bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic Model for Spade Drills for Wood Drilling Operations, Part 1: Model Development
Authors: Zhao Hanxin , Ehmann Kornel F.
Published: April 2003

The purpose of this work is to present an investigation of the force system generated during spade drill-bit drilling processes that is a prerequisite for the design of spade-drills with improved performance. The technical literature offers no references to this type of bit and process; hence an approach based on the well-established mechanistic force prediction methods will be used. The force and torque prediction models are based on a complete analytical model of a generalized spade bit that takes into account the cutting action of all the characteristic cutting edges of the spade bit, namely of its chisel edge, tip and major cutting edges. In conjunction with the model an efficient model calibration method is also introduced and experimentally verified.
Analytical Prediction of the Chip Back-Flow Angle in Machining With Restricted Contact Grooved Tools
Authors: Fang N. , Jawahir I. S.
Published: April 2003

This paper develops a new analytical model to predict the chip back-flow angle in machining with restricted contact grooved tools. The model is derived from a recently established universal slip-line model for machining with restricted contact cutaway tools. A comprehensive definition of the chip back-flow angle is presented first, and based on this, a quantitative analysis of the chip back-flow effect is established for a given set of cutting conditions, tool geometry, and variable tool-chip interfacial stress state. The model also predicts the cutting forces, the chip thickness, and the chip up-curl radius. A full experimental validation of the analytical predictive model involving the use of high speed filming technique is then presented for the chip back-flow angle. This validation provides a range of feasible/prevalent tool-chip interfacial frictional conditions for the given set of input conditions.
Finite Element Investigation of Friction Condition in a Backward Extrusion of Aluminum Alloy
Authors: Im Yong-Taek , Kang Seong-Hoon , Cheon Jae-Seung
Published: April 2003

Finite element simulations are being widely used to increase the efficiency and effectiveness of design of bulk metal forming processes. In such simulations, proper consideration of friction condition is important in obtaining reliable results. For this purpose, the shear friction factor is widely used for bulk deformation analyses. In the earlier work, it was found that a radial tip was formed on the extruded end of the workpiece and that the radial tip distance had a linear relationship with the forming load in the tip test. In order to characterize the global average shear friction factor, a linear relationship between the nondimensionalized radial tip distance and shear friction factor was numerically determined in this study for AL6061-O for various lubrication conditions. The global average friction condition at the bottom die interface was determined to be about 60 percent of the one at the punch in the backward extrusion under the present conditions.
Analysis of Tube Hydroforming by Means of an Inverse Approach1
Authors: Nguyen Ba Nghiep , Johnson Kenneth I. , Khaleel Mohammad A.
Published: April 2003

This paper presents a computational tool for the analysis of freely hydroformed tubes by means of an inverse approach. The formulation of the inverse method developed by Guo et al. [1] is adopted and extended to the tube hydroforming problems in which the initial geometry is a round tube submitted to hydraulic pressure and axial feed at the tube ends (end-feed). A simple criterion based on a forming limit diagram is used to predict the necking regions in the deformed workpiece. Although the developed computational tool is a stand-alone code, it has been linked to the Marc finite element code for meshing and visualization of results. The application of the inverse approach to tube hydroforming is illustrated through the analyses of the aluminum alloy AA6061-T4 seamless tubes under free hydroforming conditions. The results obtained are in good agreement with those issued from a direct incremental approach. However, the computational time in the inverse procedure is much less than that in the incremental method.
Axons Guided by Insulin Receptor in
Drosophila
Visual System
Authors: Song Jianbo , Wu Lingling , Chen Zun , Kohanski Ronald A. , Pick Leslie
Published: April 2003

Insulin receptors are abundant in the central nervous system, but their roles remain elusive. Here we show that the insulin receptor functions in axon guidance. The
Drosophila
insulin receptor (DInR) is required for photoreceptor-cell (R-cell) axons to find their way from the retina to the brain during development of the visual system. DInR functions as a guidance receptor for the adapter protein Dock/Nck. This function is independent of Chico, the
Drosophila
insulin receptor substrate (IRS) homolog.
Regulation of Elongating RNA Polymerase II by Forkhead Transcription Factors in Yeast
Authors: Morillon Antonin , O'Sullivan Justin , Azad Abul , Proudfoot Nicholas , Mellor Jane
Published: April 2003

The elongation phase of transcription by RNA polymerase II (RNAPII) is highly regulated and tightly linked to pre–messenger RNA (pre-mRNA) processing. Recent studies have implicated an early elongation checkpoint that facilitates the link to pre-mRNA processing. Here we show that the yeast forkhead transcription factors, Fkh1p and Fkh2p, associate with the coding regions of active genes and influence, in opposing ways, transcriptional elongation and termination. These events are coordinated with serine-5 and -2 phosphorylation of the heptad repeat of the carboxy-terminal domain (CTD) of RNAPII. Our results suggest that, in addition to their documented promoter function, Fkh1p and Fkh2p coordinate early transcription elongation and pre-mRNA processing. This may reflect a general feature of gene regulation in eukaryotes.
Multifunctional Alloys Obtained via a Dislocation-Free Plastic Deformation Mechanism
Authors: Saito Takashi , Furuta Tadahiko , Hwang Jung-Hwan , Kuramoto Shigeru , Nishino Kazuaki , Suzuki Nobuaki , Chen Rong , Yamada Akira , Ito Kazuhiko , Seno Yoshiki , Nonaka Takamasa , Ikehata Hideaki , Nagasako Naoyuki , Iwamoto Chihiro , Ikuhara Yuuichi , Sakuma Taketo
Published: April 2003

