bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Specific Binding Involved in Genomic Packaging of the Double-Stranded-RNA Bacteriophage φ6
Authors: Qiao Xueying , Qiao Jian , Mindich Leonard
Published: October 2003

The genomes of bacteriophage φ6 and its relatives are packaged through a mechanism that involves the recognition and translocation of the three different plus-strand transcripts of the segmented double-stranded-RNA genomes into preformed polyhedral structures called procapsids or inner cores. The packaging requires the hydrolysis of nucleoside triphosphates and takes place in the order segment S-segment M, segment L. Packaging is dependent upon unique sequences of about 200 nucleotides near the 5′ ends of plus-strand transcripts of the three genomic segments. It appears that P1 is the determinant of the RNA binding sites. Directed mutation of P1 was used to locate regions that are important for genomic packaging. Specific binding of RNA to the exterior of the procapsid was dependent upon ATP, and a region that showed a high level of cross-linking to phage-specific RNA was located. Antibodies to peptide sequences were prepared, and their abilities to bind to the exterior of procapsids were determined. Sites sensitive to trypsin and to factor Xa were determined as well.
A study of the decomposition behaviour of 12-tungstophosphate heteropolyacid in solution
Authors: Zhu Zhirong , Tain Ruan , Rhodes Colin
Published: October 2003

In this paper, the decomposition of H3PW12O40in aqueous solution or in mixed solutions of waterethanol or wateracetone is investigated by potentiometric titration and31P NMR. Identification of the products from H3PW12O40decomposition over a pH range of 112 was achieved using preparation high performance liquid chromatography (Pre-HPLC) combined with IR, UVvis spectroscopy, and inductively coupled plasma atomic emission spectroscopy (ICP). It is found that H3PW12O40in aqueous solution decomposes in a stepwise fashion with increasing pH, with the following solution compositions: [PW12O40]3(at pH ~ 1) [Formula: see text] [PW12O40]3+ [P2W21O71]6+ [PW11O39]7(at pH 2.2) [Formula: see text] [PW12O40]3+ [P2W21O71]6+ [PW11O39]7+ [P2W18O62]6+ [P2W19O67]10(at pH 3.5) [Formula: see text] [P2W21O71]6+ [PW11O39]7+ [P2W18O62]6(at pH 5.4) [Formula: see text] [PW9O34]9(at pH 7.3) [Formula: see text] PO43+ WO42(pH > 8.3). In the first stages at pH < 8, H3PW12O40decomposes partially with removal of W=O units. In the second stage at pH > 8, tungstophosphoric completely decomposes to PO43. In contrast, the decomposition of H3PW12O40is reduced, or the stability of the [PW12O40]3anion is enhanced, in ethanolwater or acetone solution at pH < 8. Key words: 12-tungstophosphate heteropolyacid, decomposition behaviour, potentiometric titration,31P NMR, preparation high performance liquid chromatography.
Supercritical argon as a mobile phase for the flame photometric detection of sulfur
Authors: Thurbide Kevin B , Cooke Brad W
Published: October 2003

The background emission properties of supercritical argon and supercritical carbon dioxide mobile phases in packed column supercritical fluid chromatography (pSFC) with flame photometric detection (FPD) were compared. As column flow rates were increased toward common values used in pSFC, the carbon dioxide background emission grew enormously. The resulting emission spectrum displayed dominant features at wavelengths between 325 and 525 nm, consisting of a complex series of overlapping molecular emission band systems partly attributed to CO* and CH*. By comparison, when using the same flow rates with a supercritical argon mobile phase, the background emission was identical to that of the FPD flame without column effluent. In terms of intensity, when using a column flow rate of 2 mL/min, supercritical carbon dioxide contributes a background emission in the FPD that is about 3 × 105 times larger than that produced by supercritical argon. This difference leads to an improvement of two orders of magnitude in the pSFC-FPD signal-to-noise ratio for sulfur when a supercritical argon mobile phase is used. Results indicate that supercritical argon could also be advantageous for the pSFC-FPD analysis of other elements.Key words: supercritical fluid chromatography, packed column, flame photometric detection, supercritical argon.
CuO  activated carbon catalysts for methanol decomposition to hydrogen and carbon monoxide
Authors: Tsoncheva Tanya , Nickolov Radostin , Vankova Svetoslava , Mehandjiev Dimitar
Published: October 2003

A comparison of the abilities of CuO  activated carbon catalysts, prepared by different copper precursors and preparation techniques, in the methanol decomposition reaction to carbon monoxide and hydrogen was undertaken. Higher catalytic activity and stability are found for the catalysts obtained from an ammonia solution of copper carbonate. The nature of the catalytic active complex in the samples is also discussed. Key words: methanol decomposition, CuO  activated carbon catalysts, catalytic active complex.
An ionic liquid mediated Friedel-Crafts addition of arenes to isothiocyanates
Authors: Naik Prashant U , Nara Susheel J , Harjani Jitendra R , Salunkhe Manikrao M
Published: October 2003

