A new structure of cross-coupling controller for precise tracking in motion control is proposed in this paper. When compared with the conventional cross-coupling system, this new structure has the advantage that the compensators in CCC have a simpler design process than conventional ones and so does its stability analysis. The proposed compensator (or controller) is evaluated and compared experimentally with a traditional uncoupled controller on a microcomputer controlled dual-axis positioning system. The experimental results show that the new structure of cross-coupling controller remarkably reduces contour error. In addition, this new controller can be implemented easily on a majority of motion systems in use today via reprogramming the reference position command subroutine. 

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This study investigates the effect of Na content on the structural, optical, and electrical properties of sol-gel Na-doped ZnO films using x-ray diffraction, photoluminescence, and conductivity measurements. It is shown that a p-type conversion of the Na-doped ZnO film might be due to a combined effect of the increased substitutional-Na density and the decreased oxygen-vacancy (VO) density. However, excess Na incorporation into ZnO shows an ambiguous carrier type due to the increase in the donorlike VO density. These results indicate that compensation effects limit the hole concentration in the Na-doped ZnO films. In addition, when more Na is substituted into the ZnO system, the difference in the ionic radii of Zn2+ and Na+ starts playing an increasingly important role, causing the presence of tensile stress in the Na-doped ZnO film.

The rotational states of an adsorbed dipole molecule in an external electric field were investigated. The surface hindering potential was modeled as a finite conical well and a dipole-field interaction was added to the hindering potential. The molecular wave functions were expressed in terms of the eigenfunctions of molecular hindered rotation in the absence of electric field. Eigenenergies were determined by the matrix diagonalization procedures. Our results showed that, for both vertically and horizontally adsorbed molecules, there is avoided crossing between two adjacent rotational energy levels, as the field strength is increased, and finally all state energies decrease rapidly as the field strength is strong enough. The avoided crossing is due to the redistribution of wave function between different potential well regions. By employing the sudden unhindrance approximation, the rotational-state distributions of molecules desorbing from a solid surface in the presence of external electric field were calculated. Our results showed that the rotational-state distributions are significantly influenced by the external electric field. Since the electric field increases the ground-state energy of adsorbed molecule, the distribution shifts towards the high-J region if the electric field is applied to orient the molecular axis against the molecular preferred orientation. On the contrary, the distribution shifts towards the low-J region if the electric field is applied to orient the molecular axis towards molecular preferred orientation because the electric field decreases the ground-state energy of adsorbed molecule. The solutions to the finite conical well were also used to calculate the rotational alignment in the photodesorption of CO from Cr 2 O 3 (0001). Our results showed that at low-J values the CO molecules desorb like a helicopter, while at high-J values a cartwheel-like motion is preferred. This result is in qualitative agreement with the experimental observation.

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