We describe a group of alloys that exhibit “super” properties, such as ultralow elastic modulus, ultrahigh strength, super elasticity, and super plasticity, at room temperature and that show Elinvar and Invar behavior. These “super” properties are attributable to a dislocation-free plastic deformation mechanism. In cold-worked alloys, this mechanism forms elastic strain fields of hierarchical structure that range in size from the nanometer scale to several tens of micrometers. The resultant elastic strain energy leads to a number of enhanced material properties.
The Onset of Matter-Wave Amplification in a Superradiant Bose-Einstein Condensate
Authors: Schneble Dominik , Torii Yoshio , Boyd Micah , Streed Erik W. , Pritchard David E. , Ketterle Wolfgang
Published: April 2003

The interaction of short and strong laser pulses with an atomic Bose-Einstein condensate is found to generate patterns of recoiling atoms that are different from those seen in previous light-scattering experiments. This phenomenon can only be explained by optical stimulation, showing that the previous description of superradiance as atomic stimulation is incomplete and that matter-wave amplification in Bose-Einstein condensates is suppressed at short times. Our experiments clarify the nature of bosonic stimulation in the four-wave mixing of light and atoms.
Induction of Tumors in Mice by Genomic Hypomethylation
Authors: Gaudet François , Hodgson J. Graeme , Eden Amir , Jackson-Grusby Laurie , Dausman Jessica , Gray Joe W. , Leonhardt Heinrich , Jaenisch Rudolf
Published: April 2003

Genome-wide DNA hypomethylation occurs in many human cancers, but whether this epigenetic change is a cause or consequence of tumorigenesis has been unclear. To explore this phenomenon, we generated mice carrying a hypomorphic DNA methyltransferase 1 (
Dnmt1
) allele, which reduces Dnmt1 expression to 10% of wild-type levels and results in substantial genome-wide hypomethylation in all tissues. The mutant mice were runted at birth, and at 4 to 8 months of age they developed aggressive T cell lymphomas that displayed a high frequency of chromosome 15 trisomy. These results indicate that DNA hypomethylation plays a causal role in tumor formation, possibly by promoting chromosomal instability.
PARALLEL PREDICTOR-CORRECTOR METHODS FOR THE SOLUTION OF ORDINARY DIFFERENTIAL EQUATIONS II
Authors: MAZZONE A. M.
Published: April 2003

This work presents parallel multistep methods for the solution of ordinary differential equations. The characteristic of parallel computing is that there is a "front" and the computation at points ahead of the front depends only on information behind it. This requires a resetting of serial algorithms and may also lead to numerical errors and instabilities. The analysis of positive and negative aspects of parallel computing is the subject of this paper. Some of the methods presented below are uncommon in the literature on mathematical computing. Others have been elaborated for this study on the basis of the traditional Adams-Bashforth multistep methods.

A performance comparison of the methods is made by numerical testing in molecular dynamics calculations. The increase of the number of processors m appears to seriously deteriorate the stability of the calculations and the use of m larger than 2 seems impractical.
CHARACTERIZATION OF ASYMMETRIC FRAGMENTATION PATTERNS IN SPATIALLY EXTENDED SYSTEMS
Authors: ROSA R. R. , SHARMA A. S. , VALDIVIA J. A.
Published: April 2003

Spatially extended systems yield complex patterns arising from the coupled dynamics of its different regions. In this paper we introduce a matrix computational operator, [Formula: see text], for the characterization of asymmetric amplitude fragmentation in extended systems. For a given matrix of amplitudes this operation results in an asymmetric-triangulation field composed by L points and I straight lines. The parameter (I-L)/L is a new quantitative measure of the local complexity defined in terms of the asymmetry in the gradient field of the amplitudes. This asymmetric fragmentation parameter is a measure of the degree of structural complexity and characterizes the localized regions of a spatially extended system and symmetry breaking along the evolution of the system. For the case of a random field, in the real domain, which has total asymmetry, this asymmetric fragmentation parameter is expected to have the highest value and this is used to normalize the values for the other cases. Here, we present a detailed description of the operator [Formula: see text] and some of the fundamental conjectures that arises from its application in spatio-temporal asymmetric patterns.
MULTI-PROCESSOR MOLECULAR DYNAMICS USING THE BRENNER POTENTIAL: PARALLELIZATION OF AN IMPLICIT MULTI-BODY POTENTIAL
Authors: ROSENBLUM IRINA , ADLER JOAN , BRANDON SIMON
Published: April 2003

We present computational aspects of Molecular Dynamics calculations of thermal properties of diamond using the Brenner potential. Parallelization was essential in order to carry out these calculations on samples of suitable sizes. Our implementation uses MPI on a multi-processor machine such as the IBM SP2. Three aspects of parallelization of the Brenner potential are discussed in depth. These are its long-range nature, the need for different parallelization algorithms for forces and neighbors, and the relative expense of force calculations compared to that of data communication. The efficiency of parallelization is presented as a function of different approaches to these issues as well as of cell size and number of processors employed in the calculation. In the calculations presented here, information from almost half of the atoms were needed by each processor even when 16 processors were used. This made it worthwhile to avoid unnecessary complications by making data from all atoms available to all processors. Superlinear speedup was achieved for four processors (by avoiding paging) with 512 atom samples, and 5ps long trajectories were calculated (for 5120 atom samples) in 53 hours using 16 processors; 514 hours would have been needed to complete this calculation using a serial program. Finally, we discuss and make available a set of routines that enable MPI-based codes such as ours to be debugged on scalar machines.
A MONTE CARLO STUDY OF THE SPECIFIC HEAT OF DILUTED ANTIFERROMAGNETS
Authors: STAATS M. , USADEL K. D.
Published: April 2003