A new protocol is developed for the synthesis of N-substituted thioamides, employing arenes and isothiocyanates in 1-butyl-3-methylimidazolium chloroaluminate ionic liquid, [bmim]Cl·2AlCl3, as a homogenous Lewis acid catalyst and solvent. The effect of Lewis acidity and the stoichiometry of the ionic liquid on the extent of product formation is studied. Studies reveal that a progressive increase in yields was observed with increasing Lewis acidity, and two equivalents of [bmim]Cl·2AlCl3 was the optimal amount for the reaction. A distinct para selectivity for the incoming thioamido group on activated arenes was observed under ambient conditions.Key words: arenes, isothiocyanates, FriedelCrafts, ionic liquids, thioamides.
On the Complexity of Commutativity Analysis
Authors: Ibarra Oscar H. , Diniz Pedro C. , Rinard Martin C.
Published: October 2003

Two operations commute if they generate the same result regardless of the order in which they execute. Commutativity is an important property — commuting operations enable significant optimizations in the fields of parallel computing, optimizing compilers, parallelizing compilers and database concurrency control. Algorithms that statically decide if operations commute can be an important component of systems in these fields because they enable the automatic application of these optimizations. In this paper we define the commutativity decision problem and establish its complexity for a variety of basic instructions and control constructs. Although deciding commutativity is, in general, undecidable or computationally intractable, we believe that efficient algorithms exist that can solve many of the cases that arise in practice.
Fault Tolerance on Star Graphs
Authors: Hu Shuo-Cheng , Yang Chang-Biau
Published: October 2003

The capability of fault tolerance is one of the advantages of multiprocessor systems. In this paper, we prove that the fault tolerance of an n-star graph is 2n-5 with restriction to the forbidden faulty set. And we propose an algorithm for examining the connectivity of an n-star graph when there exist at most 2n - 4 faults. The algorithm requires O(n2 log n) time. Besides, we improve the fault-tolerant routing algorithm proposed by Bagherzadeh et al. by calculating the cycle structure of a permutation and the avoidance of routing message to a node without any nonfaulty neighbor. This calculation needs only constant time. And then, we propose an efficient fault-tolerant broadcasting algorithm. When there is no fault, our broadcasting algorithm remains optimal. The penalty is O(n) if there exists only one fault, and the penalty is O(n2) if there exist at most n - 2 faults.
Routing on Triangles, Tori and Honeycombs
Authors: Sibeyn Jop F.
Published: October 2003

The standard n × n torus consists of two sets of axes: horizontal and vertical ones. For routing h-relations, the bisection bound gives a lower bound of h · n/4. Several algorithms nearly matching this bound have been given.

In this paper we analyze the routing capacity of modified tori: tessellations of the plane with triangles or hexagons and tori with added diagonals. On some of these networks the ratio of routing capacity and degree is higher than for ordinary tori, even though they are as easily constructed. Hence, they may constitute more cost effective alternatives.

For networks with n2 PUs, we get the following results: on a torus of hexagons, node degree 3, h-relations are performed in 0.37 · h · n steps; on a torus of triangles, node degree 6, in 0.13 · h · n; and on a torus with added diagonals, node degree 8, in h · n/12. The latter result matches the bisection bound for this network. Even faster is the routing on a torus of hexagons with diagonals, node degree 12: 0.053 · h · n.

The algorithms are simple, inspired by the algorithm of Valiant and Brebner. The results can easily be extended to sorting, dynamic routing or routing for average-case inputs.
Embedding Torus Automata into a Ring of Automata
Authors: Martin Bruno
Published: October 2003

In this paper, we deal with two-dimensional cellular automata. Our goal is to present a linear space and sub-linear time algorithm to embed a bounded finite torus, considered as a cellular space, into a ring of automata. Such an embedding has to preserve the neighborhood of the cells and to keep the periodicities of the torus. Finally, we generalize this result to torus of greater dimension.
New Routines for Algebraic Programming of the Dirac Equation
Authors: Cotăescu Ion I. , Vulcanov Dumitru N.
Published: October 2003

We present new procedures in the REDUCE language for algebraic programming of the Dirac equation on curved space-time. The main part of the program is a package of routines defining the Pauli and Dirac matrix algebras. Then the Dirac equation is obtained using the facilities of the EXCALC package. Finally we present some results obtained after running our procedures for the Dirac equation on several curved space-times.
Simulation of the Eight-Dimensional Ising Model on the Creutz Cellular Automaton
Authors: Aktekin N.
Published: October 2003

The eight-dimensional Ising model is simulated on the Creutz cellular automaton. By fitting the data for the order parameter to a power law with correction and by using the renormalization group prediction for its leading critical exponent as the criterion, the value of the critical temperature is found as Tc=14.898±0.010 at which the computed value of the leading critical exponent for the magnetic susceptibility is in agreement with the renormalization group prediction.
Comparison of Calculations for the Hubbard Model Obtained with Quantum-Monte-Carlo, Exact, and Stochastic Diagonalization
Authors: Husslein Thomas , Fettes Werner , Morgenstern Ingo
Published: October 2003

