Buried pulse

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. 

In the case that Eq. 8.2 is applied to the moment tensor analysis, the discrepancy between the half-space solution and the infinite-space solution should be studied. Accordingly, Lamb s solutions for a buried pulse are compared with Green s functions in an infinite space. 

As stated in Chapter 7, a code for computing Lamb s solution due to a buried pulse was already published (Ohtsu Ono 1984). An infinite-space solution is presented in the literature (Aki Richards 1980). Thus a solution UNij in an infinite space due to a step-function force H(t) is obtained as,... 

Lasers, 9 729 14 654-706. See also Lasing atomic systems in, 14 666-669 basic mechanism of, 14 656—661 buried heterostructure, 14 701 carbon dioxide, 14 693-696 carbon monoxide application, 5 24 cavity optics and, 14 669-672 classes of, 14 666-667 cutting applications of, 14 695-696 dye, 14 702-705 effect of loss in, 14 670 excimer, 14 691-693 fast pulse production in, 14 673-678 fiber optics and, 11 129 in fine art examination/conservation, 11 412, 413... 

The measurement of fluorescence life-times has great value for probing structural features of proteins. It requires expensive equipment since very rapid extinction of the exciting nanosecond pulse is necessary and the rapid decay of the emission must then be measured. The decay of the tryptophan fluorescence of LADH is biphasic with x = 3.9 and 7.2 ns and these are assigned to buried Trp-314 and exposed Trp-15, respectively. ... 

EXAMPLE 2.4 Two leaky barrels of toxic material buried deep under a lake (unsteady, three-dimensional solution with two pulses and superposition)... 

Although C02 lasers offer limited line-tunability from 9 to 11 xm wavelength, the significant output power makes them amenable to some methods of explosives detection. C02 lasers also see application as light sources in some photoacoustic measurement schemes (Section 4.4.). For example, Chaudhary [20] has used a C02-based photoacoustic technique to detect ppb (by weight) amounts of TNT and RDX. McKnight et al. [21] has used the acoustic pulse from a focused C02 laser employing different spot sizes to identify buried objects. 

Eidmann K, Andiel U, Pisani F, Hakel P, Mancini RC, Junkel-Vives GC, Abdallah Jr. J, Witte K (2003) K-shell spectra from hot dense aluminum layers buried in carbon and heated by ultrashort laser pulses. J. Quant. Spectrosc. Ra. 81 133-146... 

The boxcar integrator is a device which is able to recover the waveform of a repetitive signal or measure the amplitude of a repetitive pulse buried in noise. The major advantage of using a boxcar integrator to measure lifetimes is the relatively low initial cost of the system. The boxcar is basically a sample-and-hold system with two modes of operation, single point and scan, which are used respectively for pulse measurement and waveform retrieval. The time of sampling is determined by a reference pulse that is... 

THE MORPHOLOGY AND OPTICAL PROPERTIES OF Fe, Cr AND Mg SILICIDE NANOCRYSTALLITES BURIED IN SILICON BY ION IMPLANTATION, PULSED TREATMENTS AND Si OVERGROWTH... 

Fig. 13. Structure of the bottom of Long Island Sound revealed by acoustic reflection profiles made with 7-kHz acoustic pulses. (Upper echo is produced by a 2(X)-kHz echo sounder.) (a) Section of end moraine capped by boulders and almost buried by marine mud. (b) Thick deposit of marine mud in central Long Island Sound on top of outwash sand with reflector above thought to be surface of lacustrine deposits, (c) Sand-to-mud transition zone in central Long Island Sound. In all records each division on the vertical scale is 600 mm.

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