Investigation on Ballistic Performance of Armor Ceramics against Long-Rod Penetration

A series of depth-of-penetration (DOF) tests are carried out to investigate the ballistic performance of armor ceramics. Based on the experimental results, an improved differential efficiency factor (DEF) is presented, which demonstrates that the general ballistic efficiency index is independent of the ceramic thickness. It is also shown that the density, internal friction, and compression strength of ceramics are crucial factors that affect the ballistic performance of ceramics significantly through the interaction between the long-rod projectiles and thick-tile armor. This article is based on a presentation made in the symposium entitled “Dynamic Behavior of Materials,” which occurred during the TMS Annual Meeting and Exhibition, February 25–March 1, 2007 in Orlando, Florida, under the auspices of The Minerals, Metals and Materials Society, TMS Structural Materials Division, and TMS/ASM Mechanical Behavior of Materials Committee.     

Representation and uniformization of algebraic transductions

This paper explores different means of representation for algebraic transductions, i.e., word relations realized by pushdown transducers. The relevance of this work lies more in its point of view rather than any particular result. We are aiming at giving specific techniques for obtaining, or perhaps explaining, decompositions of algebraic (and incidentally, rational) relations, relying solely on their “machine” definition rather than some complex algebraic apparatus. From this point of view, we are hoping to have demystified the heavy formalism employed in the present literature. Some of the novelties of our work are: the use of “stack languages” and “embeddings,” which eliminate the need of arbitrary context-free languages in our characterizations, the study of uniformizations for algebraic transductions and the use of the so-called stack transductions for exposing the anatomy of pushdown transducers.This work was supported by the Natural Science and Engineering Research Council of Canada grants R220259 and OGP0041630.     

Correlation relations for estimating the content of plutonium isotopes in fallout due to the Chernobyl accident

The possibility of determining the total α activity A(^239,240Pu) of ²³⁹Pu + ²⁴⁰Pu according to the γ radiation of ¹⁰³Ru and ¹⁰⁶Ru is examined. The statistical properties of the experimental ratios of the activities ρ = A(¹⁰⁶Ru)/A(¹⁰³Ru) are investigated. The distribution of the experimental ratios is similar to the theoretical ratios for fuel and close to a Gaussian distribution with average value 〈p〉 = 0.22 and standard deviation Δ ∼ 0.06. This ratio is used to obtain a relation for estimating A(^239,240Pu) from the γ activity A(¹⁰³Ru). A theoretical analysis is made of the experimental data for the southern raions of Gomel oblast. It is shown that given a good statistical sample of measurements of the γ activity of ¹⁰³Ru it is possible to estimate the average value of the γ activity A(^239,240Pu) and with probability 0.95 the interval of the possible values of this activity. __________ Translated from Atomnaya énergiya, Vol. 103, No. 4, pp. 255–259, October, 2007.     

Modellgetriebene,mustergestützte Sicherheit in serviceorientierten Architekturen

Ohne Zusammenfassung     

Distributed Context Retrieval and Consistency Control in Pervasive Computing

The challenge of saturating all phases of pervasive service provision with context-aware functionality lies in coping with the complexity of maintaining, retrieving and distributing context information. To efficiently represent and query context information a sophisticated modelling scheme should exist. To distribute and synchronise context knowledge in various context repositories across a multitude of administrative domains, streamlined mechanisms are needed. This paper elaborates on an innovative context management framework that has been designed to cope with free-text and location based context retrieval and efficient context consistency control. The proposed framework has been incorporated in a multi-functional pervasive services platform, while most of the mechanisms it employs have been empirically evaluated.     

A Study of Surface Deformation during Wire‐Rod Rolling of High Speed Steels using Experimental and Computational Techniques

The evolution of surface defects during shape rolling of high‐speed steel billets is studied using longitudinal surface defects prepared by machining and welding. The reduction of the defects during rolling in a production mill is compared to the total area reduction of the billets. Samples are collected after pass 4, 6, 8, 14, 19 and the final pass, 28, representing the finished 5.5mm wire. By inspecting the cross sections, the rotation of the billets from pass to pass is evaluated. Results from FE simulations on solid billets are compared to the experimental results. Generally, simulations predict less reduction than observed experimentally. In most cases cracks reduce most effectively followed by carbon steel welds and stainless steel welds.     

On the stability of colocated clustered finite volume simplicial discretizations for the 2D Stokes problem

Abstract  In this paper, we give a new (and simpler) stability proof for a cell-centered colocated finite volume scheme for the 2D Stokes problem, which may be seen as a particular case of a wider class of methods analyzed in [10]. The definition of this scheme involves two grids. The coarsest is a triangulation of the computational domain by acute-angled simplices, called clusters. The control volumes grid is finer, built by cutting each cluster along the lines joining the mid-edge points to obtain four sub-triangles. By building a Fortin projection operator explicitly, we prove that the pair of discrete spaces associating the classical cell-centered approximation for the velocities and cluster-wide constant pressures is inf-sup stable. In a second step, we prove that a stabilization which involves pressure jumps only across the internal edges of the clusters yields a stable scheme with the usual colocated discretization (i.e., with the cell-centered approximation for the velocity and the pressure). Lastly we give an interpretation of this stabilization as a “minimal stabilization procedure”, as introduced by Brezzi and Fortin. Keywords: Incompressible Stokes equations, Finite volumes, Stability     

Maximization of mutual information for supervised linear feature extraction.

In this paper, we present a novel scheme for linear feature extraction in classification. The method is based on the maximization of the mutual information (MI) between the features extracted and the classes. The sum of the MI corresponding to each of the features is taken as an heuristic that approximates the MI of the whole output vector. Then, a component-by-component gradient-ascent method is proposed for the maximization of the MI, similar to the gradient-based entropy optimization used in independent component analysis (ICA). The simulation results show that not only is the method competitive when compared to existing supervised feature extraction methods in all cases studied, but it also remarkably outperform them when the data are characterized by strongly nonlinear boundaries between classes.