock mine.

ISSN:1058-9759    

DOI:10.1080/10589759108953135

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

At the end of 1988 a research project was started to develop a practical, high-resolution imaging method for ultrasonic NDI, based on the Synthetic Aperture Focusing Technique (SAFT). This project was initiated by the TNO Institute of Applied Physics and two major companies in The Netherlands. As conventional single-transducer measurements do not provide enough ultrasonic information on different types of defects, one is forced to make use of separate sources and receivers. The tandem configuration, where both source and receiver (separated by some distance) are scanned, is capable of producing useful measurements, but the application of two moving transducers makes the tandem set-up generally too complicated in practice. The single-transducer LLT-technique (Walte, Gebhardt,et al. [1]) is also very well applicable for imaging in practice. However, for this technique, which utilizes indirectly reflected and mode-converted waves, the imaging zone is very limited.

ISSN:1058-9759    

DOI:10.1080/10589759108953136

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The development of Ground Probing Radar (GPR) in the investigation of masonry arch bridge systems has been restricted due to the requirement of specialist interpretation of the data. There is therefore a need for a method of simulation which aids the interpretation of GPR surveys. The method of convolution allows rapid simulation of varying geometries and material properties to be investigated. The combination of digital GPR systems along with simulation software will help a better engineering assessment to be made of the many masonry arch bridge systems now under review in the UK at the present time.

ISSN:1058-9759    

DOI:10.1080/10589759108953137

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:1058-9759    

DOI:10.1080/10589759108953138

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor