bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser-produced-plasma light source development for extreme ultraviolet lithography
Authors: Komori Hiroshi , Abe Tamotsu , Suganuma Takashi , Imai Yousuke , Sugimoto Yukihiko , Someya Hiroshi , Hoshino Hideo , Soumagne Georg , Takabayashi Yuichi , Mizoguchi Hakaru , Endo Akira , Toyoda Koichi , Horiike Yasuhiro
Published: December 2003

The development status of our laser produced plasma EUV light source is reported including the xenon jet system and the 500 W laser system. Laser parameter optimization, for example, laser pulse energy, pulse width, and laser spot size, is ongoing to improve the conversion efficiency and EUV output power. A maximum conversion efficiency of 0.53% is obtained with a 50 μm diam target. The EUV output stability is analyzed based on spatial fluctuations of the Xe jet and the laser beam. In addition, a Xe ion exposure measurement has been started to investigate the collector mirror damage mechanism.
The case for diffractive optics in maskless lithography
Authors: Gil Dario , Menon Rajesh , Smith Henry I.
Published: December 2003

For photon-based maskless lithography we show that a system based on the incoherent addition of scanned, multiplexed, and on-axis focal spots from an array of diffractive-optical elements, such as binary-phase zone plates, has significant advantages over systems based on partially coherent projection of the image of a micromechanical mirror array through a large refractive or reflective lens. We show that zone-plate arrays with numerical apertures up to 0.9 can be manufactured with near-ideal performance, and used to achieve high-quality lithography of arbitrary patterns. Using a wavelength of 400 nm we demonstrate k1 factors as low as 0.32, without the use of any resolution-enhancement techniques; that sufficient contrast is achieved in dense patterns despite the presence of diffracted orders other than +1; and that a process-latitude greater than 10% is achieved for 150 nm lines and spaces. Advantages of our diffractive-optical approach include: the feasibility of wave-front engineering by using elements other than binary-phase zone plates; the simplicity of the processes needed to manufacture large arrays of high-numerical-aperture diffractive-optical elements; and the ease of wavelength scaling, with the promise of ultimately approaching the limits of the lithographic process.
Influence of oxidation temperature on Si-single electron transistor characteristics
Authors: Namatsu H. , Watanabe Y. , Yamazaki K. , Yamaguchi T. , Nagase M. , Ono Y. , Fujiwara A. , Horiguchi S.
Published: December 2003

In order to make practical single-electron transistors (SET) that can operate at room temperature, it is necessary to determine the process factors that most influence their characteristics. For that purpose, the relationship between the oxidation temperature and the electrical characteristics of SETs was examined using SETs fabricated with precise dimensions by e-beam nanolithography, because a Si nanowire must be oxidized to convert it into the small Si island and tunnel barriers required for a SET. SETs fabricated using a relatively low oxidation temperature, such as 800 °C, were found to exhibit clear Coulomb blockade oscillations at room temperature; while SETs fabricated using a temperature of 900 °C did not, even though the nanowires were about the same size. At intermediate temperatures, such as 850 °C, the characteristics were between those for 800 and 900 °C oxidation. The most probable explanation for these results is as follows: The small roughness inherent to the resist is transferred to the nanowire during etching and remains after oxidation, provided that the oxidation temperature is low enough. This results in the formation of multiple islands, which can be extremely small and which enable the room-temperature operation of a Si SET due to the quantum-mechanical size effect.
Molybdenum/pure aluminum gate bus line defect reduction for high-resolution thin film transistor liquid crystal displays
Authors: Tsujimura Takatoshi , Makita Atsuya
Published: December 2003

Defect mode analysis for pure aluminum was done to improve fabrication of very large high-resolution thin film transistor liquid crystal displays with very low gate line delay. Mouse hole defects in pure aluminum films are caused by the stress voiding due to the heating/cooling process and by vacancy diffusion. An oxygen treatment between the molybdenum and aluminum depositions is very effective in completely suppressing mouse hole formation. An additive material is also effective in suppressing mouse holes because of the reduction in grain size and the vacancy pinning. Blisters are created during heating processes and can be suppressed by using a MoTa/Mo/aluminum structure or by removal of the undercoat layer.
Study on optical intensity distribution in photocuring nanoimprint lithography
Authors: Hirai Yoshihiko , Kikuta Hisao , Sanou Toshikazu
Published: December 2003

Optical intensity distribution in photocuring nanoimprint lithography is investigated. Its dependency on pattern size, optical index, and residual thickness of the photopolymer has been numerically evaluated using the finite-difference time-domain method. The irradiated beam propagates mostly in the photopolymer, where the optical index is larger than that of the quartz mold. If the pattern size is less than around 1/4 wavelength of the irradiated beam, optical intensity in the polymer decreases because the light propagates through both the polymer and quartz molds. In addition, the index difference between mold and polymer increases diffraction into the residual layer and causes optical intensity concentration at a particular position.
Free-space-wiring fabrication in nano-space by focused-ion-beam chemical vapor deposition
Authors: Morita Takahiko , Kometani Reo , Watanabe Keiichiro , Kanda Kazuhiro , Haruyama Yuichi , Hoshino Takayuki , Kondo Kazushige , Kaito Takashi , Ichihashi Toshinari , Fujita Jun-ichi , Ishida Masahiko , Ochiai Yukinori , Tajima Tsutomu , Matsui Shinji
Published: December 2003