In this paper we compare numerical results for the ground state of the Hubbard model obtained by Quantum-Monte-Carlo simulations with results from exact and stochastic diagonalizations. We find good agreement for the ground state energy and superconducting correlations for both, the repulsive and attractive Hubbard model. Special emphasis lies on the superconducting correlations in the repulsive Hubbard model, where the small magnitude of the values obtained by Monte-Carlo simulations gives rise to the question, whether these results might be caused by fluctuations or systematic errors of the method. Although we notice that the Quantum-Monte-Carlo method has convergence problems for large interactions, coinciding with a minus sign problem, we confirm the results of the diagonalization techniques for small and moderate interaction strengths. Additionally we investigate the numerical stability and the convergence of the Quantum-Monte-Carlo method in the attractive case, to study the influence of the minus sign problem on convergence. Also here in the absence of a minus sign problem we encounter convergence problems for strong interactions.
Computational Force, Mass, and Energy
Authors: Numrich Robert W.
Published: October 2003

This paper describes a correspondence between computational quantities commonly used to report computer performance measurements and mechanical quantities from classical Newtonian mechanics. It defines a set of three fundamental computational quantities that are sufficient to establish a system of computational measurement. From these quantities, it defines derived computational quantities that have analogous physical counterparts. These computational quantities obey three laws of motion in computational space. The solutions to the equations of motion, with appropriate boundary conditions, determine the computational mass of the computer. Computational forces, with magnitudes specific to each instruction and to each computer, overcome the inertia represented by this mass. The paper suggests normalizing the computational mass scale by picking the mass of a register on the CRAY-1 as the standard unit of mass.
Probability of Incipient Spanning Clusters in Critical Square Bond Percolation
Authors: Shchur Lev N. , Kosyakov Sergey S.
Published: October 2003

The probability of simultaneous occurrence of at least k spanning clusters has been studied by Monte Carlo simulations on the 2D square lattice with free boundaries at the bond percolation threshold pc =1/2. It is found that the probability of k and more Incipient Spanning Clusters (ISC) have the values P(k>1) ≈ 0.00658(3) and P(k>2) ≈ 0.00000148(21) provided that the limit of these probabilities for infinite lattices exists. The probability P(k>3) of more than three ISC could be estimated to be of the order of 10-11 and is beyond the possibility to compute such a value by nowadays computers. So, it is impossible to check in simulations the Aizenman law for the probabilities when k≫1. We have detected a single sample with four ISC in a total number of about 1010 samples investigated. The probability of this single event is 1/10 for that number of samples. The influence of boundary conditions is discussed in the last section.
Experiences with a Simplified Microsimulation for the Dallas/Fort-Worth Area
Authors: Rickert M. , Nagel K.
Published: October 2003

We describe a simple framework for microsimulation of city traffic. A medium-sized excerpt of Dallas was used to examine different levels of simulation fidelity of a cellular automaton method for the traffic flow simulation and a simple intersection model. We point out problems arising with the granular structure of the underlying rules of motion.
Using Microsimulation Feedback For Trip Adaptation For Realistic Traffic In Dallas
Authors: Nagel Kai , Barrett Christopher L
Published: October 2003

This paper presents a day-to-day re-routing relaxation approach for traffic simulations. Starting from an initial planset for the routes, the route- based microsimulation is executed. The result of the microsimulation is fed into a re-router, which re-routes a certain percentage of all trips. This approach makes the traffic patterns in the microsimulation much more reasonable. Further, it is shown that the method described in this paper can lead to strong oscillations in the solutions.
Patch Algorithms in Spin Glasses
Authors: Petters Daniel
Published: October 2003

The "patch method" of Stuart Kauffman to find the approximative groundstate of a Kauffman-type model is improved by a final optimization and also modified to the groundstate of a ±J Edwards–Anderson spin glass. The method improves simple algorithms and is easily rewritten to other applications.
Quantum Lattice Gases and Their Invariants
Authors: Meyer David A.
Published: October 2003

The one-particle sector of the simplest one-dimensional quantum lattice-gas automaton has been observed to simulate both the (relativistic) Dirac and (nonrelativistic) Schrödinger equations, in different continuum limits. By analyzing the discrete analogues of plane waves in this sector we find conserved quantities corresponding to energy and momentum. We show that the Klein paradox obtains so that in some regimes the model must be considered to be relativistic and the negative energy modes interpreted as positive energy modes of antiparticles. With a formally similar approach — the Bethe ansatz — we find the evolution eigenfunctions in the two-particle sector of the quantum lattice-gas automaton and conclude by discussing consequences of these calculations and their extension to more particles, additional velocities, and higher dimensions.
Fractional Propagation and the Elimination of Staggered Invariants in Lattice-BGK Models
Authors: Qian Yue-Hong
Published: October 2003

Lattice-based models have been attracting much interest in recent years and have been applied to many complex systems. The derivation of large scale dynamical equations of lattice-gas models as well as lattice-Boltzmann models was based on the belief that only the physically interesting quantities (mass, momentum and energy) are conserved. Staggered invariants in lattice-gas models were found in 1988 and there have been no efficient methods to eliminate these invariants. In this paper, we will first discuss the existence of staggered invariants, then we propose to use fractional propagation as an effective way of suppressing these undesired invariants. Numerical simulations will be used to confirm the theory and to show the improvement of computations.
Massively Parallel Lattice-Boltzmann Simulation of Turbulent Channel Flow
Authors: Amati Giorgio , Succi Sauro , Piva Renzo
Published: October 2003

