Artificial neural network application of modeling failure rate for Boeing 737 tires

This paper presents an application of artificial neural network (ANN) technique for conducting the reliability analysis of Boeing 737 tires. For this purpose, an ANN model utilizing the feed‐forward back‐propagation algorithm as a learning rule is developed. The inputs to the neural network are the flight operational time and the number of landings as independent variables and the output is the failure rate of the tires. Two years of data are used for failure rate prediction model and validation. Model validation, which reflects the suitability of the model for future predictions, is performed by comparing the predictions of the model with that of Weibull regression model. The results show that the failure rate predicted by the ANN is closer in agreement with the actual data than the failure rate predicted by the Weibull model. The present work also identifies some of the common tire failures and presents representative results based on the established model for the most frequently occurring tire failure. Copyright © 2010 John Wiley & Sons, Ltd.     

Reduction of hygrothermal transverse stresses in unidirectional hybrid composites under cyclic environmental conditions

When fiber-reinforced polymer plates are exposed to cyclic environmental conditions, polymer matrix absorbs or desorbs continuously the moisture due to the variation in service temperature and relative humidity. Both temperature and moisture concentration produce an important hygrothermal transverse stresses, which are maximum on both edges of the composite plates. These transverse stresses which are more important at first times of moisture diffusion, can produce a probable damage of composite plates. To extend the durability of our composite plate, interplay hybrid composites are adopted to reduce the transverse stresses on edges. Therefore, a variation of the relationship between thicknesses of unidirectional hybrid composites constituents AS/3501-5 and T300/5208 is carried out in order to find minimal transverse stresses. This thicknesses variation enables us to find the best configuration which gives favourable service conditions of our hybrid composite, i.e., to predict firstly a considerable reduction of hygrothermal transverse stresses at both edges of our hybrid plate, secondly to reduce or to attenuate the edge effect developed in 6 days and 6 weeks periods.     

Thermal product estimation method for aerodynamics experiments

This paper presents an experimental technique to estimate the appropriate thermal product values of rugged and fast response temperature probes (TPs) for hypersonic aerodynamic experiments. Two types of scratches were used, mainly abrasive papers with different grit sizes and scalpel blades with different thicknesses, to form the probe junction. The effect of the scratch technique on the probe’s thermal product is investigated. The probes are tested and calibrated in the test section and in the end wall of shock tube facility. It is observed that the thermal product of a particular TP depends on the Mach number, junction scratch technique, and junction location, as well as on the enthalpy conditions. It is noted that, depending on the scratch technique, some of the TPs do not require individual calibration; however, calibration for others is likely to be needed.     

Approximation of the solution of inverse problem of scattering of electromagnetic waves on plane dielectrics

We propose a method for the determination of the material parameters of dielectric coatings according to the measured values of scattered electromagnetic fields which enables us to introduce an efficient procedure of processing of the data of measurements in the methods of nondestructive testing. As a specific feature of the proposed method for the solution of the formulated inverse problem, we can mention the possibility of reconstruction of piecewise continuous profiles of dielectric permittivity for laminated materials. The procedure of reconstruction is based on the method of integral equations. The solution of the problem is obtained approximately. The measured values of the coefficient of reflection of plane electromagnetic waves are extrapolated to the high-frequency region, which enables us to guarantee higher accuracy of reconstruction of the functions of dielectric permittivity for the analyzed structures.     

M?ssbauer and Electrical Studies of Mn x Co1?x Fe2O4 Compounds Prepared via Glycothermal Route

Manganese-cobalt ferrite powders (Mn _x Co_1?x Fe₂O₄ with x varying from 0.0 to?0.6) have been produced by glycothermal process from pure metal chlorides. Single phase cubic spinel structure and nanophase structure of the as-synthesized samples were confirmed by X-ray diffraction (XRD) and by transmission electron microscope (TEM). The results show that the produced powders have grain sizes in the range 7 to 13?nm. Fe-57 M?ssbauer spectra for as-synthesized and for annealed samples at 700???C (in Ar atmosphere for 1?hour) are found to be similar. No significant changes in the spectra are observed across the composition range studied. The variations of grain sizes, lattice parameters, and M?ssbauer parameters as a function of composition have also been investigated. Bulk samples in the form of pellets were also produced from the as-synthesized compounds for resistivity measurements. The temperature dependence of the electrical resistivity for the samples sintered at 1050???C were studied using the four-probe method, from room temperature to about 110???C in a PID controlled oven. Two possible mechanisms for resistivity involving T ^?1/2 and T ^?1 dependences are investigated.     