The three-dimensional diluted antiferromagnet in a magnetic field has a longe-range ordered state for sufficiently low temperatures and external fields. We study the irreversibilities at the phase transition from this state into the paramagnetic state at higher temperatures. Performing field cooling and zero field cooling simulation procedures we find a small irreversibility in the internal energy and the specific heat, although the behavior of the order parameter is irreversible and the phase transition is suppressed in the FC case. The specific heat shows a noncritical broad maximum above the transition temperature Tc. The results are compatible with recent experimental results obtained by Satooka et al., whereas our interpretation of the data is different.
MOLECULAR DYNAMICS SIMULATIONS OF LIQUID CRYSTAL ANCHORING AT AN AMORPHOUS POLYMER SURFACE
Authors: DOERR T. P. , TAYLOR P. L.
Published: April 2003

Atomistic molecular dynamics simulations have been used, apparently for the first time, to investigate the anchoring behavior of a liquid crystal at the interface with an amorphous polymer. The simulations studied a system consisting of the nematogen 5CB at the surface of amorphous polyethylene, and used the simple Dreiding II force field. The simulations indicate a preference for nonplanar anchoring. Two distinct microscopic paths have been identified by which the liquid crystal changes orientation at the surface. In one case, only one or a few of the 5CB molecules are rotating at any particular time. In the other case, a substantial fraction of the molecules rotate simultaneously.
THE ORIENTATIONAL AND STRUCTURAL PROPERTIES OF N2 and N2–AR SOLIDS AT HIGH PRESSURE
Authors: VAN KLAVEREN E. P. , MICHELS J. P. J. , SCHOUTEN J. A.
Published: April 2003

The high pressure phases of N 2 and N 2–Ar mixed solids at 7 GPa have been investigated using Monte Carlo simulations. Orientational order parameters and displacements of the molecules with respect to the positions of the space group were calculated. These tools provide an appropriate way to study these solids. In the ε* phase, the displacement Δ of the e sites was found to be 0.05 Å. In the [Formula: see text] phase, the orientational confinement to a disk of the N 2 molecules at the c sites increases with Ar concentration. Within this disk, the distribution is nonuniform, even at high temperatures. The orientationally ordered disk molecules show a displacement along the line of closest intermolecular contact. For the tetragonal modification of the [Formula: see text] phase, the c axis is perpendicular to these ordered and displaced disks. At high Ar concentrations, the [Formula: see text] phase shows a large degree of alignment of the disk molecules. In this phase, the equilibrium positions show a complicated structure. Therefore, there are small but significant structural changes between the [Formula: see text], [Formula: see text] and [Formula: see text] phases.
LIQUID CRYSTAL MODELING: ELECTROSTATIC AND VAN DER WAALS INTERACTION ENERGIES FOR MOLECULAR BUILDING BLOCKS FROM BENZENE TO CHOLESTEROL
Authors: BRAUN BELINDA , HOHLA MANFRED , KÖHLER JUTTA
Published: April 2003

Intermolecular interaction energies for molecular dimers of benzene, indene, naphthalene, phenanthrene, cholesterol and glycyrrhetinic acid have been calculated according to the CVFF empirical force field of the DISCOVER program. The parallel orientations (side by-side) turned out to be the energetically most favourable ones, in agreement with the parametrization of Gay–Berne potentials. The energies of the T-shape and in-plane (end-to-end) orientations of the entirely asymmetric molecules cholesterol and glycyrrhetinic acid depend strongly on the actual atomic positions. This shows the extent to which the shape and charges of molecules determine all possible orientations and interaction energies in molecular ensembles.
MONTE CARLO SIMULATIONS OF ROD-LIKE GAY–BERNE MESOGENS WITH TRANSVERSE DIPOLES
Authors: BERARDI ROBERTO , ORLANDI SILVIA , ZANNONI CLAUDIO
Published: April 2003

We report the results of a Monte Carlo investigation of a system of rod-like particles interacting via the Gay–Berne potential with an embedded transverse dipole. We describe the effect that the dipole has on the molecular organization.
UNSPLITTING BGK-TYPE SCHEMES FOR THE SHALLOW WATER EQUATIONS
Authors: XU KUN
Published: April 2003

As a continuation of the research on BGK-type schemes, we present in this paper a second-order unsplitting method for the shallow water equations, where the source terms are included explicitly in the time-dependent flux functions across the cell interface.
FINANCIAL "ANTI-BUBBLES": LOG-PERIODICITY IN GOLD AND NIKKEI COLLAPSES
Authors: JOHANSEN A. , SORNETTE D.
Published: April 2003