High resolution lattice-Boltzmann simulations of turbulent channel flow on the Quadrics parallel machine are presented. The parallel performance is discussed together with some preliminary results concerning the vorticity structures which appear near the wall layer and their influence on the scaling laws.
Electroviscous Transport Problems via Lattice-Boltzmann
Authors: Warren Patrick B.
Published: October 2003

The application of lattice-Boltzmann methods to electroviscous transport problems is discussed, generalising the moment propagation method for convective-diffusion problems. As a simple application, electro-osmotic flow in a parallel-sided slit is analysed, and the results compared favourably with available analytic solutions for this geometry.
Coarse-Graining of a Fluid and its Relation with Dissipative Particle Dynamics and Smoothed Particle Dynamic
Authors: Español Pep , Serrano Mar , Zuñiga Ignacio
Published: October 2003

We propose a coarse-graining procedure for a fluid system that allows us to discuss from a conceptual point of view different "mesoscopic" approaches to hydrodynamic problems. Dissipative Particle Dynamics (DPD) and Smoothed Particle Dynamics (SPS) are discussed simultaneously within this framework. In particular, we give physical meaning to the weight function used in SPD. The close analogy between DPD and SPD suggests a synthesis of both approaches that overcomes the conceptual shortcomings of both.
Patterns and Long Range Correlations in Idealized Granular Flows
Authors: Orza J. A. G. , Brito R. , van Noije T. P. C. , Ernst M. H.
Published: October 2003

An initially homogeneous freely evolving fluid of inelastic hard spheres develops inhomogeneities in the flow field u(r, t) (vortices) and in the density field n (r, t)(clusters), driven by unstable fluctuations, δa = {δn, δu}. Their spatial correlations, <δa(r, t)δa(r′,t)>, as measured in molecular dynamics simulations, exhibit long range correlations; the mean vortex diameter grows as [Formula: see text]; there occur transitions to macroscopic shearing states, etc.

The Cahn–Hilliard theory of spinodal decomposition offers a qualitative understanding and quantitative estimates of the observed phenomena. When intrinsic length scales are of the order of the system size, effects of physical boundaries and periodic boundaries (finite size effects in simulations) are important.
Heterogeneous Atomistic-Continuum Representations for Dense Fluid Systems
Authors: Hadjiconstantinou Nicolas G. , Patera Anthony T.
Published: October 2003

We present a formulation and numerical solution procedure for heterogeneous atomistic-continuum representations of fluid flows. The ingredients from atomistic and continuum perspectives are non-equilibrium molecular dynamics and spectral element, respectively; the matching is provided by a classical procedure, the Schwarz alternating method with overlapping subdomains. The technique is applied to microscale flow of a dense fluid (supercritical argon) in a complex two-dimensional channel.
Droplet Dynamics Using the Lattice-Gas Method
Authors: Hashimoto Yasuhiro , Ohashi Hirotada
Published: October 2003

We apply the lattice-gas method to study droplet behavior. The ascending velocity and deformation of a drop under buoyancy are numerically analyzed. We develop an algorithm to adjust surface tension by changing collision rules, and deformation of a droplet is calculated with different surface tensions. The deformation of a drop driven by the pressure gradient under gravity is also investigated.
Application of the SD Technique for Solving a BCS-Reduced Hubbard like Hamiltonian
Authors: Fettes Werner , Morgenstern Ingo , Husslein Thomas
Published: October 2003

We present exact and stochastic diagonalization results for a BCS-reduced Hubbard model. The kinetic Hamiltonian is the same as in the single band Hubbard model with additional next nearest neighbor hopping. The interaction of this model is designed to inhibit superconductivity in the d x2-y2 channel. The ground state of this model is studied by exact and stochastic diagonalization technique. We present a review of the technical details of the application of the stochastic diagonalization algorithm on this problem. To verify our results obtained with the stochastic diagonalization, they are compared with the exact diagonalization results. In order to show the convergence of the stochastic diagonalization we give a detailed analysis of the behavior of physical properties with increasing number of states. Finally we study superconductivity in this BCS-reduced Hubbard model. As an indicator of superconductivity we use the occurrence of Off Diagonal Long Range Order. We study the scaling behavior of this model for various attractive interactions and in addition the dependence of the superconducting correlation functions from the filling of the system.
Monte Carlo Simulation of Some Dynamical Aspects of Drop Formation
Authors: de Lima A. R. , Penna T. J. P. , de Oliveira P. M. C.
Published: October 2003

In this work we present some results from computer simulations of dynamical aspects of drop formation in a leaky faucet. Our results, which agree very well with the experiments, suggest that only a few elements, at the microscopic level, would be necessary to describe the most important features of this system. We were able to set all parameters of the model in terms of real ones. This is an additional advantage with respect to previous theoretical works.
Cluster Study in the Three-Dimensional 3-State Potts Model
Authors: Aydin M. , Çelik T. , Gündüç Y.
Published: October 2003

The three-dimensional 3-state Potts model has been investigated by examining the average cluster size distributions. Cluster distributions give evidence for the weak first-order nature of the transition for lattice sizes as small as 163, where the energy histogram method fails to exhibit the true nature of the transition.
A Simple Ansatz to Describe Thermodynamic Quantities of Peptides and Proteins at Low Temperatures
Authors: Hansmann Ulrich H. E. , de Forcrand Philippe
Published: October 2003

