Black-spot analysis

Accident-concentration analysis was first developed within traffic-safety research and was here denoted black-spot analysis . By analysing the geographical distribution of traffic accidents, instances of poor design of the road network could be identified. The accident black spots were the geographical locations (e.g. crossings), where many of the accidents occurred. The remedial actions were channelled to these locations. 

Figure 9.13 Microlocal analysis by LA-ICP-MS on a tested solid oxide fuel cell with local Impurities. The small black spots are the laser craters. (]. S. Becker, Spectrochim. Acta 57B, 1805 (2002). Reproduced by permission of Elsevier.)...

Another approach to explain foam film rupture has been developed by de Vries [101] who proposed to consider film rupture as a result of fluctuational formation of holes (black spots) in it - nuclei of critical size (see Section 3.4). This idea was used in the analysis of the... 

Theoretical analysis of sheeting in the drainage of thin liquid films has been conducted in [359]. Sheeting dynamics and hole formation (i.e. black spot formation) was described by non-linear hydrodynamic stability analysis based on the equilibrium oscillatory structural component of disjoining pressure. The effect of stepwise thinning, accompanied by formation of holes , was described qualitatively. It is rather arguable whether the term holes for a black spot is appropriate since in 1980 holes in NBF were described as lack of molecules. The use the same term for two different formations is at least confusing. Besides, to have a hole in a CBF is almost as to have a hole in the sea water . 

The results about spreading of antifoams as well as the inhibition of black spot formation in microscopic foam films, permit to draw a conclusion about the existence of a special mechanism of heterogeneous defoaming, based on the stability analysis [14,25,48]. The details of this mechanism are given later [18,55,56]. For the defoaming action of hydrophobic solid particles in heterogeneous system another (bridge) mechanism has been proposed [57]. Later it was applied on drops, mixtures of hydrocarbon oil and hydrophobic particles [19,20,53,54]. 

A common technique for organic compounds is spraying the plate with a sulfuric acid solution and then heating it to char the compounds and develop black spots. This precludes quantitative analysis by scraping the spots off the plate and eluting for measurement. 

In failure analysis the possibility to record all elements is advantageous, not least in combination with 3D imaging (i.e., a TOF-SIMS instrument with dual-beam capability is the instrument of choice). An example is the investigation of black spots in OLEDs where a fluorine-based polymer was sandwiched between a metallic cathode consisting of Ba and A1 and a poly(3,4-ethylenedioxythiophene)/ITO anode. From the recorded raw data, depth profiles can be reconstructed as well as two-dimensional (2D) images in any depth or a 3D representation of all interesting signals. It was found that aluminum was oxidized at the Al/polymer interface [220]. 

Larsson, TJ, Rechnitzer, G, Ozanne-Smith, J, Newstead, S Gantzer, S (1997a) Strategic Occupational Injury Prevention Occupational Black Spots - Victoria (Analysis and Priorities). Policy Report No 6, Part 1. Victorian Workcover Authority, Melbourne. 

An alternate hypothesis investigated in this analysis is differential heating. During extrusion of a sheet, some times black spots are seen on the surface (for our study, consider bottom surface). Black defects likely due to resin degradation... 

Further, we examined the Heck reaction between w-butyl acrylate and 4-bromobenzotrifluoride 5 in the presence of 2 mol% Pd clusters in a singlevessel monomode m/w oven fitted with an infrared thermometer. 100% conversion with quantitative yield to the cinnamate was obtained after 5 min irradiation at 75 W/240 °C. We then repeated the reaction under conventional heating at 240 °C. After 3.5 min a black tarry gel formed. Extraction followed by GC analysis showed only cinnamate, but the tarry material (probably acrylate polymers/oligomers) could not be analysed. These experiments show that when clusters are present different results are obtained depending whether m/w heating or conventional heating is used. In principle, this could be the result of hot spots created on the metal clusters. 

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