We propose that the herding behavior of traders leads not only to speculative bubbles with accelerating over-valuations of financial markets possibly followed by crashes, but also to "anti-bubbles" with decelerating market devaluations following all-time highs. For this, we propose a simple market dynamics model in which the demand decreases slowly with barriers that progressively quench in, leading to a power law decay of the market price characterized by decelerating log-periodic oscillations. We document this behavior of the Japanese Nikkei stock index from 1990 to present and of the gold future prices after 1980, both after their all-time highs. We perform simultaneously parametric and nonparametric analyses that are fully consistent with each other. We extend the parametric approach to the next order of perturbation, comparing the log-periodic fits with one, two and three log-frequencies, the latter providing a prediction for the general trend in the coming years. The nonparametric power spectrum analysis shows the existence of log-periodicity with high statistical significance, with a preferred scale ratio of λ≈3.5 for the Nikkei index and λ≈1.9 for the Gold future prices, comparable to the values obtained for speculative bubbles leading to crashes.
MODELING DISORDERED QUANTUM SYSTEMS WITH DYNAMICAL NETWORKS
Authors: KLESSE ROCHUS , METZLER MARCUS
Published: April 2003

It is the purpose of the present article to show that so-called network models, originally designed to describe static properties of disordered electronic systems, can be easily generalized to quantum-dynamical models, which then allow for an investigation of dynamical and spectral aspects. This concept is exemplified by the Chalker–Coddington model for the quantum Hall effect and a three-dimensional generalization of it. We simulate phase coherent diffusion of wave packets and consider spatial and spectral correlations of network eigenstates as well as the distribution of (quasi-)energy levels. Apart from that, it is demonstrated how network models can be used to determine two-point conductances. Our numerical calculations for the three-dimensional model at the Metal-Insulator transition point delivers, among others, an anomalous diffusion exponent of η=3-D2=1.7±0.1. The methods presented here in detail have been used partially in earlier work.
SOLVING THE SCHRÖDINGER EQUATION FOR BOUND STATES WITH MATHEMATICA 3.0
Authors: LUCHA WOLFGANG , SCHÖBERL FRANZ F.
Published: April 2003

Using Mathematica 3.0, the Schrödinger equation for bound states is solved. The method of solution is based on a numerical integration procedure together with convexity arguments and the nodal theorem for wave functions. The interaction potential has to be spherically symmetric. The solving procedure is simply defined as some Mathematica function. The output is the energy eigenvalue and the reduced wave function, which is provided as an interpolated function (and can thus be used for the calculation of, e.g., moments by using any Mathematica built-in function) as well as plotted automatically. The corresponding program schroedinger.nb can be obtained from franz.schoeberl@univie.ac.at.
EFFECT OF THE NUMBER OF ENERGY LEVELS OF A DEMON ON THE SIMULATION OF THE ISING MODELS IN FIVE TO SEVEN DIMENSIONS ON THE CREUTZ CELLULAR AUTOMATON
Authors: AKTEKİN N.
Published: April 2003

The Ising models in five to seven dimensions are simulated on the Creutz cellular automaton with the three- to five-bit demons on finite-size lattices. The simulations result in overlapping curves for both the order parameter and the internal energy. However, the magnetic susceptibility and the specific heat curves converge to the limiting ones as the number of bits increases. By fitting the order parameter data within the temperature interval where the infinite lattice is approximated, 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 for the infinite lattice is obtained. For the Ising models in five to seven dimensions, they are in agreement with the Monte Carlo and the series expansion results.
INFORMATION CONTENT IN UNIFORMLY DISCRETIZED GAUSSIAN NOISE: OPTIMAL COMPRESSION RATES
Authors: ROMEO AUGUST , GAZTAÑAGA ENRIQUE , BARRIGA JOSE , ELIZALDE EMILIO
Published: April 2003

We approach the theoretical problem of compressing a signal dominated by Gaussian noise. We present expressions for the compression ratio which can be reached, under the light of Shannon's noiseless coding theorem, for a linearly quantized stochastic Gaussian signal (noise). The compression ratio decreases logarithmically with the amplitude of the frequency spectrum P(f) of the noise. Entropy values and compression rates are shown to depend on the shape of this power spectrum, given different normalizations. The cases of white noise (w.n.), fnp power-law noise (including 1/f noise), ( w.n. +1/f) noise, and piecewise ( w.n. +1/f | w.n. +1/f2) noise are discussed, while quantitative behaviors and useful approximations are provided.
COMPARATIVE STUDY OF SPANNING CLUSTER DISTRIBUTIONS IN DIFFERENT DIMENSIONS
Authors: SEN PARONGAMA
Published: April 2003

The probability distributions of the masses of the clusters spanning from top to bottom of a percolating lattice at the percolation threshold are obtained in all dimensions, from two to five. The first two cumulants and the exponents for the universal scaling functions are shown to have simple power law variations with the dimensionality. The cases where multiple spanning clusters occur are discussed separately and compared.
THREE-DIMENSIONAL ISING NUCLEATION AT LOW TEMPERATURES
Authors: STAUFFER DIETRICH
Published: April 2003

Simulations at T/Tc = 1/4 agree with classical nucleation theory if the droplets are assumed as small cubes instead of spheres.
FAST PARTICLE PAIR DETECTION ALGORITHMS FOR PARTICLE SIMULATIONS
Authors: IWAI T. , HONG C.-W. , GREIL P.
Published: April 2003