We describe a simple ansatz to approximate the low temperature behavior of proteins and peptides by a mean-field-like model which is analytically solvable. For a small peptide some thermodynamic quantities are calculated and compared with numerical results of an all-atoms simulation. Our approach can be used to determine the weights for a multicanonical simulation of the molecule under consideration.
Replica-Symmetric Approach to a Hidden-Layer Feature Detector
Authors: Romeo August , Ruffini Giulio
Published: October 2003

We take further the study of a learning-generalization process in a hidden-layer network for a given three-bit feature distinction by application of the replica method. When doing so, we are led to an Ising model with both external and random fields which cause considerable difficulties. Several approximations for this system are discussed
Self-Consistent Calculation of Particle-Hole Diagrams on the Matsubara Frequency: Flex Approximation
Authors: Rodríguez-Núñez J. J. , Schafroth S.
Published: October 2003

We implement the numerical method of summing Green function diagrams on the Matsubara frequency axis for the fluctuation exchange (FLEX) approximation. Our method has previously been applied to the attractive Hubbard model for low density. Here we apply our numerical algorithm to the Hubbard model close to half filling (ρ =0.40), and for T/t = 0.03, in order to study the dynamics of one- and two-particle Green functions. For the values of the chosen parameters we see the formation of three branches which we associate with the two-peak structure in the imaginary part of the self-energy. From the imaginary part of the self-energy we conclude that our system is a Fermi liquid (for the temperature investigated here), since Im Σ( k , ω) ≈ w2 around the chemical potential. We have compared our fully self-consistent FLEX solutions with a lower order approximation where the internal Green functions are approximated by free Green functions. These two approches, i.e., the fully self-consistent and the non-self-consistent ones give different results for the parameters considered here. However, they have similar global results for small densities.
Diffusion Phenomena and Other WWW Applications for An Introductory Physics Course
Authors: Cattani G. , Coperchio M. C. , Navarria F.-L. , Rovelli T.
Published: October 2003

The World Wide Web originated within the high-energy physics community from the need to exchange documentation in an efficient way. It can be used easily to produce and maintain didactic material for teaching physics. The material can be made accessible via the network in hypertext form, comprising text, pictures, animations, audio files. For didactic applications in physics, the capability of an interactive link, beyond the use of simple electronic forms is necessary. This was not foreseen in the original WWW protocol, and it has been developed in an application presented here to simulate a series of measurements in a diffusion process in solutions. The recent introduction of the Java language offers a natural way to create new powerful interactive Internet applications. We are currently developing and testing Java powered didactic applications.
Numerical Study of Dip Formation Using Sink Array Model
Authors: Kim Min-Joon
Published: October 2003

We studied dip formation phenomena in a draining water tank using the model of sink arrays. As the parameter for the drain size r increases, the effective Froude number F eff is found to decrease according to F eff /F=r-∊ where F is the Froude number defined as F=q0/[2π(gh3)1/2] and ∊ is a constant. Here, q0 is the total sink strength, h is the submerged depth of the sink array, and g is the gravitational acceleration. For F=0.286, ∊ is found to be ∊ ≈ 0.44. The implications of the results are discussed.
Difference Approximations at Internal Physical Boundaries
Authors: Ali Farhad
Published: October 2003

Two sample difference approximations at internal physical boundaries, in magnetic field calculations, are analyzed in the light of truncation and discretization error expansions. Existence of asymptotic expansions for discretization error and their use in error estimation is studied in the light of approximations of the resulting variational equations. Two test problems are presented to illustrate validity of the error analysis. Better difference approximations are shown to lead to better approximation of the associated variational equations.
ab initio LCAO Calculations of Small Helium Clusters
Authors: Mazzone A. M.
Published: October 2003

He clusters represent an anomalous case in the field of nanosized structures owing to the extremely low value of the temperature of the liquid phase in bulk helium. The weak dissipative forces which hold these clusters together offer a severe benchmark for calculations of all types. Owing to the interest in phenomena of superfluidity and superconductivity, calculation methods, optimized from either the computational or the mathematical point of view, are the object of very intensive efforts. In this study we report calculations of the structure and energetics of small He clusters obtained by using a LCAO method of the ab initio type with simple trial functions of the gaussian type. The results indicate that the cluster structure is correctly predicted, though deep spurious minima in the energy potential surface are also found.
FFT for the APE Parallel Computer
Authors: Lippert Thomas , Schilling Klaus , Trentmann Sven , Toschi Federico , Tripiccione Raffaele
Published: October 2003

We present a parallel FFT algorithm for SIMD systems following the "Transpose Algorithm" approach. The method is based on the assignment of the data field onto a one-dimensional ring of systolic cells. The systolic array can be universally mapped onto any parallel system. In particular for systems with next-neighbor connectivity our method has the potential to improve the efficiency of matrix transposition by use of hyper-systolic communication. We have realized a scalable parallel FFT on the APE100/Quadrics massively parallel computer, where our implementation is part of a two-dimensional hydrodynamics code for turbulence studies.
Numerical Approach to Statistical Mechanics of Surfactants in Porous Media: A Coarse Grained Description
Authors: Maiti Prabal K. , Chowdhury Debashish
Published: October 2003

