Defect-related currents

In order to reduce the occurrence of rail-defect-related failures, various methods are used to detect rail defects. These methods include visual inspection by the track maintenance staff, ultrasonic defect detection, eddy-current testing, ground-penetrating radar, impedance spectroscopy, and electromagnetic acoustic transducers [16,17]. 

SWCNTs exhibit exceptional properties which are directly related to their defect-free graphitic structure. The current list of possible applications includes ... 

PMs. Likewise, the PRNP-M129M variant was present in 100% of PMs and UMs (42) (see Table 10.5). These association studies clearly show that in PMs and UMs there is an accumulation of AD-related polymorphic variants of risk that might be responsible for the defective therapeutic responses currently seen in these AD clusters (42). 

In 1937, dost presented in his book on diffusion and chemical reactions in solids [W. lost (1937)] the first overview and quantitative discussion of solid state reaction kinetics based on the Frenkel-Wagner-Sehottky point defect thermodynamics and linear transport theory. Although metallic systems were included in the discussion, the main body of this monograph was concerned with ionic crystals. There was good reason for this preferential elaboration on kinetic concepts with ionic crystals. Firstly, one can exert, forces on the structure elements of ionic crystals by the application of an electrical field. Secondly, a current of 1 mA over a duration of 1 s (= 1 mC, easy to measure, at that time) corresponds to only 1(K8 moles of transported matter in the form of ions. Seen in retrospect, it is amazing how fast the understanding of diffusion and of chemical reactions in the solid state took place after the fundamental and appropriate concepts were established at about 1930, especially in metallurgy, ceramics, and related areas. 

Eddy-Current Methods This is one of the earliest NDT methods and is still used Basically, this method reveals any differences tn electrical impedance between parts to be tested and a reference sample. Parts to be examined are passed through a coil or explored with a probe, and a trace appears on a CRT, Since magnetic and electrical characteristics are closely related to metallurgical quantities, a trace position or pattern or a meter reading clearly shows variations in metal hardness and composition, as well as defects. Both ferrous and nonferrous parts can be tested, and various coils, probes, and detector lips are available,... 

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