New algorithms with O(N) complexity have been developed for fast particle-pair detections in particle simulations like the discrete element method (DEM) and molecular dynamic (MD). They exhibit robustness against broad particle size distributions when compared with conventional boxing methods. Almost similar calculation speeds are achieved at particle size distributions from is mono-size to 1:10 while the linked-cell method results in calculations more than 20 times. The basic algorithm, level-boxing, uses the variable search range according to each particle. The advanced method, multi-level boxing, employs multiple cell layers to reduce the particle size discrepancy. Another method, indexed-level boxing, reduces the size of cell arrays by introducing the hash procedure to access the cell array, and is effective for sparse particle systems with a large number of particles.
ANISOTROPIC FINITE-SIZE SCALING ANALYSIS OF A THREE-DIMENSIONAL DRIVEN-DIFFUSIVE SYSTEM
Authors: LEUNG KWAN-TAI , WANG JIAN-SHENG
Published: April 2003

We study the standard three-dimensional driven diffusive system on a simple cubic lattice where particle jumping along a given lattice direction are biased by an infinitely strong field, while those along other directions follow the usual Kawasaki dynamics. Our goal is to determine which of the several existing theories for critical behavior is valid. We analyze finite-size scaling properties using a range of system shapes and sizes far exceeding previous studies. Four different analytic predictions are tested against the numerical data. Binder and Wang's prediction does not fit the data well. Among the two slightly different versions of Leung, the one including the effects of a dangerous irrelevant variable appears to be better. Recently proposed isotropic finite-size scaling is inconsistent with our data from cubic systems, where systematic deviations are found, especially in scaling at the critical temperature.
METHODS OF NUMERICAL ANALYSIS OF ONE-DIMENSIONAL TWO-BODY PROBLEM IN WHEELER-FEYNMAN ELECTRODYNAMICS
Authors: KLIMENKO S. V. , NIKITIN I. N. , URAZMETOV W. F.
Published: April 2003

Numerical methods for solutions of differential equations with deviating arguments describing one-dimensional ultra-relativistic scattering of two identical charged particles in Wheeler-Feynman electrodynamics with half-retarded/half-advanced interaction are developed. Utilization of the methods for the physical problem analysis leads to the discovery of a bifurcation of solutions and breaking of their reflectional symmetry for particles asymptotic velocity v>0.937c in their center-of-mass frame.
DENSITY PROFILE OF THE INCIPIENT INFINITE PERCOLATION CLUSTER
Authors: STAUFFER DIETRICH , AHARONY AMNON
Published: April 2003

Monte Carlo simulations show simple scaling for the number of sites in the spanning cluster at the percolation threshold as a function of distance from the border. The results for free boundary conditions represent crossover from surface to bulk fractal dimensions, and the former agrees with exact results in d=2 and d=6-∊ dimensions and with earlier simulations. We also present and explain results for bus–bar boundary conditions, with two types of connection rules. The scaling functions, which are predicted to be universal, surprisingly seem not to depend on the aspect ratios of the samples.
SIMPLE QUEUEING MODEL APPLIED TO THE CITY OF PORTLAND
Authors: SIMON PATRICE M. , ESSER JÖRG , NAGEL KAI
Published: April 2003

We use a simple traffic micro-simulation model based on queueing dynamics as introduced by Gawron [IJMPC, 9(3):393, 1998] in order to simulate traffic in Portland/Oregon. Links have a flow capacity, that is, they do not release more vehicles per second than is possible according to their capacity. This leads to queue built-up if demand exceeds capacity. Links also have a storage capacity, which means that once a link is full, vehicles that want to enter the link need to wait. This leads to queue spill-back through the network. The model is compatible with route-plan-based approaches such as TRANSIMS, where each vehicle attempts to follow its pre-computed path. Yet, both the data requirements and the computational requirements are considerably lower than for the full TRANSIMS microsimulation. Indeed, the model uses standard emme/2 network data, and runs about eight times faster than real time with more than 100 000 vehicles simultaneously in the simulation on a single Pentium-type CPU.

We derive the model's fundamental diagrams and explain it. The simulation is used to simulate traffic on the emme/2 network of the Portland (Oregon) metropolitan region (20 000 links). Demand is generated by a simplified home-to-work destination assignment which generates about half a million trips for the morning peak. Route assignment is done by iterative feedback between micro-simulation and router. An iterative solution of the route assignment for the above problem can be achieved within about half a day of computing time on a desktop workstation. We compare results with field data and with results of traditional assignment runs by the Portland Metropolitan Planning Organization.

Thus, with a model such as this one, it is possible to use a dynamic, activities-based approach to transportation simulation (such as in TRANSIMS) with affordable data and hardware. This should enable systematic research about the coupling of demand generation, route assignment, and micro-simulation output.
SOFTENING OF PHASE TRANSITION BY RANDOM DISTRIBUTION OF BIMODAL-BONDS IN THE 2D 8-STATE POTTS MODEL
Authors: YAŞAR FATIH , GÜNDÜÇ YIĞIT , ÇELIK TARIK
Published: April 2003

We investigated the influence of the distribution of bimodal bonds on phase transition in 8-state Potts model in two dimensions. We show that there is a finite size dependent threshold value of the introduced quenched randomness in the bond distribution for rounding the first-order phase transition.
SYMPLECTIC NUMERICAL METHODS IN DYNAMICS OF NONLINEAR WAVES
Authors: SHAGALOV A. G.
Published: April 2003

The symplectic integrator of the Gauss–Legendre type is tested on the nonlinear Schrödinger equation. Preservation of high integrals (up to 10 or more) and quasiperiodic motion have been detected for dynamics on both stable soliton and homoclinic manifolds, which indicate applicability of symplectic integrators for adequate simulation of integrable equation. The tested integrator is applied to the problem of long-time stability of the solitons in higher-derivative nonlinear Schrödinger equation. The slow logarithmic-type depletion of the soliton amplitude with time has been detected.
SYMBOLIC COMPUTATION OF BÄCKLUND TRANSFORMATION AND EXACT SOLUTIONS TO THE VARIANT BOUSSINESQ MODEL FOR WATER WAVES
Authors: TIAN BO
Published: April 2003