A systems engineering approach to validation of a pulmonary physiology simulator for clinical applications

Physiological simulators which are intended for use in clinical environments face harsh expectations from medical practitioners; they must cope with significant levels of uncertainty arising from non-measurable parameters, population heterogeneity and disease heterogeneity, and their validation must provide watertight proof of their applicability and reliability in the clinical arena. This paper describes a systems engineering framework for the validation of an in silico simulation model of pulmonary physiology. We combine explicit modelling of uncertainty/variability with advanced global optimization methods to demonstrate that the model predictions never deviate from physiologically plausible values for realistic levels of parametric uncertainty. The simulation model considered here has been designed to represent a dynamic in vivo cardiopulmonary state iterating through a mass-conserving set of equations based on established physiological principles and has been developed for a direct clinical application in an intensive-care environment. The approach to uncertainty modelling is adapted from the current best practice in the field of systems and control engineering, and a range of advanced optimization methods are employed to check the robustness of the model, including sequential quadratic programming, mesh-adaptive direct search and genetic algorithms. An overview of these methods and a comparison of their reliability and computational efficiency in comparison to statistical approaches such as Monte Carlo simulation are provided. The results of our study indicate that the simulator provides robust predictions of arterial gas pressures for all realistic ranges of model parameters, and also demonstrate the general applicability of the proposed approach to model validation for physiological simulation.     

Large-scale synthesis of hierarchical alpha-FeOOH flowers by ultrasonic-assisted hydrothermal route

In this paper, we report a facile, an environmental friendly ultrasonic-assisted hydrothermal route for preparation of goethite flower structures using Fe nanopowders at low temperature (85°C). The flower structure consisted of tens of hundreds of nanowires and such structures can further self-assemble with the flake with micro size area. Structural, morphological, and elemental analysis revealed that the products consisted of flower-like structures with high structural uniformity, good crystal quality, and high yields. Influencing factors such as the reaction temperature, pH value, and the deposition time were systematically investigated. A possible formation mechanism was proposed on the basis of the experimental results. Magnetic measurements showed that the as-obtained goethite flowers exhibited weakly ferromagnetic characteristics at room temperature, which were quite different from those of the corresponding bulk materials.     

Effect of Bi content on spalling behavior of Sn–Bi–Zn–Ag/Cu interface

The effect of the Bi content on the formation of intermetallic compounds (IMCs) layers between the Sn-xBi-0.9Zn-0.3Ag lead-free solder (with x = 1, 2, 3 and 4, in weight percent, hereafter) and Cu substrate was investigated. The structure of the IMC layer in the soldered interface varies apparently with increasing the Bi content. When the Bi content is 1 wt%, the interface soldered is consisted of CuZn and Cu₆Sn₅ IMC layers, which are separated by an intermediate solder layer. As the Bi content increases, the spalling phenomenon tends to disappear. Moreover, the layer between the Sn-2Bi-0.9Zn-0.3Ag solder and Cu substrate is thicker than others. The evolution of the soldered interfacial structure could be attributed to the existence of Bi.     

Scalable total BETI based solver for 3D multibody frictionless contact problems in mechanical engineering

A total BETI (TBETI) based domain decomposition algorithm with the preconditioning by a natural coarse grid of the rigid body motions is adapted for the solution of multibody frictionless contact problems of linear elastostatics and proved to be scalable, i.e., the cost of the solution is asymptotically proportional to the number of variables. The analysis admits floating bodies. The proofs combine the original results by Langer and Steinbach on the scalability of BETI for linear problems and our development of optimal quadratic programming algorithms for bound and equality constrained problems. The theoretical results are verified by numerical experiments. The power of the method is demonstrated on the analysis of ball bearings.