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Global Parameters (global + parameter)

Distribution by Scientific Domains

Engineering	50%

Selected Abstracts

Fabrication of a Memory Chip by a Complete Self-Assembly Process Using State-of-the-Art Multilevel Cell (MLC) Technology,

ADVANCED FUNCTIONAL MATERIALS, Issue 8 2008
Anirban Bandyopadhyay
Abstract Using a two bit molecular switch, an ultra-dense memory chip has been built following a fully automated fabrication process. Well-ordered templates are grown naturally using a well-defined protocol of temperature variation. This template is so designed that molecules are adsorbed selectively only into particular sites whenever they are bombarded on the template through an e-beam evaporator for a particular time. The technique is a generalized protocol that has been used to grow atomic-scale templates by proper tuning of basic global parameters like temperature and evaporation time. Tuning of the basic template parameters is also demonstrated here, and has been used to scale down parameter values following the same route. Tuning the junction profile should allow selective adsorption of more complicated multi-level switches in future. Therefore, a fairly simple technology has been established that addresses one of the most fundamental issues of continuous miniaturization, i.e., simultaneous automated growth of thousands of atomically precise single molecular devices. [source]

Two-dimensional prediction of time dependent, turbulent flow around a square cylinder confined in a channel

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 11 2010
M. Raisee
Abstract This paper presents two-dimensional and unsteady RANS computations of time dependent, periodic, turbulent flow around a square block. Two turbulence models are used: the Launder,Sharma low-Reynolds number k,, model and a non-linear extension sensitive to the anisotropy of turbulence. The Reynolds number based on the free stream velocity and obstacle side is Re=2.2×104. The present numerical results have been obtained using a finite volume code that solves the governing equations in a vertical plane, located at the lateral mid-point of the channel. The pressure field is obtained with the SIMPLE algorithm. A bounded version of the third-order QUICK scheme is used for the convective terms. Comparisons of the numerical results with the experimental data indicate that a preliminary steady solution of the governing equations using the linear k,, does not lead to correct flow field predictions in the wake region downstream of the square cylinder. Consequently, the time derivatives of dependent variables are included in the transport equations and are discretized using the second-order Crank,Nicolson scheme. The unsteady computations using the linear and non-linear k,, models significantly improve the velocity field predictions. However, the linear k,, shows a number of predictive deficiencies, even in unsteady flow computations, especially in the prediction of the turbulence field. The introduction of a non-linear k,, model brings the two-dimensional unsteady predictions of the time-averaged velocity and turbulence fields and also the predicted values of the global parameters such as the Strouhal number and the drag coefficient to close agreement with the data. Copyright © 2009 John Wiley & Sons, Ltd. [source]

On models of fractal networks

INTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 5 2009
Walter Arrighetti
Abstract A couple of iterative models for the theoretical study of fractal networks whose topologies are generated via iterated function systems is presented: a lumped-parameter impedor-oriented one and a two-port-network-oriented one. With the former, the voltage and current patterns give a detailed understanding of the electromagnetic fields' self-similar distribution throughout the network; on the other hand, model complexity exponentially increases with the prefractal iteration order. The latter ,black-box' model only controls port-oriented global parameters that are the ones commonly used in the integration of different electronic systems, and its complexity is independent of prefractal order. Sierpinski gasket and carpet topologies are reported as examples. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Deterministic radio broadcasting at low cost ,

NETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2002
Anders Dessmark
Abstract We consider distributed deterministic broadcasting in synchronous radio networks. A node receives a message in a given round if and only if exactly one of its neighbors transmits. The source message has to reach all nodes. We assume that nodes do not know the network topology or even their immediate neighborhood. (Such networks are called ad hoc.) We are concerned with two efficiency measures of broadcasting algorithms: their execution time (number of rounds) and their cost (number of transmissions). We focus our study on the execution time of algorithms which have cost close to minimum. We consider two scenarios depending on whether nodes know or do not know global parameters of the network: the number n of nodes and the eccentricity D of the source. Our main contribution is proving tight lower bounds on the time of low-cost broadcasting which show sharp differences between these scenarios. In each case, we also give broadcasting algorithms whose performance matches these lower bounds. © 2002 Wiley Periodicals, Inc. [source]