In this paper, we show how computerized symbolic computations can be used to find an auto-Bäcklund transformation and a family of exact analytical solutions to the variant Boussinesq model for water waves. Sample explicit solutions are presented, which are respectively solitonic and rational.
SIMILARITY REDUCTIONS FOR A GENERALIZED VARIABLE-COEFFICIENT KADOMTSEV–PETVIASHVILI EQUATION WITH SYMBOLIC COMPUTATION
Authors: TIAN BO
Published: April 2003

We use computerized symbolic computation to study the similarity reductions of a generalized Kadomtsev–Petviashvili (KP) equation, with its space- and time-dependent coefficients arising in plasma physics and fluid mechanics. We obtain a couple of reductions involving those coefficient functions, one of which is to the fourth Painlevé equation, while the other is to one of the second Painlevé equation, the first Painlevé equation or a Weierstrass elliptic function equation. Our results agree with the Painlevé Conjecture. The cylindrical KP equation is presented as an example, which describes nonlinear cylindrical water waves in shallow water with a weak azimuthal dependence.
ANALYSIS OF THE PHENOMENON OF SPECULATIVE TRADING IN ONE OF ITS BASIC MANIFESTATIONS: POSTAGE STAMP BUBBLES
Authors: ROEHNER B. , SORNETTE D.
Published: April 2003

We document and analyze the empirical facts concerning one of the clearest evidence of speculation in financial trading as observed in the postage collection stamp market. We unravel some of the mechanisms of speculative behavior which emphasize the role of fancy and collective behavior. In our conclusion, we propose a classification of speculative markets based on two parameters, namely the amplitude of the price peak and a second parameter that measures its "sharpness". This study is offered to anchor modeling efforts to realistic market constraints and observations.
SPEAKER NORMALIZATION IMPROVEMENT BY NEURAL NETWORK PARAMETER OPTIMIZATION
Authors: AUTIERO MICHELE , GIULIANI DIEGO , RAMPONE SALVATORE , TAGLIAFERRI ROBERTO
Published: April 2003

In this work we investigate the use of a speaker adaptation technique, for speech recognition, based on neural network spectral mapping. Different multilayer perceptron neural network architectures are analyzed in order to optimize the spectral difference reduction in acoustic data of two speakers. Experiments are carried out in a telecontrol environment, used to provide voice commands to a mobile robot, based on DTW pattern matching.
THE TEST OF THE FINITE-SIZE SCALING RELATIONS FOR THE FIVE-DIMENSIONAL ISING MODEL ON THE CREUTZ CELLULAR AUTOMATON
Authors: AKTEKIN N. , ERKOÇ Ş. , KALAY M.
Published: April 2003

The five-dimensional Ising model is simulated on the Creutz cellular automaton using the finite-size lattices with the linear dimension 4≤L≤16. The exponents in the finite-size scaling relations for the magnetic susceptibility and the order parameter at the infinite-lattice critical temperature are computed to be 2.52(7) and 1.25(11) using 6≤L≤12, respectively, which are in very good agreement with the Monte Carlo results and with the theoretical predictions of 5/2 and 5/4. The critical temperature for the infinite lattice is found to be 8.779(8) using 8≤L≤16 which is also in very good agreement with the recent precise results.
INFLUENCE OF A STRUCTURE ON SYSTEM'S DYNAMICS ON EXAMPLE OF BOOLEAN NETWORKS
Authors: KIRILLOVA O. V.
Published: April 2003

In this work, the Boolean Networks of different geometric shape and lattice organization were studied. It was revealed that not only a spatial shape but also the type of lattice are very important for definition of the structure-dynamics relation. The regular structures do not give a critical regime in the investigated cases. Hierarchy together with the irregular structure reveals characteristic features of criticality.
STUDY OF PHASE SEPARATION IN A FIRST-ORDER PHASE TRANSITION: NUCLEATION VERSUS SPINODAL DECOMPOSITION
Authors: ARKIN H. , ÇELIK T. , BERG B. A. , MEYER-ORTMANNS H.
Published: April 2003

Studies of dynamical properties of first-order phase transition for a scalar field theory indicate that the phase conversion mechanism itself depends on the strength of the first-order transition: if the transition is strongly (weakly) first-order, bubble nucleation (spinodal decomposition) are favored conversion mechanisms, respectively. These distinct scenarios are of phenomenological impact. In order to see which phase conversion mechanism takes place depending on the strength of transition, we have simulated the q=5 state Potts model in two dimensions with an external magnetic field. The transition gets weakened in its first-order as the external field increases. Our results indicate that the phase conversion mechanism changes from nucleation to spinodal decomposition.
SPECIATION FROM EVOLUTION
Authors: MCMANUS SCOTT , HUNTER D. L. , JAN NAEEM , RAY TANE , MOSELEY LEO
Published: April 2003

Evolution, based on the principles of mutation and selection, is a powerful basis for microscopic changes which can account for the evolution of a species and macroscopic speciation where there is splitting of a species into two distinct new species. We show that a single species evolves into distinct species after several generations in an unrestricted genome space.
CRITICAL CURRENT IN THE HIGH-Tc GLASS MODEL
Authors: MORGENSTERN I. , FETTES W. , HUSSLEIN T.
Published: April 2003