Focused-ion-beam chemical vapor deposition (FIB-CVD) is an excellent technology for forming three-dimensional nanostructures. Various diamond-like-carbon (DLC) free-space-wirings have been demonstrated by FIB-CVD using a computer-controlled pattern generator, which is a commercially available pattern generator for electron-beam (EB) lithography. The material composition and crystal structure of DLC free-space-wiring were studied by transmission-electron microscopy and energy-dispersive x-ray spectroscopy. As a result, it became clear that DLC free-space-wiring is amorphous carbon containing a Ga core in the wire. Furthermore, the electrical resistivity measurement of DLC free-space-wiring was carried out by two terminal electrodes. Au electrodes were fabricated by EB lithography and a lift-off process. The electrical resistivity was about 100 Ω cm at room temperature.
Monte Carlo simulation of the image formation process in portal imaging
Authors: Bissonnette Jean‐Pierre , Munro P. , Cunningham I. A.
Published: December 2003

We have written Monte Carlo programs to simulate the formation of radiological images. Our code is used to propagate a simulated x‐ray fluence through each component of an existing video‐based portal imaging system. This simulated fluence consists of a image containing both contrast‐detail patterns as well as checker patterns to assess spatial resolution of the simulated portal imager. All of the components of the portal imaging system were modeled as a cascade of eight linear stages. Using this code, one can assess the visual impact of changing components in the imaging chain by changing the appropriate probability density function. Virtual experiments were performed to assess the visual impact of replacing the lens and TV camera by an amorphous silicon array, and the effect of scattered radiation on portal images.
Carotid geometry reconstruction: a comparison between MRI and ultrasound
Authors: Glor F. P. , Ariff B. , Crowe L. A. , Hughes A. D. , Cheong P. L. , Thom S. A. McG. , Verdonck P. R. , Firmin D. N. , Barratt D. C. , Xu X. Y.
Published: December 2003

Image‐based Computational Fluid Dynamics (CFD) has become a popular tool for the prediction of in vivo flow profiles and hemodynamic wall parameters. Currently, Magnetic Resonance Imaging (MRI) is most widely used for in vivo geometry acquisition. For superficial arteries such as the carotids and the femoral artery, three‐dimensional (3‐D) extravascular ultrasound (3‐DUS) could be a cost‐effective alternative to MRI. In this study, nine healthy subjects were scanned both with MRI and 3‐DUS. The reconstructed carotid artery geometries for each subject were compared by evaluating cross‐sectional areas, centerlines, and carotid nonplanarity. Lumen areas agreed very well between the two different acquisition techniques, whereas centerlines and nonplanarity parameters showed measurable disagreement, possibly due to the different neck and head positions adopted for 3‐DUS versus MRI. With the current level of agreement achieved, 3‐DUS has the potential to become an inexpensive and fast alternative to MRI for image‐based CFD modeling of superficial arteries.
Longitudinal Magnification Drawing Mistake
Authors: Rabal Héctor , Cap Nelly , Trivi Marcelo
Published: December 2003

Lateral magnification in image formation by positive lenses, mirrors, and dioptrics is usually appropriately developed in most optics textbooks.1–9 However, the image of a three-dimensional object occupies a three-dimensional region of space. The optical system affects both the transverse and the longitudinal dimensions of the object and, in general, does it in different ways. The magnification in the direction of the optical axis (the longitudinal magnification) is seldom treated. In several texts, the concept of longitudinal magnification is not even considered. Symmetrical objects (such as arrows) are used and their images appear laterally inverted. It is not shown how a longitudinally nonsymmetric object is imaged. One of the few books where this subject is well treated is in the textbook by Hecht.10 We have repeatedly verified in our classes that there is some confusion related to this subject. Students tend to believe that the image is longitudinally symmetric with respect to the lens optic center. Some prestigious texts commit the same mistake. In addition, a very nice optics book,11 a catalogue of optical hardware,12 a worldwide scientific magazine,13 a paper in an optics journal,14 and a Spanish encyclopedia,15 for example, have also been found to contain this error in drawing the image of a three-dimensional object formed by a positive lens. In this paper we suggest that the teaching of longitudinal magnification should be done with some care and we include a figure showing a properly drawn image.
Demonstrating Newtonian Physics on the Internet
Authors: Ballester Jorge L. , Pheatt Charles B.
Published: December 2003

Experimentation is accepted as an integral part of introductory physics courses. Exposing distance-learning students to physics experimentation remains problematic. One solution is to distribute inexpensive hands-on materials, as described by McAlexander.1 Another solution could be to exploit the interactivity provided by the Internet. Java applets, such as Physlets,2 are illustrative, but are not intended to provide the perspective and uncertainty of actual experiments. Nevertheless, an apparatus that is remotely controlled, via the Internet, could provide access to an experiment that may be utilized by students. In this article, we describe a physics apparatus and associated website that allow students to conduct real online physics experiments by using only a web browser.
The Bohr Staircase
Authors: Pasachoff Jay M.
Published: December 2003

The attempt to bring students to critical thinking about topics in contemporary astronomy is a goal shared by many teachers. Since the rise of astrophysics in the early 20th century, spectroscopy has been the defining technique. Various techniques have been tried to give students a concrete understanding of emission lines and absorption lines in the hydrogen spectrum.1 Spectroscopy of hydrogen plays an important part of most textbooks in elementary astronomy.2 After years of jumping off lecture-room steps and trying (but never succeeding) in hovering between stair levels, I still find too many students drawing equally spaced hydrogen energy levels on exams. I thus arranged for carpenters to build a five-step staircase with the spacing matching that of the actual hydrogen energy levels. I can now use the staircase to demonstrate the Bohr atom3 in a memorable manner. “Bohr staircase” is therefore a suitable name for it. If a teacher wants to stress the visible spectrum rather than the energy levels, “Balmer staircase” is an alternate name.
A Project-Based Approach: Students Describe the Physics in Movies
Authors: Daley Ben
Published: December 2003

Ted Sizer, founder of the Coalition of Essential Schools, calls for teachers designing a curriculum to begin with the end in mind; that is, determine your goals and only then design appropriate assignments and assessments that guide students toward these goals. Sizer argues that students should be tested via public “exhibitions” that drive the curriculum and set clear standards for students about what is expected of them.2 This paper describes an exhibition in which students analyze the physics of movies.
Dual Activation of the
Drosophila
Toll Pathway by Two Pattern Recognition Receptors
Authors: Gobert Vanessa , Gottar Marie , Matskevich Alexey A. , Rutschmann Sophie , Royet Julien , Belvin Marcia , Hoffmann Jules A. , Ferrandon Dominique
Published: December 2003

The
Toll-
dependent defense against Gram-positive bacterial infections in
Drosophila
is mediated through the peptidoglycan recognition protein SA (PGRP-SA). A mutation termed
osiris
disrupts the
Gram-negative binding protein 1
(
GNBP1
) gene and leads to compromised survival of mutant flies after Gram-positive infections, but not after fungal or Gram-negative bacterial challenge. Our results demonstrate that GNBP1 and PGRP-SA can jointly activate the Toll pathway. The potential for a combination of distinct proteins to mediate detection of infectious nonself in the fly will refine the concept of pattern recognition in insects.
A
C. elegans
CLIC-like Protein Required for Intracellular Tube Formation and Maintenance
Authors: Berry Katherine L. , Bülow Hannes E. , Hall David H. , Hobert Oliver
Published: December 2003

The
Caenorhabditis elegans
excretory canal is composed of a single elongated and branched cell that is tunneled by an inner lumen of apical character. Loss of the
exc-4
gene causes a cystic enlargement of this intracellular tube.
exc-4
encodes a member of the chloride intracellular channel (CLIC) family of proteins. EXC-4 protein localizes to various tubular membranes in distinct cell types, including the lumenal membrane of the excretory tubes. A conserved 55–amino acid domain enables EXC-4 translocation from the cytosol to the lumenal membrane. The tubular architecture of this membrane requires EXC-4 for both its formation and maintenance.
Adaptation Limits Diversification of Experimental Bacterial Populations
Authors: Buckling Angus , Wills Matthew A. , Colegrave Nick
Published: December 2003

Adaptation to a specific niche theoretically constrains a population's ability to subsequently diversify into other niches. We tested this theory using the bacterium
Pseudomonas fluorescens
, which diversifies into niche specialists when propagated in laboratory microcosms. Numerically dominant genotypes were allowed to diversify in isolation. As predicted, populations increased in fitness through time but showed a greatly decreased ability to diversify. Subsequent experiments demonstrated that niche generalists and reductions in intrinsic evolvability were not responsible for our data. These results show that niche specialization may come with a cost of reduced potential to diversify.
Seeking Simultaneity
Authors: Wise M. Norton
Published: December 2003

Einstein's Clocks, Poincaré's Maps
Empires of Time. Peter Galison. Norton, New York, 2003. 389 pp. $23.95, C$36. ISBN 0-393-02001-0. Sceptre, London. £16.99. ISBN 0-340-79447-X.

Rather than another history of relativity, Galison offers an accessible account of the early 20th-century convergence of physics, philosophy, and technology on the meaning of simultaneity.
Genome-Wide Survey of Human Alternative Pre-mRNA Splicing with Exon Junction Microarrays
Authors: Johnson Jason M. , Castle John , Garrett-Engele Philip , Kan Zhengyan , Loerch Patrick M. , Armour Christopher D. , Santos Ralph , Schadt Eric E. , Stoughton Roland , Shoemaker Daniel D.
Published: December 2003

Alternative pre–messenger RNA (pre-mRNA) splicing plays important roles in development, physiology, and disease, and more than half of human genes are alternatively spliced. To understand the biological roles and regulation of alternative splicing across different tissues and stages of development, systematic methods are needed. Here, we demonstrate the use of microarrays to monitor splicing at every exon-exon junction in more than 10,000 multi-exon human genes in 52 tissues and cell lines. These genome-wide data provide experimental evidence and tissue distributions for thousands of known and novel alternative splicing events. Adding to previous studies, the results indicate that at least 74% of human multi-exon genes are alternatively spliced.
Pseudo-Random Unitary Operators for Quantum Information Processing
Authors: Emerson Joseph , Weinstein Yaakov S. , Saraceno Marcos , Lloyd Seth , Cory David G.
Published: December 2003

In close analogy to the fundamental role of random numbers in classical information theory, random operators are a basic component of quantum information theory. Unfortunately, the implementation of random unitary operators on a quantum processor is exponentially hard. Here we introduce a method for generating pseudo-random unitary operators that can reproduce those statistical properties of random unitary operators most relevant to quantum information tasks. This method requires exponentially fewer resources, and hence enables the practical application of random unitary operators in quantum communication and information processing protocols. Using a nuclear magnetic resonance quantum processor, we were able to realize pseudorandom unitary operators that reproduce the expected random distribution of matrix elements.
Observation of Two Distinct Superconducting Phases in CeCu
2
Si
2
Authors: Yuan H. Q. , Grosche F. M. , Deppe M. , Geibel C. , Sparn G. , Steglich F.
Published: December 2003

We report the presence of two disconnected superconducting domes in the pressure-temperature phase diagram of partially germanium-substituted CeCu
2
Si
2
. The lower density superconducting dome lies on the threshold of antiferromagnetic order, indicating magnetically mediated pairing, whereas the higher density superconducting regime straddles a weakly first-order volume collapse, suggesting a pairing interaction based on spatially extended density fluctuations. Two distinct pairing mechanisms thus appear to operate in the single, wide, superconducting range of stoichiometric CeCu
2
Si
2
, both of which might apply more generally to other classes of correlated electron systems.
Biomolecular Interactions at Phospholipid-Decorated Surfaces of Liquid Crystals
Authors: Brake Jeffrey M. , Daschner Maren K. , Luk Yan-Yeung , Abbott Nicholas L.
Published: December 2003

The spontaneous assembly of phospholipids at planar interfaces between thermotropic liquid crystals and aqueous phases gives rise to patterned orientations of the liquid crystals that reflect the spatial and temporal organization of the phospholipids. Strong and weak specific-binding events involving proteins at these interfaces drive the reorganization of the phospholipids and trigger orientational transitions in the liquid crystals. Because these interfaces are fluid, processes involving the lateral organization of proteins (such as the formation of protein- and phospholipid-rich domains) are also readily imaged by the orientational response of the liquid crystal, as are stereospecific enzymatic events. These results provide principles for label-free monitoring of aqueous streams for molecular and biomolecular species without the need for complex instrumentation.
EDIT-DISTANCE OF WEIGHTED AUTOMATA: GENERAL DEFINITIONS AND ALGORITHMS
Authors: MOHRI MEHRYAR
Published: December 2003

The problem of computing the similarity between two sequences arises in many areas such as computational biology and natural language processing. A common measure of the similarity of two strings is their edit-distance, that is the minimal cost of a series of symbol insertions, deletions, or substitutions transforming one string into the other. In several applications such as speech recognition or computational biology, the objects to compare are distributions over strings, i.e., sets of strings representing a range of alternative hypotheses with their associated weights or probabilities. We define the edit-distance of two distributions over strings and present algorithms for computing it when these distributions are given by automata. In the particular case where two sets of strings are given by unweighted automata, their edit-distance can be computed using the general algorithm of composition of weighted transducers combined with a single-source shortest-paths algorithm. In the general case, we show that general weighted automata algorithms over the appropriate semirings can be used to compute the edit-distance of two weighted automata exactly. These include classical algorithms such as the composition and ∊-removal of weighted transducers and a new and simple synchronization algorithm for weighted transducers which, combined with ∊-removal, can be used to normalize weighted transducers with bounded delays. Our algorithm for computing the edit-distance of weighted automata can be used to improve the word accuracy of automatic speech recognition systems. It can also be extended to provide an edit-distance automaton useful for re-scoring and other post-processing purposes in the context of large-vocabulary speech recognition.
FINITELY SUBSEQUENTIAL TRANSDUCERS
Authors: ALLAUZEN CYRIL , MOHRI MEHRYAR
Published: December 2003

Finitely subsequential transducers are efficient finite-state transducers with a finite number of final outputs and are used in a variety of applications. Not all transducers admit equivalent finitely subsequential transducers however. We briefly describe an existing generalized determinization algorithm for finitely subsequential transducers and give the first characterization of finitely subsequentiable transducers, transducers that admit equivalent finitely subsequential transducers. Our characterization shows the existence of an efficient algorithm for testing finite subsequentiability. We have fully implemented the generalized determinization algorithm and the algorithm for testing finite subsequentiability. We report experimental results showing that these algorithms are practical in large-vocabulary speech recognition applications. The theoretical formulation of our results is the equivalence of the following three properties for finite-state transducers: determinizability in the sense of the generalized algorithm, finite subsequentiability, and the twins property.
A FORMAL STUDY OF PRACTICAL REGULAR EXPRESSIONS
Authors: CÂMPEANU CEZAR , SALOMAA KAI , YU SHENG
Published: December 2003

Regular expressions are used in many practical applications. Practical regular expressions are commonly called "regex". It is known that regex are different from regular expressions. In this paper, we give regex a formal treatment. We make a distinction between regex and extended regex; while regex represent regular languages, extended regex represent a family of languages larger than regular languages. We prove a pumping lemma for the languages expressed by extended regex. We show that the languages represented by extended regex are incomparable with context-free languages and a proper subset of context-sensitive languages. Other properties of the languages represented by extended regex are also studied.
SIMULATION OF FEEDBACK-FREE CIRCUITS IN THE ALGEBRA OF TRANSIENTS
Authors: GHEORGHIU MIHAELA , BRZOZOWSKI JANUSZ
Published: December 2003

An efficient simulation algorithm using an algebra of transients for gate circuits was proposed by Brzozowski and Ésik. This algorithm seems capable of predicting all the signal changes that can occur in a circuit under worst-case delay conditions. We verify this claim by comparing simulation with binary analysis. For any feedback-free circuit consisting of one- and two-input gates, we prove that all signal changes predicted by simulation occur in binary analysis, provided that wire delays are taken into account. Two types of finite automata play an important role in our proof.
VIRTUAL OPERATIONS ON VIRTUAL NETWORKS: THE PRIORITY UNION
Authors: GUINGNE FRANCK , NICART FLORENT , CHAMPARNAUD JEAN-MARC , KARTTUNEN LAURI , GAÁL TAMÁS , KEMPE ANDRÉ
Published: December 2003

Finite state networks can represent dictionaries and lexical relations. Traditional finite-state operations like composition can produce huge networks with prohibitive computation space and time. For a subset of finite state operations, these drawbacks can be avoided by using virtual networks, which rely on structures that are partially built on demand. This paper addresses the implementation of virtual network operations in xfst (XEROX Finite State Technology software). The example of "priority union", which is particularly useful in NLP, is developed.
A GENERAL PRAM SIMULATION SCHEME FOR CLUSTERED MACHINES
Authors: FANTOZZI CARLO , PIETRACAPRINA ANDREA , PUCCI GEPPINO
Published: December 2003

We present a general deterministic scheme to implement a shared memory abstraction on any distributed-memory machine which exhibits a clustered structure. More specifically, we develop a memory distribution strategy and an access protocol for the Decomposable BSP (D-BSP), a generic machine model whose bandwidth/latency parameters can be instantiated to closely reflect the characteristics of machines that admit a hierarchical decomposition into independent clusters. Our scheme achieves provably optimal slowdown for those machines where delays due to latency dominate over those due to bandwidth limitations. For machines where this is not the case, the slowdown is a mere logarithmic factor away from the natural bandwidth-based lower bound.
DOUBLE HASHING WITH MULTIPLE PASSBITS
Authors: MARTINI PAUL M. , BURKHARD WALTER A.
Published: December 2003

We present a novel extension to passbits providing significant reduction to unsuccessful search lengths for open addressing collision resolution hashing. Both the experimental and analytical results presented demonstrate the dramatic reductions possible. This method does not restrict the hashing table configuration parameters and utilizes very little additional storage space per bucket. The runtime performance for insertion is essentially the same as for ordinary open addressing with passbits; the successful search lengths remain the same as for open addressing without passbits. For any given loading factor, the unsuccessful search length can be made to be arbitrarily close to one bucket access.
THE KAPPA FUNCTION
Authors: KANEKO MASANOBU , YOSHIDA MASAAKI
Published: December 2003

The Kappa function is introduced as the function κ satisfying J(κ(τ)) = λ(τ), where J and λ are the elliptic modular functions. A Fourier expansion of κ is studied.
BORDER-COLLISION BIFURCATIONS IN ONE-DIMENSIONAL DISCONTINUOUS MAPS
Authors: JAIN PARAG , BANERJEE SOUMITRO
Published: December 2003

We present a classification of border-collision bifurcations in one-dimensional discontinuous maps depending on the parameters of the piecewise linear approximation in the neighborhood of the point of discontinuity. For each range of parameter values we derive the condition of existence and stability of various periodic orbits and of chaos. This knowledge will help in understanding the bifurcation phenomena in a large number of practical systems which can be modeled by discontinuous maps in discrete domain.
SMOOTH SYMMETRIC AND LORENZ MODELS FOR UNIMODAL MAPS
Authors: LI MING-CHIA , MALKIN MIKHAIL
Published: December 2003

For a given unimodal map F:I→I on the interval I, we consider symmetric unimodal maps (models) so that they are conjugate to F. The question motivated by [Gambaudo & Tresser, 1992] is the following: whether it is possible for symmetric model to preserve smoothness of the initial map F? We construct a symmetric model which is proved to be as smooth as F provided F has a nonflat turning point with sufficient "reserve of local evenness" at the turning point (in terms of one-sided higher derivatives at the turning point, see Definition 2.4 and Theorem 2.7). We also consider from different points of view the relationship between dynamical and ergodic properties of unimodal maps and of symmetric Lorenz maps. In particular, we present a one-to-one correspondence preserving the measure theoretic entropy, between the set of invariant measures of a symmetric unimodal map F and the set of symmetric invariant measures of the Lorenz model of F (Theorem 3.5), where by Lorenz model of F we mean the discontinuous map obtained from F by reversing its decreasing branch. Finally we extend for nonsymmetric unimodal maps, the result of Gambaudo and Tresser [1992] on Ck structural instability of the maps whose rotation interval has irrational end point (answering a question from [Gambaudo & Tresser, 1992]).
PSEUDO-RANDOMNESS OF ROUND-OFF ERRORS IN DISCRETIZED LINEAR MAPS ON THE PLANE
Authors: VIVALDI FRANCO , VLADIMIROV IGOR
Published: December 2003

We analyze the sequences of round-off errors of the orbits of a discretized planar rotation, from a probabilistic angle. It was shown [Bosio & Vivaldi, 2000] that for a dense set of parameters, the discretized map can be embedded into an expanding p-adic dynamical system, which serves as a source of deterministic randomness. For each parameter value, these systems can generate infinitely many distinct pseudo-random sequences over a finite alphabet, whose average period is conjectured to grow exponentially with the bit-length of the initial condition (the seed). We study some properties of these symbolic sequences, deriving a central limit theorem for the deviations between round-off and exact orbits, and obtain bounds concerning repetitions of words. We also explore some asymptotic problems computationally, verifying, among other things, that the occurrence of words of a given length is consistent with that of an abstract Bernoulli sequence.
ACTION AND PERIOD OF HOMOCLINIC AND PERIODIC ORBITS FOR THE UNFOLDING OF A SADDLE-CENTER BIFURCATION
Authors: DIMINNIE DAVID C. , HABERMAN RICHARD
Published: December 2003