We present a numerical scheme for Monte Carlo Simulation (MC) of ternary microemulsions, which consist of oil, water and surfactants, confined inside a porous medium such as vycor glass. The model porous medium has been created using the Cell Dynamical Scheme (CDS) while the microemulsion has been modeled following the Larson prescription.
Dynamic Predictions from Time Series Data — An Artificial Neural Network Approach
Authors: Kulkarni D. R. , Parikh J. C. , Pandya A. S.
Published: October 2003

A hybrid approach, incorporating concepts of nonlinear dynamics in artificial neural networks (ANN), is proposed to model a time series generated by complex dynamic systems. We introduce well-known features used in the study of dynamic systems — time delay τ and embedding dimension d — for ANN modeling of time series. These features provide a theoretical basis for selecting the optimal size for the number of neurons in the input layer. The main outcome of the new approach for such problems is that to a large extent it defines the ANN architecture, models the time series and gives good prediction. As a consequence, we have an integrated and systematic data-driven scheme for modeling time series data. We illustrate our method by considering computer generated periodic and chaotic time series. The ANN model developed gave excellent quality of fit for the training and test sets as well as for iterative dynamic predictions for future values of the two time series. Further, computer experiments were conducted by introducing Gaussian noise of various degrees in the two time series, to simulate real world effects. We find that up to a limit introduction of noise leads to a smaller network with good generalizing capability.
The Trigger of the ATLAS Experiment
Authors: Schörner-Sadenius Thomas
Published: October 2003

With the high bunch-crossing and interaction rates and potentially large event sizes, the experiments at the LHC challenge data acquisition and trigger systems. Within the ATLAS experiment, a multi-level trigger system based on hardware and software is employed to cope with the task of event-rate reduction. This review gives an overview of the trigger of the ATLAS experiment highlighting the design principles and the implementation of the system and provides references to more detailed information. In addition, first trigger-performance studies and an outlook on the ATLAS event-selection strategy are presented.
Polaron Energy Spectrum in a Disk-Shaped Quantum Dot
Authors: Alekperov O. Z. , Guseinov N. M.
Published: October 2003

The energy spectrum of a weak coupling polaron is considered in a disk-shaped quantum dot. An analytical expression for the polaron energy correction to the ground and the first excited state is calculated using a modified pertubation theory. Anticrossing of the polaron energy levels in the dependence on the quantum dot radius is obtained.
Steady-State Characteristics of Switched-Capacitor Electronic Converters
Authors: Zhu GuangYong , Ioinovici Adrian
Published: October 2003

By performing a detailed analysis of switching-mode power supplies based on swithed-capacitor circuits, their fundamental steady-state characteristics are found. A few basic step-down and step-up converters are considered. No approximations, such a averaging techniques are required. The on-resistances of the transistors, forward voltages of the diodes and equivalent-series resistances of capacitors are taken into account. Design-oriented formulas of the DC voltage ratio, trade-offs allowing for the best possible efficiency, the smallest possible ripple and the best possible line and load regulation give the design values of the number of capacitors in the switched-capacitor circuit, of their capacitances and of the switching frequency.
Voice and Telephony Over ATM for Multimedia Network using Shared VCI Cell
Authors: Masaki Toshihiro , Nakatani Yasuhiro , Onoye Takao , Murakami Koso
Published: October 2003

This paper presents new multimedia Asynchronous Transfer Mode (ATM) networks which are capable of transmitting voice data efficiently and serving smooth evolution from the existing narrowband voice networks. Fully ATMized networks are characterized by having both rerouting function and switching function. The rerouting nodes multiplex plural calls going through the same route into one ATM cell, namely shared virtual channel identifier (VCI) cell. The shared VCI cell includes fellow cells which contain call data and its VCI. The rerouting node is integrated into a single chip by using CMOS technology. The multimedia ATM networks can be readily implemented by attaching the rerouting nodes to the standard ATM switches.
Perfect Multivariable Feedback Theory
Authors: Tong M.-D. , Chen W.-K.
Published: October 2003

The paper nicely combines the state-space description with the input-output description and elegantly formulates the multivariable feedback theory as well as obtains a number of useful results for modern network and control theory. In particular, it reveals various kinds of duality between a multivariable feedback network and its associated inverse network, such as structure duality, transfer function matrix (determinant) duality and duality on controllability (observability). It also thoroughly studies four pairs of the (null) return difference matrices of a multivariable feedback network and its associated inverse network, and presents not only the dual properties about these (null) return diferrence matrices and their respective determinants, but also treats the relationships among these determinants, the characteristic polynomials of a closed-loop network (the multivariable feedback network), its associated closed-loop inverse network, and their respective corresponding open-loop networks. Finally, the stability criteria, the testing criteria for a minimum-phase matrix and the sensitivity matrices are discussed. Although all of these results are obtained for a continuous system, they are also suitable for a discrete system provided that we use the z-transformation instead of the Laplace transformation.
Multiplier-Free IIR Filter Realizations with Periodically Time-Varying Coefficients
Authors: Tantaratana Sawasd
Published: October 2003

