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Fog computing architecture is used in various environments such as smart manufacturing, vehicular ad hoc networks. However, as an extension of cloud computing, inheriting security challenges of clo...

Elliptical cross-sectional projectiles have recently attracted attention because they fit the flattened shape of earth-penetrating weapons. This study aims to investigate a rigid elliptical cross-sectional projectile with different geometrical characteristics penetration into the semi-infinite concrete targets by implementing a theoretical method. The general geometric models of four types of elliptical cross-sectional projectiles are introduced; closed-form penetration equations are then derived based on the dynamic cavity-expansion theory. Furthermore, the present models are validated by comparing the predicted penetration depths with the predictions obtained using the semi-empirical formulae and test data; the maximum deviation from the test data is 15.8%. In addition, the deceleration, velocity, and displacement of the projectiles during the penetration process are obtained based on the present models, and the penetration performance of the four types of elliptical cross-sectional projectiles is discussed by comparing the penetration depths. The conical-nose elliptical cross-sectional projectile exhibits the best penetration performance than the other three types if the nose length is sufficiently large, and the ogive-nose elliptical cross-sectional projectile gradually exhibits its penetration performance advantage with the increase in the nose length.

In view of the difficulty of manufacturing titanium alloy tubes, a U–O forming process was proposed to manufacture tubes with TA15 titanium alloy. The effect of the U–O forming process on the microstructure evolution of typical regions of TA15 tubes was investigated using electron backscattered diffraction technique. Results showed that the grain size of the U-shaped part was uniform when deformed at 750°С. Through microstructure evaluation of the O-shaped part, there were only slight changes concerning grain size compared with the initial plate because of the deformation sequence. However, in general, no significant changes concerning the grain size of most regions were observed when comparing the O-shaped tube with the initial plate, which indicated that the U–O forming process did not cause obvious changes in the initial microstructure in terms of grain size.

In this paper, uniaxial tensile tests are firstly conducted to evaluate the flow stress of AZ61 magnesium alloy at different temperatures and strain rates. A commercial finite element code of DEFORM 3D is used to simulate the plastic deformation of AZ61 magnesium alloy tube during a y-shape hydroforming process at elevated temperatures. The effects of loading paths with different feeding speed ratios and initial tube positions on the contact area at the counter punch surface at the bulge stage are discussed. The effects of friction coefficient on the contact area at the counter punch surface are also investigated. Finally, using a testing machine with a capacity of 40 tons of axial feeding, 30 MPa of internal pressure and 300oC of maximum temperature, y-shape hydraulic forming experiments of AZ61 magnesium alloy tubes at elevated temperatures are carried out. The analytical flow line patterns and thickness distribution of the formed product are compared with the experimental results.

Introduction of a time-accurate stabilized finite-element approximation for the numerical investigation of weakly nonlinear and weakly dispersive water waves is presented in this paper. To make the time approximation match the order of accuracy of the spatial representation of the linear triangular elements by the Galerkin finite-element method, the fourth-order time integration of implicit multistage Pade method is used for the development of the numerical scheme. The streamline-upwind Petrov–Galerkin (SUPG) method with crosswind diffusion is employed to stabilize the scheme and suppress the spurious oscillations, usually common in the numerical computation of convection-dominated flow problems. The performance of numerical stabilization and accuracy is addressed. Treatments of various boundary conditions, including the open boundary conditions, the perfect reflecting boundary conditions along boundaries with irregular geometry, are also described. Numerical results showing the comparisons with analytical solutions, experimental measurements, and other published numerical results are presented and discussed. Copyright © 2007 John Wiley & Sons, Ltd.

Process yield is the most common criterion used in the manufacturing industry for measuring process performance. A measurement index, called Spk, has been proposed to calculate the yield for normal processes. The measurement index pk establishes the relationship between the manufacturing specifications and the actual process performance, which provides an exact measure on process yield. Unfortunately, the sampling distribution of the estimated pk is mathematically intractable. Therefore, process performance testing cannot be performed. In this paper; we consider a normal approximation to the distribution of the estimated pk, and investigate its accuracy computationally. We compare the critical values calculated from the approximate distribution with those obtained using the standard simulation technique, for various commonly used quality requirements. Extensive computational results are provided and analyzed. The investigation is useful to the practitioners for making decisions in testing process performance based on the yield.

The variability of mtDNA hypervariable segment I (HVS I) sequences was investigated in a total of 48 birds belonging to 12 Chinese native chicken breeds. Sixteen haplotypes were identified from 35 polymorphic nucleotide sites which accounted for 6.4% of a sequenced 544 bp fragment. Diversity analysis of the haplotypes showed that Tibetan, Langshan and Henan cockfight chicken had only one haplotype, while ancient haplotypes existed in Taihe silky and Chahua chicken. Phylogenetic analysis of the haplotypes suggested that Chinese native chicken breeds shared 5 maternal lineages and some breeds would share the same maternal lineage, regardless of their external features and ecological types. Both divergent and phylogenetic analysis of the haplotypes indicated the close genetic relationships between the Chinese native chicken breeds and G. g. gallus and G. g. spadiceus from different areas, which implied that G. g. gallus and G. g. spadiceus were the original ancestors of the Chinese native chicken breeds. (Asian-Aust. J. Anim. Sci. 2004. Vol 17, No. 7 : 903-909)