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This paper starts from the premise that ground resistance is independent of earth-fault current and presents a new method for calculating the ground resistance of grounding grids using the finite-element method. The results obtained using the method proposed are compared with results measured experimentally and results published by other authors. Once ground resistance and earth-fault current are known, grid potential and touch-and-step voltages can be calculated. The main advantage of the method proposed here is that it permits us to analyze symmetrical and nonsymmetrical grids of any shape in uniform soils. It provides a fast-resolution industrial application with acceptable results for calculating the ground resistance of grounding grids of any shape. The results obtained with the proposed method are used as the basis for formulating an easy-to-use equation for calculating the ground resistance of grounding grids in uniform soils. Index Terms--Earth potentials, grounding grids, ground resistance, modeling, simulation, step voltage.

Strontium barium niobate (SBN) optical thin films using a pulsed lased deposition (PLD) method are prepared and both linear and nonlinear optical properties of SBN and Eu(super 3+) doped SBN films were investigated. Eu(super 3+) ions may substitute for Nb ions in SBN.

VO2 thin films deposited on fused-quartz substrates were prepared by a pulsed laser deposition technique. Vanadium dioxide shows an ultrafast, passive phase transition (PT) from a monoclinic semiconductor phase to a metallic tetragonal rutile structure when the sample temperature is above 68°C. The fast PT can also be optically induced by laser excitation. In this paper, we report the optical properties of prepared thin films by absorption and photoluminescence (PL) measurements. In addition, a degenerate-four-wave-mixing measurement was also conducted using a 30 ps YAG pulsed laser operated at 532 nm. It is the first time, to our knowledge, that a large polarizability and relatively slow nanosecond excited state dynamical processes have been identified in VO2. The polarizability is found to be ∼300 times greater than the χ(3) value of a CS2 reference. The mechanism for slow process is believed to be associated with the structural change. [Copyright &y& Elsevier]

Optical quality SrxBa1−xNb2O6 (SBN) thin films doped with Pr3+ ions were successfully grown on fused quartz substrates using a pulsed laser deposition technique. Both as-grown and annealed samples were studied at either room temperature or at 10 K. Luminescence measurements show that most 4f2→4f2 emissions from Pr3+ centers were efficiently quenched in the films. Strong red emission from 1D2 to 3H4 at ∼610 nm accompanied by weak emission to other 3Hj multiplets could be observed only by UV excitation into the SBN conduction band. At 10 K, the main emission peak splits into four components. In addition, a broadband SBN-host luminescence was identified at ∼560 nm in the annealed sample, associated with the charge-transfer vibronic exciton. As an interstitial ion, Pr3+ may occupy a 15-, 12-, 9- or 6-fold cage surrounded by oxygen and was found to occupy all four possible sites in SBN thin films. This behavior is different from Eu3+- SBN where Eu3+ only occupies a 6-fold site. [Copyright &y& Elsevier]