Shadow image technique

Since we deal with a periodic pattern, it is possible to apply a technique that was originally invented by the French physicist and mathematician Jean Baptiste Joseph Fourier (1768-1830). Fourier was the first who showed that every periodic process (or an object like in our case) can be described as the sum (a superposition) of an infinite number of individual periodic events (e.g. waves). This process is known as Fourier synthesis. The inverse process, the decomposition of the periodic event or object yields the individual components and is called Fourier analysis. How Fourier synthesis works in practice is shown in Figure 4. To keep the example most simple, we will first consider only the projection (a shadow image) of the black squares onto the horizontal a-axis in the beginning (Figure 3). 

Particle size measurements were made using an UV-laser, shadow photographic technique. The particle sizing system displayed real-time droplet images onto a television monitor. The images (shadows) were obtained when a pulsed (30 times per second) UV-laser beam was directed through a spray scene onto a synchronized UV-sensitive vidicon camera/recorder. The narrow depth of field used by this system can record shadows from 300 in-focus droplets per second with a resolution down to approximately 0.3 /un in diameter. 

The shadow mask proximity printing technique projects the shadow image of the transmission mask onto a resist-coated wafer by scanning a 1-mm-diameter... 

Papadopoulos, G. (2000). Infaring tanperature by means of a novel shadow image velocimetry technique, J. Thermophys. Heat Transfer, 14(4), 593-600. 

Figure 3.1 Methods of patterning the surface for in situ STM studies, (a) Schematics of shadow technique. (Reprinted with permission from Ref. [12]. Copyright 2002, Wiley, Inc.) (b) STM image ofthe surface created by shadow technique. The shadow area uncovered by metal clusters is distinguished from the area covered with metal clusters by the...

Dark field Visualization technique for ashes produced by microincineration and fluorescence microscopy useful for low-contrast subjects Electron systems imaging EM shadowing Detection, localization, and quantitation of light elements Structural information from ordered arrays of macromolecules... 

Recently, Razumovskid441 studied the shape of drops, and satellite droplets formed by forced capillary breakup of a liquid jet. On the basis of an instability analysis, Teng et al.[442] derived a simple equation for the prediction of droplet size from the breakup of cylindrical liquid jets at low-velocities. The equation correlates droplet size to a modified Ohnesorge number, and is applicable to both liquid-in-liquid, and liquid-in-gas jets of Newtonian or non-Newtonian fluids. Yamane et al.[439] measured Sauter mean diameter, and air-entrainment characteristics of non-evaporating unsteady dense sprays by means of an image analysis technique which uses an instantaneous shadow picture of the spray and amount of injected fuel. Influences of injection pressure and ambient gas density on the Sauter mean diameter and air entrainment were investigated parametrically. An empirical equation for the Sauter mean diameter was proposed based on a dimensionless analysis of the experimental results. It was indicated that the Sauter mean diameter decreases with an increase in injection pressure and a decrease in ambient gas density. It was also shown that the air-entrainment characteristics can be predicted from the quasi-steady jet theory. 

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