The high-Tc glass model can be combined with the repulsive tt'–Hubbard model as microscopic description of the striped domains found in the high-Tc materials. In this picture, the finite Hubbard clusters are the origin of the d-wave pairing. In this paper we show that the glass model can also explain the critical currents usually observed in the high-Tc materials. We use two different approaches to calculate the critical current densities of the high-Tc glass model. Both lead to a strongly anisotropic critical current. Finally we give an explanation of why we nonetheless expect a nearly perfect isotropic critical current in high-Tc superconductors.
PROBABILISTIC GENERALIZATION OF PENNA AGEING MODEL AND THE OLDEST OLD
Authors: STAUFFER D.
Published: April 2003

Using a 1995 method of Thoms et al., the traditional Penna model of biological ageing is modified such that there is no more absolute maximum life span; instead, our Monte Carlo data are similar to real demographic data collected by Thatcher et al., for rich countries.
COMPUTATIONICS AND QUANTUM ANALYSIS
Authors: SUZUKI MASUO
Published: April 2003

The purpose of the present paper is to review briefly the quantum analysis and to apply it in deriving quantum correlation identities. These give the nonlinear response of isotropic magnetic systems in the presence of a finite magnetic field. Hybrid exponential product formulas are also discussed from the point of computationics, as an application of the quantum analysis.
CLUSTER METHODS FOR ISING SYSTEMS WITH FIELDS
Authors: MACHTA J.
Published: April 2003

Efficient cluster algorithms for Ising systems with fields are described. Cluster are grown between two replicas of the system in the same field. As is the case for other successful cluster approaches, the critical point of the spin system coincides with the percolation threshold of the clusters. Applications are discussed.
COOLING RATE DEPENDENCE AND DYNAMIC HETEROGENEITY BELOW THE GLASS TRANSITION IN A LENNARD–JONES GLASS
Authors: VOLLMAYR-LEE K. , KOB W. , BINDER K. , ZIPPELIUS A.
Published: April 2003

We investigate a binary Lennard–Jones mixture with molecular dynamics simulations. We consider first a system cooled linearly in time with the cooling rate γ. By varying γ over almost four decades we study the influence of the cooling rate on the glass transition and on the resulting glass. We find for all investigated quantities a cooling rate dependence; with decreasing cooling rate the system falls out of equilibrium at decreasing temperatures, reaches lower enthalpies and obtains increasing local order. Next we study the dynamics of the melting process by investigating the most immobile and most mobile particles in the glass. We find that their spatial distribution is heterogeneous and that the immobile/mobile particles are surrounded by denser/less dense cages than an average particle.
ADVANCED DYNAMIC ALGORITHMS FOR THE DECAY OF METASTABLE PHASES IN DISCRETE SPIN MODELS: BRIDGING DISPARATE TIME SCALES
Authors: NOVOTNY M. A.
Published: April 2003

An overview of advanced dynamical algorithms capable of spanning the widely disparate time scales that govern the decay of metastable phases in discrete spin models is presented. The algorithms discussed include constrained transfer-matrix, Monte Carlo with Absorbing Markov Chains (MCAMC), and projective dynamics (PD) methods. The strengths and weaknesses of each of these algorithms are discussed, with particular emphasis on identifying the parameter regimes (system size, temperature, and field) in which each algorithm works best.
APPLICATION OF THE PROJECTED DYNAMICS METHOD TO AN ANISOTROPIC HEISENBERG MODEL
Authors: MITCHELL S. J. , NOVOTNY M. A. , MUÑOZ JOSÉ D.
Published: April 2003

The Projected Dynamics method was originally developed to study metastable decay in ferromagnetic discrete spin models. Here, we apply it to a classical, continuous Heisenberg model with anisotropic ferromagnetic interactions, which evolves under a Monte Carlo dynamic. The anisotropy is sufficiently large to allow comparison with the Ising model. We describe the Projected Dynamics method and how to apply it to this continuous-spin system. We also discuss how to extract metastable lifetimes and how to extrapolate from small systems to larger systems.
DYNAMIC DENSITY FUNCTIONAL APPROACH TO PHASE SEPARATION DYNAMICS OF POLYMER SYSTEMS
Authors: KAWAKATSU T. , DOI M. , HASEGAWA R.
Published: April 2003

Slow dynamics of complex domain structures in phase separating polymer systems is investigated with the use of the self-consistent field (SCF) dynamic density functional (DDF) technique where the free energy of the system is calculated using the path integral formalism of the polymer chain conformation. We apply this technique to micellization of block copolymers and to phase separation of polymer blends containing block copolymers as a compatibilizer. In order to study the late stage of the phase separation processes more efficiently, we adopt the so-called Ginzburg–Landau approach, where a phenomenological model free energy functional is used. Numerical results of this approach is quantitatively compared with the results of the SCF approach.
IMPROVED SPIN DYNAMICS SIMULATIONS OF MAGNETIC EXCITATIONS
Authors: LANDAU D. P. , TSAI SHAN-HO , KRECH M. , BUNKER ALEX
Published: April 2003