At a saddle-center bifurcation for Hamiltonian systems, the homoclinic orbit is cusp shaped at the nonlinear nonhyperbolic saddle point. Near but before the bifurcation, orbits are periodic corresponding to the unfolding of the homoclinic orbit, while after the bifurcation a double homoclinic orbit is formed with a local and global branch. The saddle-center bifurcation is dynamically unfolded due to a slowly varying potential. Near the unfolding of the homoclinic orbit, the period and action are analyzed. Asymptotic expansions for the action, period and dissipation are obtained in an overlap region near the homoclinic orbit of the saddle-center bifurcation. In addition, the unfoldings of the action and dissipation functions associated with zero energy orbits (periodic and homoclinic) near the saddle-center bifurcation are determined using the method of matched asymptotic expansions for integrals.
BIFURCATIONS IN NUMERICAL METHODS FOR VOLTERRA INTEGRO-DIFFERENTIAL EQUATIONS
Authors: EDWARDS JOHN T. , FORD NEVILLE J. , ROBERTS JASON A.
Published: December 2003

We are interested in finding approximate solutions to parameter-dependent Volterra integro-differential equations over long time intervals using numerical schemes. This paper concentrates on changes in qualitative behavior (bifurcations) in the solutions and extends the work of Brunner and Lambert and Matthys (who considered only changes in stability behavior) to consider other bifurcations. We begin by considering a one-parameter equation with fading memory separable convolution kernel: we give an analytical discussion of bifurcations in this case and provide details of the behavior of numerical schemes. We extend our analysis to consider an equation with two-parameter fading memory convolution kernel and show the relationship to the classical test equation studied by the earlier authors. We draw attention to the fact that known stability results may not provide a reliable framework for choice of numerical scheme when other changes in qualitative behavior are also of interest. We give bifurcation plots for a variety of methods and show how, for known values of the parameters, stepsizes h>0 may be chosen to preserve the correct qualitative behavior in the numerical solution of the Volterra integro-differential equation.
PHASE CORRELATION AND CLUSTERING OF A NEAREST NEIGHBOR COUPLED OSCILLATORS SYSTEM
Authors: EL-NASHAR HASSAN F.
Published: December 2003

We investigated the phases in a system of nearest neighbor coupled oscillators before complete synchronization in frequency occurs. We found that when oscillators under the influence of coupling form a cluster of the same time-average frequency, their phases start to correlate. An order parameter, which measures this correlation, starts to grow at this stage until it reaches maximum. This means that a time-average phase locked state is reached between the oscillators inside the cluster of the same time-average frequency. With this strength the cluster attracts individual oscillators or a cluster to join in. We also observe that clustering in averaged frequencies orders the phases of the oscillators. This behavior is found at all the transition points studied.
OSCILLATIONS IN AN EXCITABLE SYSTEM WITH TIME-DELAYS
Authors: BURIĆ N. , VASOVIĆ N.
Published: December 2003

Transition from excitability to asymptotic periodicity in an excitable system, modeled by the FitzHugh–Nagumo equations, with multiple time-delays, is analyzed. It is demonstrated that, for intermediate time-lags, the system has two coexisting attractors, a hyperbolic stable fixed point and a stable limit cycle. The fixed point is destabilized via subcritical Hopf bifurcation for much larger values of the time-lags.
SEMISTABLE LIMIT CYCLES THAT BIFURCATE FROM CENTERS
Authors: GIACOMINI HECTOR , VIANO MIREILLE , LLIBRE JAUME
Published: December 2003

Suppose that the differential system [Formula: see text] has a center at the origin for ε=0, where P0, Q0, aij and bij are analytic functions in their variables, such that aij(0)=bij(0)=0. We present an analytic method to compute the semistable limit cycles which bifurcate from the periodic orbits of the analytic center, up to an arbitrary order in the perturbation parameter ε. We also provide an algorithm for the computation of the saddle–node bifurcation hypersurface of limit cycles in the parameter space {aij,bij}1≤i,j≤m. As an example, we apply the method to compute, first, the anal ytic expression of the unique semistable limit cycle of the Liénard system [Formula: see text] and second, an approximation of the saddle-node bifurcation surface of limit cycles in the parameter space (a1, a3, a5). Both computations are valid for ε sufficiently small.
CHAOTIC STATIONARY SOLUTIONS OF CELLULAR NEURAL NETWORKS
Authors: CHEN FANG-YUE , LIU ZENG-RONG
Published: December 2003

This study describes the chaotic stationary solutions of one-dimensional Cellular Neural Networks (CNN) without inputs with a specific term by applying the iteration map method. Under perfectly determined specific parameters, the map which corresponds to the stationary solution of CNN is two-dimensional and has a hyperbolic invariant Cantor set on which it is topologically conjugate to a two-sided shift of symbols space. The used main tool is the Conley–Moser conditions.
TESSELLATIONS WITH SYMMETRIES OF THE TRIANGLE GROUPS FROM DYNAMICS
Authors: CHUNG K. W. , WANG B. N.
Published: December 2003

