Single-crystal thin-film transistors on nonrefractory materials such as glass can be realized if monocrystalline islands of sufficient sizes can be grown at a predetermined position. By artificially controlling the super-lateral growth phenomenon observed in excimer-laser crystallization, this could be achieved. In this letter, we present such a method in which the silicon filling of a very small indentation fabricated in the substrate will act as a seed for lateral growth of large grains. When the melt is deep in these indentations, lateral growth is preceded by a vertical growth phase during which grains become occluded, so that a high yield of monocrystalline islands is obtained.

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many particle images. The particle motion and thus the velocity field are averaged over the extent of the interrogation window. For a measurement of small-scale turbulence quantities, the velocity field must be resolved accordingly. For example, the dissipation rate ǫ = ν i,j (∂u i /∂x j ) 2 , where ν is the kinematic viscosity, involves the sum of squared derivatives of the components u i of the velocity field. It requires the resolution of the velocity field down to the Kolmogorov scale η, where the velocity field is smooth and where derivatives can be estimated from finite differences. Normally, the linear dimension L of the interrogation window is much larger than η, so that the magnitude of derivatives is underestimated. The obvious cure is to make the interrogation window as small as η, at the expense of a very limited view of the velocity field (Tanaka and Eaton 2010). On the other hand, when the size of the interrogation window is well within the inertial range, a now popular approach involves the assumption that the statistics of the resolved velocity field ū is universal, with a universal relation between the measured derivatives of the spatially averaged field ū and the true dissipation rate, ǫ LE (Sheng et al. 2000),For interrogation windows with inertialrange dimensions, finite velocity differences u scale as �(�u) 2 � ∝ ǫ 2/3 L 2/3 , so that ǫ LE becomes independent of the window size. This approach is attractive as it provides a means of estimating the dissipation rate from PIV measurements that still provide information about the large-scale structure of the velocity field.The commonly used value of the Smagorinsky constant is C Sm = 0.17 (Sheng et al. 2000;Lavoie et al. 2007), butAbstract The result of a particle image velocimetry (PIV) measurement is a velocity field averaged over interrogation windows. This severely affects the measurement of small-scale turbulence quantities when the interrogation window size is much larger than the smallest lengthscale in turbulence, the Kolmogorov length. In particular, a direct measurement of the dissipation rate demands the measurement of gradients of the velocity field, which are now underestimated because the small-scale motion is not resolved. A popular procedure is to relate the statistical properties of the measured, but underresolved gradients to those of the true ones, invoking a large-eddy argument (Sheng et al. in Chem Eng Sci 55(20):4423-4434, 2000). We argue that the used proportionality constant, the Smagorinsky constant, should depend on the window overlap, on the used elements of the strain tensor, and on the way in which derivatives are approximated. Using an analytic description, PIV measurements of velocity fields from a kinematic simulation and experiments in a synthetic jetdriven turbulent flow with zero mean velocity, we propose new values for this constant.

Interferometric particle imaging provides a simple way to measure the probability density function (PDF) of droplet sizes from out-focus images. The optical setup is straightforward, but the interpretation of the data is a problem when particle images overlap. We propose a new way to analyze the images. The emphasis is not on a precise identification of droplets, but on obtaining a good estimate of the PDF of droplet sizes in the case of overlapping particle images. The algorithm is tested using synthetic and experimental data. We next use these methods to measure the PDF of droplet sizes produced by spinning disk aerosol generators. The mean primary droplet diameter agrees with predictions from the literature, but we find a broad distribution of satellite droplet sizes.