Barker code

The Barker code pulse compression technique is a special ultrasonic testing method that compresses the ultrasonic pulse through the use of a special class of binary code called the Barker code [49], The pulse compression techique can be used to overcome the limitations of the traditional pulse-echo techique and is useful in testing materials that cause high attenuation. 

The maximum length of a Barker code is 13, and this code has sidelobes of —22.3 dB. The phase will look like -E -E -E -E H---EH------1----E,or-----------E H------1----E -. 

Notice that this is an orthogonal design in coded factor space (-1 and +1) any one column multiplied by any other column will give a vector product of zero. Other saturated fractional factorial designs may be found in the literature [Box and Hunter (1961a, 1961b), Anderson and McLean (1974), Barker (1985), Bayne and Rubin (1986), Wheeler (1989), Diamond (1989)]. 

Molecule-Molecule and Molecule-Metal Potentials, There are continuing improvements in molecule-molecule potentials. High quality efforts are directed at improving the interaction, including electronic polarizability and other tensor prop-erties[21, 22]. There are also potentials that include three body terms explicitiy[23]. Possibly the best atom-metal potential is due to Barker[24]. The Barker potential for Xe/Pt(lll) is an excellent fit to a large body of experimental data. There have been numerous quantum chemistry studies of ions and water on metal clusters some with applied fields and others on charged clusters to imitate the electrochemical environment (for water references see Zhu[2S], for ions on clusters see Pacchioni[26]). So far only a few have been parameterized into forms that can be easily used in an MD code[25, 27-29]. Electric double layers on Ag and Au are thermodynamically stable over wide potential range[30]. It is unfortunate that simulations have focussed almost exclusively on Pt for which there is little experimental... 

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