A new and fast algorithm is presented in this paper for the automatic generation of aesthetic patterns with symmetries of the triangle groups T(p, q, r) by means of dynamical systems. Equivariant mappings with such symmetries are constructed. A modified convergence time scheme is described, which reflects the rate of convergence of various orbits and, at the same time, enhances the artistic appeal of generated images. Symmetrical chaotic attractors are generated by using a random iteration scheme. This method can be used to create a great variety of exotic symmetrical patterns.
MAKING A DISCRETE DYNAMICAL SYSTEM CHAOTIC: THEORETICAL RESULTS AND NUMERICAL SIMULATIONS
Authors: LAI DEJIAN , CHEN GUANRONG
Published: December 2003

In this paper, we study state-feedback controller design for controlling the Lyapunov exponents of an n-dimensional dynamical system. We examine some theoretical results and perform numerical simulations for systems with and without noise influence. The controlled Lyapunov exponents are asymptotically normally distributed if the system has noisy inputs. Computer simulations on finite samples are all consistent with the theoretical results.
ON CHAOTIFICATION OF DISCRETE SYSTEMS
Authors: ZHENG YONGAI , CHEN GUANRONG , LIU ZENGRONG
Published: December 2003

In this paper, the problem of making a nonlinear system chaotic by using state-feedback control is studied. The feedback controller uses a simple sine function of the system state, but only one component in each dimension. It is proved, by using the anti-integrable limit method, that the designed control system generates chaos in the sense of Devaney. In fact, the controlled system so designed is a perturbation of the original system, which turns out to be a simple Bernoulli shift.
A MODEL-BASED SCHEME FOR ANTICONTROL OF SOME CHAOTIC SYSTEMS
Authors: MORGÜL ÖMER
Published: December 2003

We consider a model-based approach for the anticontrol of some continuous time systems. We assume the existence of a chaotic model in an appropriate form. By using a suitable input, we match the dynamics of the controlled system and the chaotic model. We show that controllable systems can be chaotified with the proposed method. We give a procedure to generate such chaotic models. We also apply an observer-based synchronization scheme to compute the required input.
APPLYING RESONANT PARAMETRIC PERTURBATION TO CONTROL CHAOS IN THE BUCK DC/DC CONVERTER WITH PHASE SHIFT AND FREQUENCY MISMATCH CONSIDERATIONS
Authors: ZHOU YUFEI , TSE CHI K. , QIU SHUI-SHENG , LAU FRANCIS C. M.
Published: December 2003

The buck converter has been known to exhibit chaotic behavior in a wide parameter range. In this paper, the resonant parametric perturbation method is applied to control chaos in a voltage-mode controlled buck converter. In particular, the effects of phase shift and frequency mismatch in the perturbing signal are studied. It is shown that the control power can be significantly reduced if the perturbation is applied with an appropriate phase shift. Moreover, when frequency mismatch is inevitable, intermittent chaos occurs, but effective control can still be accomplished at the expense of raising the control power. Analysis, simulations and experimental measurements are presented to provide theoretical and practical evidences for the proposed control method.
MODELING COMPLEX DYNAMICS VIA EXTENDED PWL-BASED CNNs
Authors: FORTUNA LUIGI , RIZZO A. , XIBILIA M. G.
Published: December 2003

In this paper a new strategy is proposed in order to extend the class of complex and chaotic dynamics which can be generated by a State-Controlled CNN (SC-CNN). It is shown that, with slight modifications to the original paradigm, it is possible to represent a wide class of nonlinearities by using only piecewise linear (PWL) nonlinearities as output functions of the CNN. The adopted circuitry is presented, together with several examples concerning the emulation of the Rässler and Lorenz chaotic systems, and the Partial Differential Equations (PDE) governing the complex phenomena of solitons (Korteweg–de Vries PDE) and the activator–inhibitor reaction for the formation of patterns in the sea shells (Meinhardt–Gierer PDE). The results achieved enforce the role of SC-CNNs as universal paradigm for the generation of nonlinear, complex dynamics.
NUMERICAL SOLUTIONS OF A VECTOR GINZBURG–LANDAU EQUATION WITH A TRIPLE-WELL POTENTIAL
Authors: NEUBERGER JOHN M. , RICE DENNIS R. , SWIFT JAMES W.
Published: December 2003

We numerically compute solutions to the vector Ginzburg–Landau equation with a triple-well potential. We use the Galerkin Newton Gradient Algorithm of Neuberger and Swift and bifurcation techniques to find solutions. With a small parameter, we find a Morse index 2 triple junction solution. This is the solution for which Flores, Padilla and Tonegawa gave an existence proof. We classify all of the solutions guaranteed to exist by the Equivariant Branching Lemma at the first bifurcation points of the trivial solutions. Guided by the symmetry analysis, we numerically compute the solution branches.
3D VECTOR POISSON-LIKE PROBLEM WITH A TRIPLET OF INTRINSIC SCALAR BOUNDARY CONDITIONS
Authors: ZHU JIANG , GUERMOND JEAN-LUC , LOULA ABIMAEL F. D. , QUARTAPELLE LUIGI
Published: December 2003

In this work, we consider the three-dimensional vector Poisson-like equation supplemented by a nonstandard set of three scalar boundary conditions consisting of the simultaneous specification of the divergence of the unknown, its normal component, and the normal component of its curl on the entire boundary. A weak formulation of this elliptic boundary value problem is proposed. Existence and uniqueness of a solution are established under two compatibility conditions. An uncoupled solution algorithm is introduced together with its finite element approximation. The corresponding error analysis is performed.
SINGULAR INTEGRO-DIFFERENTIAL EQUATIONS OF PARABOLIC TYPE AND INVERSE PROBLEMS
Authors: FAVINI A. , LORENZI A.
Published: December 2003