In this paper, the periodically time-varying (PTV) structure, previously proposed for realizing FIR filters, is extended to IIR filter realization. The realization consists of ternary ({0, ±1}) or quinary ({0, ±1, ±2}) PTV coefficients with simple input and output units. Coefficient multiplications as well as the input and output units require no hardware multiplier, which helps increase the processing speed or reduce the chip area. Bit-level architectures are presented. The regularity and local interconnection of the architectures help simplify VLSI design and layout.
Recovery of Phase Using Power Spectrum and Bispectrum
Authors: Takaya Kunio
Published: October 2003

Theoretically, recovery of phase from power spectrum is possible only for minimum phase signals. When a signal is either known to be of minimum phase or the analysis requiring phase information can accept the phase estimated by regarding the signal as a minimum phase signal, a simple method presented here can calculate the phase easily from the power spectrum. If a signal is a decaying signal approaching zero, the signal can be extended to its double length by padding zeros. The zero-padded portion of such double length data can be taken as a result of cancellation between two double length odd and even signals. Symmetry and anti-symmetry associated with the DFT of even data and odd data makes the recovery of the phase possible. Methods of deconvolution to reconstruct the original spectrum from the spectrum of the zero padded double length data is also discussed. Phase recovery not restricted to the minimum phase depends on the bispectrum, which is the Fourier transform of the third order cummulant. An algorithm that estimates phase from the bispectrum was studied for its robustness and efficiency and compared with the phase estimation directly from the power spectrum.
IR Model of 3D Aircraft for Simulation of Reticle Seekers
Authors: Hong Hyun-Ki , Han Sung-Hyun , Hong Gyoung-Pyo , Jahng Surng-Gabb , Choi Jong-Soo
Published: October 2003

This paper presents an efficient simulation method that generates thermal images and also gives tracking results of infra-red (IR) reticle seekers. First, we make an IR model of the object with the internal heat source, and generate thermal images by the optical system of the reticle seeker and the atmospheric turbulence. Using the obtained thermal images, we can simulate IR reticle seekers in various scenarios including countermeasures (CM) such as flares. Simulation results show that we can generate more accurate images by using the proposed method, which is applicable to the study of the development of counter-countermeasures (CCMs).
Event-Driven Power Estimation of CMOS Circuits
Authors: Tsai Wei-Chang , Shung C. Bernard
Published: October 2003

Fast and accurate power estimation has become an important topic with the increasing need for low power electronics. In this paper we address the problem of using event-driven simulation tools for power estimation. We identify and compare two approaches: input-driven and output-driven, and propose several ways of improvement. The estimation accuracy is degraded in event-driven power estimators due to superfluous and partial glitches. We described glitch filtering and estimation techniques pertaining to input-driven and output-driven power estimators. An output-driven power estimator, Peony, was developed which used the proposed path power idea to improve the estimation accuracy. It achieved significant power estimation accuracy improvement at a speed of two orders of magnitude faster than Spice.
Accommodating Linear and Nonlinear Boundary Conditions in Wave Digital Simulations of PDE Systems
Authors: Xu Cathy Qun , Bass Steven C. , Wang Xiaoming
Published: October 2003

The Wave Digital multidimensional discretization technique, recently proposed by A. Fettweis et al., is a potentially important new method for simulating systems of partial differential equations (PDEs), especially those that model processes appearing in nature. To date, no general method has appeared in the literature indicating how to accommodate boundary conditions in Wave Digital simulations. Since the incorporation of a consistent set of boundary conditions within a given PDE system is a necessary condition for that system even to possess a unique solution, it is clear that accounting for boundary conditions within numeric simulations is just as necessary. We present here a method for accommodating lumped, linear or nonlinear boundary conditions into the Wave Digital simulation of either linear or nonlinear PDE systems. Graphic results from the Wave Digital simulation of a simple acoustics problem are also given.
Tangle Equations II
Authors: Ernst C.
Published: October 2003

Given two 4-plats K1 and K2. Let O be a sum of rational tangles such that N(O+P)=K1 and N(O+R)=K2, where P and R are rational tangles and N is the numerator construction on the tangles O+P and O+R, respectively. An algorithm is presented here to solve such a system of equations for O, P and R in the case where O is non rational. If two additional equations of the form N(O+R+R)=K3 and N(O+R+R+R+) =K4 are given and one of the Ki is chiral, then there is at most one solution for O and R. If all Ki are achiral then there is at most one solution together with its mirror image.
TQFT and Whitehead's Manifold
Authors: Funar Louis
Published: October 2003

The aim of this note is to give two applications of Topological Quantum Field Theories to the topology of open manifolds. The invariants we derived may be used to test if an open manifold is simply connected at infinity (as we did for Whitehead's manifold in case of the sl2(C)-TQFT in level 3) or to construct examples of non-homeomorphic contractible open 3-manifolds.
The Writhe of Knots in the Cubic Lattice
Authors: Janse Van Rensburg E. J. , Orlandini E. , Sumners D. W. , Tesi M. C. , Whittington S. G.
Published: October 2003

The writhe of a knot in the simple cubic lattice [Formula: see text] can be computed as the average linking number of the knot with its pushoffs into four non-antipodal octants. We use a Monte Carlo algorithm to generate a sample of lattice knots of a specified knot type, and estimate the distribution of the writhe as a function of the length of the lattice knots. If the expected value of the writhe is not zero, then the knot is chiral. We prove that the writhe is additive under concatenation of lattice knots and observe that the mean writhe appears to be additive under the connected sum operation. In addition we observe that the mean writhe is a linear function of the crossing number in certain knot families.
On Kauffman Brackets
Authors: Zhu Jun
Published: October 2003