Using Suzuki–Trotter decompositions of exponential operators we describe new algorithms for the numerical integration of the equations of motion for classical spin systems. These techniques conserve spin length exactly and, in special cases, also conserve the energy and maintain time reversibility. We investigate integration schemes of up to eighth order and show that these new algorithms can be used with much larger time steps than a well established predictor–corrector method. These methods may lead to a substantial speedup of spin dynamics simulations, however, the choice of which order method to use is not always straightforward.
TACKLING THE MULTIPLE-MINIMA PROBLEM IN PROTEIN FOLDING BY MONTE CARLO SIMULATED ANNEALING AND GENERALIZED-ENSEMBLE ALGORITHMS
Authors: OKAMOTO YUKO
Published: April 2003

Monte Carlo simulations based on simulated annealing and multicanonical algorithm have been performed to predict the secondary and tertiary structures of oligopeptide systems. Two oligopeptides, C-peptide of ribonuclease A and the fragment BPTI(16-36) of bovine pancreatic trypsin inhibitor, were studied. Only the amino-acid sequence information was used as input and initial conformations were randomly generated. The lowest-energy conformations obtained have α-helix structure and β-sheet structure for C-peptide and BPTI(16-36), respectively, in remarkable agreement with experimental results.
STATE MEASUREMENT BY PHOTON FILTERING IN A RING CAVITY
Authors: D'ARIANO G. M. , MACCONE L. , PARIS M. G. , SACCHI M. F.
Published: April 2003

We suggest a method for measuring the photon number distribution and the density matrix of a single-mode radiation field. The setup consists of a chain of active ring cavities, each fed by a strong coherent probe and coupled to the signal through cross-Kerr phase modulation. Each cavity is set at resonance by a different Fock component of the signal, so that the detection probability at the cavities output is proportional to the signal photon statistics. The off-diagonal elements of the density matrix can be evaluated by measuring the photon statistics of a set of displaced signal states. The suggested setup allows a reliable state measurement even with low quantum efficiency at detectors.
ELECTRONIC PROPERTIES OF HETEROFULLERENES C59X (X=Si, O AND Be)
Authors: LU JING , ZHANG XINWEI , ZHAO XIANGENG
Published: April 2003

It has been found in earlier calculations that by replacing one C atom with one N atom, one electron is doped in the lowest unoccupied molecular orbital (LUMO) of C60 while by replacing with one B atom, one hole is doped in the highest occupied molecular orbital (HOMO) of C60. In this paper, we have performed discrete-variational local density functional calculations on single silicon, oxygen and beryllium-substituted heterofullerenes. No carrier is doped in the C60-derived orbitals upon Si substitution except for the reduced LUMO–HOMO gap. Two electrons are doped in the LUMO of C60 upon O substitution and instead, two holes are doped in the HOMO of C60 upon Be substitution. Ionization potentials and electron affinities can be altered dramatically by substitution and in general, C60 becomes more reactive upon substitution.
1/f NOISE IN THE "GAME OF LIFE"
Authors: ANDRECUT MIRCEA
Published: April 2003

Conway's celebrated "game of life" cellular automaton possesses computational universality. The Fourier analysis reported here shows that the power spectra of the "game of life" exhibit 1/f noise. The obtained result suggests a connection between 1/f noise and computational universality.
Cooling, Trapping and Manipulation of Neutral Atoms and Bose-Einstein Condensates by Electromagnetic Fields
Authors: Helmerson Kristian , Phillips William D.
Published: April 2003

We give a general discussion of the mechanical effects of light, and of laser cooling and trapping techniques. This is followed by a description of experiments in the manipulation of Bose-Einstein condensates with optical laser pulses.
AUTOMATED REQUIREMENTS ELICITATION: COMBINING A MODEL-DRIVEN APPROACH WITH CONCEPT REUSE
Authors: JIN Z. , BELL D. A. , WILKIE F. G. , LEAHY D. G.
Published: April 2003

Extracting pertinent and useful information from customers has long plagued the process of requirements elicitation. This paper presents a new approach to support the elicitation process. This approach combines various techniques for requirements elicitation which include model-based concept acquisition, goal-driven structured interview and concept reuse. Compared with the available approaches for requirements elicitation, the most significant feature of our approach is that it supports both the automation of interaction with customers by using domain terminology, not software terminology and the automated construction of application requirements models using model-based concept elicitation and concept reuse. The capacity of this approach comes from its rich knowledge which is clustered into several abstract levels.
VISUALIZING ANIMATION DATABASES
Authors: AKANKSHA  , HUANG Z. , PRABHAKARAN B. , RUIZ C. R.
Published: April 2003

We consider a repository of animation models and motions that can be reused to generate new animation sequences. For instance, a user can retrieve an animation of a dog kicking its leg (in air) and manipulate the result to generate a new animation where the dog is kicking a ball. In this particular example, inverse kinematics technique can be used to retarget the kicking motion of a dog to a ball. This approach of reusing models and motions to generate new animation sequences can be facilitated by operations such as querying of animation databases for required models and motions, and manipulation of the query results to meet new constraints. However, manipulation operations such as motion retargeting are quite complex in nature. Hence, there is a need for visualizing the queries on animation databases as well as the manipulation operations on the query results.

In this paper, we propose a visually interactive method for reusing motions and models, by adjusting the query results from animation databases for new situations while at the same time, keeping the desired properties of the original models and motions. Here, a user first queries for animation objects, i.e., geometric models and motions. Then, the user interactively makes new animations by visually manipulating the query results. Depending on the orders in which the GUIs (Graphical User Interfaces) are invoked and the parameters are changed, the system automatically generates a sequence of operations, a list of SQL-like syntax commands, and applies it to the query results of motions and models. With the help of visualization tools, the user can view the changes before accepting them.