Steers

It is in fact the tick-off heuristic that steered the design toward the minimum number of units. The target for the minimum number of units was given by Eq. (7.2) ... 

If a shallow kick off in soft formation is required (e.g. to steer the borehole away underneath platforms) a technique using jet bit deflection or badgering is employed (Fig. 3.16). A rock bit is fitted with two small and one large jet. With the bit on bottom and oriented in the desired direction the string is kept stationary and mud is pumped through the nozzles. This causes asymmetric erosion of the borehole beneath the larger jet. Once sufficient hole has been jetted, the drill bit will be rotated again and the new course followed. This process will be repeated until the planned deviation is reached. 

The Scania plant at Falun in Sweden manufaetures bus and truck steering knuckles. These are safety-critical components that are specified as having to be crack-free. For this reason, every component is now inspected using an automatic process that ensures the appropiate inspection is consistently canied out to the required standards of quality. Photos of the system are shown in Fig 1. The principle of operation is as follows. 

The experimental investigations are carried out in order to get an idea about the variations of the visibility of the indications during practical inspections. The specimen where a test piece with spare eroded artificial defects (Width 25 pm depth d = 30, 60, 120 pm) and other specimen with natural cracks, a forged steering lever and a weld. As an example, in Fig 4 the steering lever with 2 cracks can be seen and below the dependance on the visibilty of a weak indication and a part of the bright indications on the field strenght H. 

Fig. 5 Indications of natural defects in a forged steering lever...

This paper intends to give, through different examples, guide-lines for characterization of array probes. We discuss, particularly, beam pattern measurement methods and raise the question whether it is useful to achieve a full characterization of all beams steered by the probe or to limit the characterization to a minimum set of acoustic configurations. An automatic bench for full characterization of tube inspection probes is described. 

We recall that, for flat array, the steered angle beam, 9, depends only on ultrasound celerity in the propagation medium, ci, the time delay between each element, 5t, and the pitch element, p, through the relation ... 

Similarly, the focusing capability of an array is the strongest focused beam which can be steered. The simplest way to evaluate it is to test a theoretical focusing time delay law, in the near-field and in the natural direction of propagation of the array. The beam pattern characteristics depth, lateral size and length of the focal spot must be found consistent with modelling and no lobe must appear above a predetermined level. 

The required acoustic verifications depend on what the probe is made for. If the probe is used as an angular scamiing system with a fix set of elements, then we think it is only needed to characterize the array behavior with a few selected time delay laws to isolate the angular steering capability and the foeusing capability as explained before. 

It turns out that there is another branch of mathematics, closely related to tire calculus of variations, although historically the two fields grew up somewhat separately, known as optimal control theory (OCT). Although the boundary between these two fields is somewhat blurred, in practice one may view optimal control theory as the application of the calculus of variations to problems with differential equation constraints. OCT is used in chemical, electrical, and aeronautical engineering where the differential equation constraints may be chemical kinetic equations, electrical circuit equations, the Navier-Stokes equations for air flow, or Newton s equations. In our case, the differential equation constraint is the TDSE in the presence of the control, which is the electric field interacting with the dipole (pemianent or transition dipole moment) of the molecule [53, 54, 55 and 56]. From the point of view of control theory, this application presents many new features relative to conventional applications perhaps most interesting mathematically is the admission of a complex state variable and a complex control conceptually, the application of control teclmiques to steer the microscopic equations of motion is both a novel and potentially very important new direction. 

Figure Al.6.26. Stereoscopic view of ground- and excited-state potential energy surfaces for a model collinear ABC system with the masses of HHD. The ground-state surface has a minimum, corresponding to the stable ABC molecule. This minimum is separated by saddle points from two distmct exit chaimels, one leading to AB + C the other to A + BC. The object is to use optical excitation and stimulated emission between the two surfaces to steer the wavepacket selectively out of one of the exit chaimels (reprinted from [54]).

The object now will be to steer the wavefunction out of a specific exit chaimel on the ground electronic state, using the excited electronic state as an intennediate. Insofar as the control is achieved by transferring amplitude between two electronic states, all tire concepts regarding the central quantity introduced above will now come into play. 

Figure A3.9.11. Dissociation of H2 on the W(100)-c(2 x 2)-Cu surface as a function of incident energy [71]. The steering dominated reaction [102] is evident at low energy, confmned by the absence of a significant surface temperature.

Gi-op A, Wilke S and Scheffler M 1995 6-dimensional quantum dynamics of adsorption and desorption of H2 at Pd(IOO)-steering and steric effects Phys.Rev. Lett. 75 2718... 

Kay M, Darling G R, Holloway S, White J A and Bird D M 1995 Steering effects in non-activated adsorption Chem. Phys. Lett 245 311... 

Chaimelling phenomena were studied before Rutherford backscattering was developed as a routine analytical tool. Chaimelling phenomena are also important in ion implantation, where the incident ions can be steered along the lattice planes and rows. Channelling leads to a deep penetration of the incident ions to deptlis below that found in the nonnal, near Gaussian, depth distributions characterized by non-chaimelled energetic ions. Even today, implanted chaimelled... 

Kozack R E, d Mello M J and Subramaniam S 1995 Computer modeling of electrostatic steering and orientational effects in antibody-antigen association Biophys. J. 68 807-14... 

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