Eddy Current Thickness Measurement of the Zink Layer on Galvanized Steel Wires

By resolving Maxwell’s Equations for the case of a long coil encircling a galvanized wire (fig.l), we can calculate the normalized impedance diagram. Later, during the experiments, we will directly use this diagram to find the thickness of the zinc layer. Before resolving Maxwell’s Equations, a few words about the normalized impedance diagram in general. Figure 2 shows the normalized impedance diagram for the simple case of a long coil encircling a wire made out of a homogeneous conductive material of permeability µr and with a fill factor equal to one. A fill factor, η=a2/c2 (fig. 3), equal to one, means that there is no air between the coil and the wire. The x axis represents the normalized resistance (1) (Rp−Re)/ωLe, where Rp is the real component of the impedance Zp of the coil when there is a part inside the coil, Re and ωLe are respectively the real and the imaginary components of Ze when the coil is empty

Efficient Eddy Current Models for Evaluation of Thin Conductive Coatings on Ferromagnetic Substrates

Eddy current testing is widely used to determine physical characteristics of materials and to detect flaws by measurements of the electrical impedance of an eddy current probe. In this paper two analytical models allowing to determine properties of non-magnetic conductive coatings on ferromagnetic conductive substrates, are reported. Operating at a single frequency, two following quantities can be determined: permeability-to-conductivity ratio of the substrate and thickness-conductivity product of the coating [1, 2]. The method was validated using both long solenoids and air core surface coils, and was applied to the evaluation of zinc coatings on steel wires and sheets. The theoretical solutions given for high arguments are compact, and allow fast inversion, respectively around 400 and 10 ms for a pancake surface coil and for a long encircling solenoid. Two series of samples: Ø2.2 mm low carbon steel electro galvanized wires and 0.75–20 mm thick hot dip galvanized sheets, were inspected. Steel sheet samples with artificial coatings, as aluminum foils glued from both sides, were also examined. Experimental data of the coil electrical impedance were compared to those predicted. Agreement between theory and experiment is excellent. The technique developed has an extremely low sensitivity to the substrate conductivity and permeability variations [2]. A DC magnetic field, significantly diminishing the permeability of the substrate, almost does not influence results of the coating thickness determination. The agreement between measured thickness and that obtained by other methods is excellent. The accuracy of the thickness determination typically about 1 μ is obtained

Large electronic bandwidth in solution-processable pyrene crystals: The role of close-packed crystal structure

We examine the interdependence of structural and electronic properties of two substituted pyrene crystals by means of combined spectroscopic probes and density-functional theory calculations. One derivative features n-hexyl side groups, while the other one contains branched silanyl groups. Both derivatives form triclinic crystal structures when grown from solution, but the electronic dispersion behavior is significantly different due to differences in $\pi$-$\pi$ overlap along the $a$ crystal axis. Both systems display dispersion of 0.40-0.45 eV in the valence band, suggesting a high intrinsic hole mobility. However, the dispersion is primarily along the a-axis in the silanyl-substituted derivative, but less aligned with this crystal axis in the hexyl-substituted material. This is a direct consequence of the diferences in co-facial $\pi$ electron overlap revealed by the crystallographic studies. We find that photophysical defects, ascribed to excimer-like states, point to the importance of localized trap states. Substituted pyrenes are useful model systems to unravel the interplay of crystal structure and electronic properties in organic semiconductors.Comment: 25 pages, 8 figure

Feasibility of non-invasive pressure support ventilation in infants with respiratory failure after extubation: a pilot study

Objective: To evaluate the feasibility and effects of non-invasive pressure support ventilation (NIV) on the breathing pattern in infants developing respiratory failure after extubation. Design: Prospective pilot clinical study; each patient served as their own control. Setting: A nine-bed paediatric intensive care unit of a tertiary university hospital. Patients: Six patients (median age 5months, range 0.5-7months; median weight 4.2kg, range 3.8-5.1kg) who developed respiratory failure after extubation. Interventions: After a period of spontaneous breathing (SB), children who developed respiratory failure were treated with NIV. Measurements and results: Measurements included clinical dyspnoea score (DS), blood gases and oesophageal pressure recordings, which were analysed for respiratory rate (RR), oesophageal inspiratory pressure swing (dPes) and oesophageal pressure-time product (PTPes). All data were collected during both periods (SB and NIV). When comparing NIV with SB, DS was reduced by 44% (P<0.001), RR by 32% (P<0.001), dPes by 45% (P<0.01) and PTPes by 57% (P<0.001). A non-significant trend for decrease in PaCO2 was observed. Conclusion: In these infants, non-invasive pressure support ventilation with turbine flow generator induced a reduction of breathing frequency, dPes and PTPes, indicating reduced load of the inspiratory muscles. NIV can be used with some benefits in infants with respiratory failure after extubatio

Parameterized Unit Testing in the Open Source Wild

With recent advances in test generation research, powerful test generation tools are now at the fingertips of developers in software industry. For example, Microsoft Research Pex, a state-of-the-art tool based on dynamic symbolic execution, has been shipped as IntelliTest in Visual Studio 2015. For test inputs automatically generated by such tool, to supply test oracles (beyond just uncaught runtime exceptions or crashes), developers can write formal specifications such as code contracts in the form of preconditions, postconditions, and class invariants. However, just like writing other types of formal specifications, writing code contracts, especially postconditions, is challenging. In the past decade, parameterized unit testing has emerged as a promising alternative to specify program behaviors under test in the form of unit tests. Developers can write parameterized unit tests (PUTs), unit-test methods with parameters, in contrast to conventional unit tests, without parameters. PUTs have been popularly supported by various unit testing frameworks for .NET along with the recent JUnit framework. However, there exists no study to offer insights on how PUTs are written by developers in either proprietary or open source development practices, posing barriers for various stakeholders to bring PUTs to widely adopted practices in software industry. To fill this gap, in this paper, we present the first empirical study of parameterized unit testing conducted on open source projects. We study hundreds of parameterized unit tests that open source developers wrote for these open source projects. Our study findings provide valuable insights for various stakeholders such as current or prospective PUT writers (e.g., developers), PUT framework designers, test-generation tool vendors, testing researchers, and testing educators.Ope

A Characteristic Study of Parameterized Unit Tests in .NET Open Source Projects

In the past decade, parameterized unit testing has emerged as a promising method to specify program behaviors under test in the form of unit tests. Developers can write parameterized unit tests (PUTs), unit-test methods with parameters, in contrast to conventional unit tests, without parameters. The use of PUTs can enable powerful test generation tools such as Pex to have strong test oracles to check against, beyond just uncaught runtime exceptions. In addition, PUTs have been popularly supported by various unit testing frameworks for .NET and the JUnit framework for Java. However, there exists no study to offer insights on how PUTs are written by developers in either proprietary or open source development practices, posing barriers for various stakeholders to bring PUTs to widely adopted practices in software industry. To fill this gap, we first present categorization results of the Microsoft MSDN Pex Forum posts (contributed primarily by industrial practitioners) related to PUTs. We then use the categorization results to guide the design of the first characteristic study of PUTs in .NET open source projects. We study hundreds of PUTs that open source developers wrote for these open source projects. Our study findings provide valuable insights for various stakeholders such as current or prospective PUT writers (e.g., developers), PUT framework designers, test-generation tool vendors, testing researchers, and testing educators