Surface pulse

When the alkane molecules are tr ped in the pores of a zeolite, much stronger energetic interactions occur compared to those on amorphous surfaces. Pulse chromatographic experiments in liquid phase showed a slight increase of the alkane retention with carbon number on a column packed with a large pore Y zeolite [5]. When ZSM-S was used, a zeolite with much smaller pores than Y, very large differences in adsorption between short and long alkanes were observed in liquid phase. 

Fig. II.2.6 Normal pulse voltammograms at a hanging mercury drop electrode in 5 x 10 M imidazoacridinone (substrate adsorbs at electrode surface). Pulse time a 2, b 5, c 10, d 25, e 50, and/100 ms. Instrumental drop time 1 s. (Adapted from [8] with permission)...

More conveniently, use the back surface pulse echo... 

The responses in Fig. 3.8 are calibrated results by two methods of the sensor calibration. One is a calibration method by NIST, as illustrated in Fig. 3.10 (Breckenridge 1982). A large steel block of 90 cm diameter and 43 cm deep was employed. As a step-function impulse, a glass capillary source was employed, and elastic waves were detected by a capacitive transducer and by a sensor under test. The calibration curve was obtained as a ratio of the response of the sensor to that of the eapacitive transducer. The capacitive transducer (sensor) could record a Lamb s solution due to surface pulse as discussed in Chapter 7. It is reasonably assumed that the capacitive transducer detect the vertical displacement at the surface due to a step-function force. The other is known as a reciprocity method, which Hatano and Watanabe (Hatano Watanabe 1997) suggested to use, and confirmed an agreement with the NIST methods. As seen in Fig. 3.8, it is demonstrated that both method can provide similar calibration curves. 

Breckenridge FR (1982) Acoustic emission transducer calibration by means of the seismic surface pulse. J. Acoustic Emission 1(2) 87-94... 

Perkeris CL (1955) The seismic surface pulse. Proc. Natl. Acad. Sci. 41 469-480... 

In elastodynamics as well as in seismology, the problem where a force is applied in a half space is called Lamb s problem. This is because the problem was first solved by Lamb [1904]. Then, Pekeris published famous results of Lamb s solutions due to a surface pulse (Pekeris 1955) and a buried pulse (Pekeris 1955). 

Fig. 7.1. Surface pulse f 3(1) and buried pulse f 3(t) in a half space.

The configuration of the detection is illustrated in Fig. 7.1, showing two cases. One is the case of buried pulse (force)/sft), and the other is that of surface pulse, fsft). As published by Pekeris (Pekeris 1955), these two forces result in the completely different displacement fields at point x. In Fig. 7.2, examples of Lamb s solutions due to a buried step-function force, where/sO) = hsft), are given. The depth of the source, D, is 6 cm and the horizontal distance, R, is varied as 3 cm, 6 cm and 9 cm. Here P-wave velocity Vp is assumed as 4000 m/s and Poisson s ratio is 0.2. These material properties actually represent those of concrete. Near the epicenter, only P-wave and S-wave are observed as shown in Fig. 7.2 (a). 

As discussed in Chapter 3, Breckenridge et al. [1981] developed a capacitance-type sensor of very flat response, by which they detected AE waves due to a break of glass capillary shown in Fig. 7.4. Later, the capillary break was replaced by the pencil-lead break by Hsu [1978]. As compared Fig. 7.3 with Fig. 7.4, first time, they showed that AE wave detected by the flat-type sensor due to the step-function force is actually identical to Lamb s solution due to the surface pulse. It was also demonstrated that Lamb s solution due to a buried pulse could be obtained by applying the force at the bottom of the block in Fig. 3.10. Thus, it is clarified by them that the displacement observed by the flat-type sensor due to capillary break or pencil-lead break is identical to G 33(x,yo,t). This implies that Green s function of the specimen can be empirically obtained by just applying the pencil-lead break and recording the displacements. 

By employing a concrete block as shown in Fig. 7.5, AE waves due to surface pulse is detected at the point E. In Fig. 7.6 (a), AE wave detected by AE sensor of resonance frequency 1 MHz is shown, where the force was applied by the same-type sensor driving an electric pulse at the distance R = 6 cm. In this case, the source-time function f(t) was reasonably assumed (Ohtsu 1982),... 

Fig. 7.12. Source-time functions df(t)/dt by deconvolution analysis of Lamb s problem due to a surface pulse. The solid curve is analyzed and the broken is assumed in the synthesized waveform.

As an analytical tool for such a chemically patterned SAM surface, pulsed-force-mode atomic force microscopy (PFM-AFM) designed by Marti and coworkers [349] is useful as scanning force microscopy with chemical recognition capability [350, 351] (see chemical force... 

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