An antichain is associated to each link diagram so that the highest degree of the Kauffman bracket can be determined. As an application, we show that the span of the Kauffman bracket is less than or equal to 4(n - m) for dealternator connected m-alternating diagrams and the upper bound is best possible. This completely solves a conjecture of [1]. Finally, we show that a semi-alternating diagram may be not a minimal diagram which disproves a conjecture of K. Murasugi [10].
Stick Numbers and Composition of Knots and Links
Authors: Adams Colin C. , Brennan Bevin M. , Greilsheimer Deborah L. , Woo Alexander K.
Published: October 2003

We address the concept of stick number for knots and links under various restrictions concerning the length of the sticks, the angles between sticks, and placements of the vertices. In particular, we focus on the effect of composition on the various stick numbers. Ultimately, we determine the traditional stick number for an infinite class of knots, which are the (n,n-1)-torus knots together with all of the possible compositions of such knots. The exact stick number was previously known for only seven knots.
A Combinatorial Link Invariant of Finite Type Derived from Chern-Simons Theory
Authors: Hirshfeld Allen C. , Sassenberg Uwe , Klöker Thomas
Published: October 2003

We derive from the perturbation expansion of the Wilson loop expectation value in the Chern-Simons theory an explicit combinatorial expression for a third-order finite link invariant, thereby generalising the knot invariant considered in a previous article.
On Finiteness of Certain Vassiliev Invariants
Authors: Kauffman Louis H. , Saito Masahico , Sawin Stephen F.
Published: October 2003

The best known examples of Vassiliev invariants are the coefficients of a Jones-type polynomial expanded after exponential substitution. We show that for a given knot, the first N Vassiliev invariants in this family determine the rest for some integer N.
Cabling the Vassiliev Invariants
Authors: Kricker A. , Spence B. , Aitchison I.
Published: October 2003

We characterise the cabling operations on the weight systems of finite type knot invariants. The eigenvectors and eigenvalues of this family of operations are described. The canonical deframing projection for these knot invariants is described over the cable eigenbasis. The action of immanent weight systems on general Feynman diagrams is considered, and the highest eigenvalue cabling eigenvectors are shown to be dual to the immanent weight systems. Using these results, we prove a recent conjecture of Bar-Natan and Garoufalidis on cablings of weight systems.
On Singular Braids
Authors: Zhu Jun
Published: October 2003

In Vassiliev theory, there is a natural monoid homomorphism from n-strand singular braids to the group algebra of n-strand braid group. J. Birman conjectured that this monoid homomorphism is injective. We show that the monoid homomorphism is injective on braids with up to three singularities and that Birman's conjecture is equivalent to that singular braids are distinguishable by Vassiliev braid invariants.
Ohtsuki's Invariants are of Finite Type
Authors: Krickerr A. , Spence B.
Published: October 2003

Using a vanishing condition on certain combinations of components of the Jones polynomial for algebraically split links we show that Ohtsuki's invariants of integral homology three spheres are of finite type. We further show that the corresponding manifold weight system is given by the expected Lie algebraic construction.
Generalized Braid Groups and Mapping Class Gropus
Authors: Labruere C.
Published: October 2003

Given a chord system of D2, we associate a generalized braid group, a surface and a homomorphism from this braid group to the mapping class group of the surface. We disprove a conjecture stated in an article by Perron and Vannier by showing that generally this homomorphism is not injective.
Nonsingular Configurations of 7 Lines of IRP3
Authors: Borobia Alberto , Mazurovskiĭ Vladimir F.
Published: October 2003

A nonsingular configuration of m lines of ℝP3 is defined as an (unordered) collection of m nonoriented pairwise disjoint lines in ℝP3. An isotopy of such a collection in the process of which the lines remain pairwise disjoint lines is called a rigid isotopy. The main aim of the paper is to classify nonsingular configurations of 7 lines of ℝP3 up to rigid isotopy.
Evolution of Coupling Constant in Hot QCD
Authors: Chaichian M. , Hayashi M.
Published: October 2003

The evolution of QCD coupling constant at finite temperature is considered by making use of the finite temperature renormalization group equation up to the one-loop order in the background field method with the Feynman gauge and the imaginary time formalism. The results are compared with the ones obtained in the literature. We point out, in particular, the origin of the discrepancies between different calculations, such as the choice of gauge, the breakdown of Lorentz invariance, imaginary versus real time formalism and the applicability of the Ward identities at finite temperature.
Mechanism of Inelastic Collisions of Oxygen at 3.2 TeV with Different Emulsion Targets
Authors: El-Nadi M. , El-Nagdy M. S. , Shaat E. A. , Abou-Moussa Z. , Kamel S. , Abdalla A. M.
Published: October 2003

This work investigates the main characteristic multiplicities of various types of secondary particles and correlations between them in the interaction of 16 O with emulsion at 200 GeV per nucleon. Statistically the collisions due to light nuclei (H,C,N,O) and heavy nuclei (Ag, Br) were separated. The characteristics for each group were studied.