摘要:

Experimental and theoretical studies of time dependence of the magnetisation are described. The time dependence phenomenon has its origins in thermally activated transitions over energy barriers and is strongly affected by interaction effects. Studies of particulate recording media and thin films are described which give interesting insight into the behaviour of the systems. Consideration is also given to the practical problem of the frequency dependence of the coercivity in particulate recording media which has implications from the point of view of the evaluation of the materials.

ISSN:1058-9759    

DOI:10.1080/02780899108953122

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

We describe a thermal wave imaging system based on gas-microphone detection of the harmonic component of the photoacoustic (PA) signal. In this system the sample is excited by a laser beam modulated at a frequency ƒ and the detection of the associated thermal wave field is carried out at a frequency 2ƒ. The technique demonstrates lateral resolution comparable to conventional thermal wave systems based on detection of the fundamental component of thePAsignal, but provides for better contrast in depth-profiling applications.

ISSN:1058-9759    

DOI:10.1080/02780899108953123

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

A testing method is described for the depth measurement of defects that can occur in CANDU nuclear reactor pressure tubes. Experiments are reported which use immersion transducers, to study the interaction of shear waves with both artificial and real defects. A hybrid system, based on both time and amplitude measurements, is proposed for the estimation of defect depth.

ISSN:1058-9759    

DOI:10.1080/02780899108953124

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

摘要:

The application of high frequency dielectric measurements to the examination of adhesively bonded structures is described. The use of the frequency dependence of the real and imaginary parts of the complex permittivity for the identification of water ingress into a bonded structure is discussed. Pulse measurements allow identification of the spacial distribution of impedance changes in the bond and allow identification of voids and also non bonded areas in new as well as aged bonds. The paper considers the scope of the method for the NDT examination of new and aged adhesively bonded structures.

ISSN:1058-9759    

DOI:10.1080/02780899108953125

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor

ISSN:1058-9759    

DOI:10.1080/02780899108953126

出版商:Taylor & Francis Group    

年代:1991

数据来源: Taylor