Optical field concentration in low-index waveguides

We present a highly efficient optical field concentrator that is capable of confining optical field in nanometer-thin low-index media with very high optical confinement factor. The structure is made of multiple-layered low-index nanolayers embedded in high-index silicon waveguides. By creating multiple high-index-contrast interfaces, the normal field in the low-index nanolayer regions is significantly enhanced. It subsequently results in a very high optical confinement and power density in these regions. With the help of numerical simulation tools, the guiding and propagating characteristics of the new structure are studied and presented. The optimal structures have demonstrated confinement factors and normalized power densities in the range of 30%-60% and 20-160 /spl mu/m/sup -2/ for the 5-20-nm thin low-index multiple nanolayers.     

Progress in reliability research in the micro and nano region

Due to the rapid development of IC technology the traditional packaging concepts are making a transition into more complex system integration techniques in order to enable the constantly increasing demand for more functionality, performance and miniaturisation. These new concepts will have to combine smaller structures and layers made of new materials with even higher reliability. As these structures will more and more display nano-features, a coupled experimental and simulative approach has to account for this development to assure design for reliability in the future. A necessary “nano-reliability” approach as a scientific discipline has to encompass research on the properties and failure behaviour of materials and material interfaces under explicit consideration of their nano-structure and the effects hereby induced. It uses nano-analytical methods in simulation and experiment to consistently describe failure mechanisms on that length scale for more accurate and physically motivated lifetime prediction models for use on a larger (i.e. then the micro) scale. This paper deals with the thermo-mechanical reliability of microelectronic components and systems and methods to analyse and predict it. Various methods are presented to enable lifetime prediction on system, component and material level, the latter introducing the field of nano-reliability for nano-packaging in advanced electronics system integration.     

Two‐phase thermo‐mechanical and macrosegregation modelling of binary alloys solidification with emphasis on the secondary cooling stage of steel slab continuous casting processes

As an approach towards a better modelling of solidification problems, we introduce a thermo‐mechanical and macrosegregation model that considers a solidifying alloy as a binary mixture made of a liquid and a solid phase. Macroscopic conservation laws for mass, momentum and solute are obtained by spatial averaging of the respective microscopic conservation equations. Assuming local thermal equilibrium, a single equation for the conservation of the mixture energy is then written. A single equation can be obtained for the solute as well by invoking a proper microsegregation rule. The numerical implementation in a two‐dimensional finite element code is then detailed. Lastly, some examples of simulations of academic tests as well as industrial applications for continuous casting of steel slabs are discussed. They particularly enlighten the ability of the formulation to describe the formation of central macrosegregation during the secondary cooling of slab continuous casting processes. Copyright © 2006 John Wiley & Sons, Ltd.     

Methodology for the reliability evaluation of a passive system and its integration into a Probabilistic Safety Assessment

A methodology has been developed to evaluate the reliability of passive systems characterised by a moving fluid and whose operation is based on thermal–hydraulic (T-H) principles. The methodology includes:

• identification and quantification of the sources of uncertainties and determination of the important variables;

• propagation of the uncertainties through T-H models and assessment of T-H passive system unreliability;

• introduction of passive system unreliability in the accident sequence analysis.

Each step of the methodology is described and commented and a diagram of the methodology is presented. An example of passive system is presented with the aim to illustrate the possibilities of the methodology. This example is the Residual Passive heat Removal system on the Primary circuit (RP2), an innovating system supposed to be implemented on a 900 MWe Pressurized Water Reactor.     

3-D high frequency computation of transformer R, L parameters

High frequency electrical machine modeling based on lumped parameter equivalent circuit requires that eddy currents effects be taken into account for R and L coefficient derivation. Substituting hysteretic materials (complex permeability) to conductive materials makes it possible to accurately approximate proximity losses and shielding effect while considering realistic meshes for finite element methods computation. Three-dimensional magnetodynamic simulations of transformer test-cases using anisotropic complex permeability for magnetic core and windings have shown a good agreement with the standard model results.     

A note on finding all homogeneous set sandwiches

A module is a set of vertices H of a graph G=(V,E) such that each vertex of V?H is either adjacent to all vertices of H or to none of them. A homogeneous set is a nontrivial module. A graph G_s=(V,E_s) is a sandwich for a pair of graphs G_t=(V,E_t) and G=(V,E) if E_t⊆E_s⊆E. In a recent paper, Tang et al. [Inform. Process. Lett. 77 (2001) 17-22] described an O(Δn²) algorithm for testing the existence of a homogeneous set in sandwich graphs of G_t=(V,E_t) and G=(V,E) and then extended it to an enumerative algorithm computing all these possible homogeneous sets. In this paper, we invalidate this latter algorithm by proving there are possibly exponentially many such sets, even if we restrict our attention to strong modules. We then give a correct characterization of a homogeneous set of a sandwich graph.     

Data-parallel tomographic reconstruction: A comparison of filtered backprojection and direct Fourier reconstruction

We consider the parallelization of two standard 2D reconstruction algorithms, filtered backprojection and direct Fourier reconstruction, using the data-parallel programming style. The algorithms are implemented on a Connection Machine CM-5 with 16 processors and a peak performance of 2 Gflop/s.     

Perception of difficulties for the back related to asssembly work: general findings and impact of back health

The study objective was to describe the perceptions of airplane assemblers on job demand for the back and how back pain modulated these perceptions. One hundred and seventy-six workers answered two questionnaires concerning back pain and the perception of work related difficulties (work activities, work contexts, tools, work positions, efforts). Results show that positions and work contexts are perceived as greater sources of difficulty than efforts or dynamic activities. The duration of a given position is more important than its frequency. Back pain has a significant but complex impact on the perception of difficulty. Assemblers appear to integrate several factors when evaluating their difficulties as opposed to individual aspects, as it is often measured in ergonomic studies. The results have important implications for the measurement of ergonomic factors in the genesis of back pain and illustrates the potential for misclassification and biases in current epidemiologic studies.     

Memory Management for Real-Time Java: An Efficient Solution using Hardware Support*

This paper addresses the issue of improving the performance of memory management for real-time Java applications, building upon the real-time specification for Java (RTSJ) from the Real-Time Java Expert Group. In a first step, a collecting dynamic memory solution including both a real-time garbage collector and region-based memory management, is proposed. A thorough analysis of the parameters influencing the performance of write barriers in memory management, together with ways of improvement are then presented. Finally, the implementation of a memory management solution compliant with the RTSJ and integrating the proposed improvements is sketched.     

Treatment of Point Defects in Nanowire MOSFETs Using the Nonequilibrium Green’s Function Formalism

A program to numerically simulate point defects in nanowire metal-oxide-semiconductor field-effect transistors is described. The simulation scheme is based on the non-equilibrium Green’s function method self-consistently being obtained via the resolution of 3D Poisson’s equation. A tight-binding hamiltonian is used and the point defect is characterized by a macroscopic coulombic tail treated in the mode-space approach, plus a short range on-site perturbation potential energy, treated exactly. The effect on internal quantities and on the transistor characteristics is studied as a function of the strength and the location of the defect potential. Subthreshold current is found to vary in a factor 10 according to the position of the impurity.Also With Institut Universitaire De France (IUF).