Penetration length/depth

London penetration depth, At, is the penetration length of the twist distortion, and the equivalent of the coherence length, co, is the correlation length of the smectic phase. In a screw dislocation, the core of the defect approximates to the smectic correlation length and a twist of 90° to the penetration depth, see Fig. 14(b). 

The sidewall sampling tool (Sl/VS) can be used to obtain small plugs (2 cm diameter, 5 cm length, often less) directly from the borehole wall. The tool is run on wireline after the hole has been drilled. Some 20 to 30 individual bullets are fired from each gun (Fig. 5.35) at different depths. The hollow bullet will penetrate the formation and a rock sample will be trapped inside the steel cylinder. By pulling the tool upwards, wires connected to the gun pull the bullet and sample from the borehole wall. 

In this case the probe diameter and the slot length are of similar size. The material chosen has penetration depth of 0.7 ram at the given frequency of 16.9 kHz. The slot depth is 7 times larger than the penetration depth. 

The case considered above corresponds to R < H. The calculation using formula (1) gives the next results. For example, consider the thickness of dry developer layer h = 20 pm. In the absence of sedimentation process our product family (penetrant and developer indicated above) could not detect the cracks with the depth lo < 1,33 mm of any widths. Nevertheless due to the sedimentation one can get the decrease of developer s thickness from h = 20 pm till h s 5 pm. As a result, our product family can ensure the detection of the cracks with H > 2,3 pm even with very small length lo = 0,4 mm. At the same time if lo = 1 mm, then the cracks with extremely small width H > 0,25 will be revealed. 

Knoop developed an accepted method of measuring abrasive hardness using a diamond indenter of pyramidal shape and forcing it into the material to be evaluated with a fixed, often 100-g, load. The depth of penetration is then determined from the length and width of the indentation produced. Unlike WoodeU s method, Knoop values are static and primarily measure resistance to plastic flow and surface deformation. Variables such as load, temperature, and environment, which affect determination of hardness by the Knoop procedure, have been examined in detail (9). 

Production through much of the year will be subject to other constraints for example, the availability of light beneath the water surface. Seasonal differences in day length and periodic fluctuations in the depth of light penetration by active wavelengths often have an overriding effect on the net production rates and the supportive capacity. 

On about 25(X) km of pipeline laid since 1970, overline surveys showed 84 places totalling 5 km in length where the protection criterion had not been reached. In 21 exploratory excavations, 7 cases of pitting corrosion with penetration depths > 1 mm were found. At three places the pipe had to be replaced or repaired with split sleeves. Seven hundred sixty-five places with a total length of 95 km in 25(X) km of pipeline laid between 1928 and 1970 were found to have failed to reach the protection criterion. Thirty-two examples of pitting corrosion with > 1 mm were... 

Many inorganic solids lend themselves to study by PL, to probe their intrinsic properties and to look at impurities and defects. Such materials include alkali-halides, semiconductors, crystalline ceramics, and glasses. In opaque materials PL is particularly surface sensitive, being restricted by the optical penetration depth and carrier diffusion length to a region of 0.05 to several pm beneath the surface. 

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