We prove a global existence and uniqueness result for the recovery of unknown scalar kernels in linear singular first-order integro-differential initial-boundary value problems in Banach spaces. To this end use is made of suitable weighted Lp-spaces. Finally, we give a few applications to explicit singular partial integro-differential equations of parabolic type.
ON A DIFFUSIVELY CORRECTED KINEMATIC-WAVE TRAFFIC FLOW MODEL WITH CHANGING ROAD SURFACE CONDITIONS
Authors: BÜRGER R. , KARLSEN K. H.
Published: December 2003

The well-known Lighthill–Whitham–Richards kinematic traffic flow model for unidirectional flow on a single-lane highway is extended to include both abruptly changing road surface conditions and drivers' reaction time and anticipation length. The result is a strongly degenerate convection–diffusion equation, where the diffusion term, accounting for the drivers' behavior, is effective only where the local car density exceeds a critical value, and the convective flux function depends discontinuously on the location. It is shown that the validity of the proposed traffic model is supported by a recent mathematical well-posedness (existence and uniqueness) theory for quasilinear degenerate parabolic convection–diffusion equations with discontinuous coefficients.20,22 This theory includes a convergence proof for a monotone finite-difference scheme, which is used herein to simulate the traffic flow model for a variety of situations.
OPTIMAL CONTROL AND SHAPE OPTIMIZATION OF AORTO-CORONARIC BYPASS ANASTOMOSES
Authors: QUARTERONI ALFIO , ROZZA GIANLUIGI
Published: December 2003

In this paper we present a new approach in the study of Aorto–Coronaric bypass anastomoses configurations. The theory of optimal control based on adjoint formulation is applied in order to optimize the shape of the zone of the incoming branch of the bypass (the toe) into the coronary. The aim is to provide design indications in the perspective of future development for prosthetic bypasses. With a reduced model based on Stokes equations and a vorticity functional in the down field zone of bypass, a Taylor-like patch is found. A feedback procedure with Navier–Stokes fluid model is proposed based on the analysis of wall shear stress and its related indexes such as OSI.
THE TOPOLOGICAL DERIVATIVE FOR THE POISSON'S PROBLEM
Authors: FEIJÓO RAÚL A. , NOVOTNY ANTONIO A. , TAROCO EDGARDO , PADRA CLAUDIO
Published: December 2003

The Topological Derivative has been recognized as a powerful tool in obtaining the optimal topology of several engineering problems. This derivative provides the sensitivity of a problem when a small hole is created at each point of the domain under consideration. In the present work the Topological Derivative for Poisson's problem is calculated using two different approaches: the Domain Truncation Method and a new method based on Shape Sensitivity Analysis concepts. By comparing both approaches it will be shown that the novel approach, which we call Topological-Shape Sensitivity Method, leads to a simpler and more general methodology. To point out the general applicability of this new methodology, the most general set of boundary conditions for Poisson's problem, Dirichlet, Neumann (both homogeneous and nonhomogeneous) and Robin boundary conditions, is considered. Finally, a comparative analysis of these two methodologies will also show that the Topological-Shape Sensitivity Method has an additional advantage of being easily extended to other types of problems.
REFINED GEOMETRIC Lp HARDY INEQUALITIES
Authors: BARBATIS G. , FILIPPAS S. , TERTIKAS A.
Published: December 2003

For a bounded convex domain Ω in RN we prove refined Hardy inequalities that involve the Hardy potential corresponding to the distance to the boundary of Ω, the volume of Ω, as well as a finite number of sharp logarithmic corrections. We also discuss the best constant of these inequalities.
STEIN FILLINGS OF LENS SPACES
Authors: HIND R.
Published: December 2003

We describe a foliation by finite energy holomorphic curves of some symplectic manifolds which are constructed from Stein manifolds with Lens space boundaries. One application is that all such Stein manifolds bounded by the same contact Lens space are equivalent up to Stein homotopy.
PROFILE OF SOLUTIONS WITH SHARP LAYERS TO SOME SINGULARLY PERTURBED QUASILINEAR DIRICHLET PROBLEMS
Authors: GUO ZONGMING , WEBB J. R. L.
Published: December 2003

The singularly perturbed problem for the p-Laplacian [Formula: see text] is studied in a convex bounded domain Ω containing 0 when p > 2, f(0) = 0 and f has precisely 3 positive zeros. There exist a small solution [Formula: see text] and a large solution [Formula: see text] when ε is sufficiently small. By using the mountain pass lemma we show there is an intermediate positive solution uε and we study the structure of this solution.
THE ROGERS–RAMANUJAN RECURSION AND INTERTWINING OPERATORS
Authors: CAPPARELLI S. , LEPOWSKY J. , MILAS A.
Published: December 2003

We use vertex operator algebras and intertwining operators to study certain substructures of standard [Formula: see text]-modules, allowing us to conceptually obtain the classical Rogers–Ramanujan recursion. As a consequence we recover Feigin–Stoyanovsky's character formulas for the principal subspaces of the level 1 standard [Formula: see text]-modules.
GLOBAL DEFORMATIONS OF THE WITT ALGEBRA OF KRICHEVER–NOVIKOV TYPE
Authors: FIALOWSKI ALICE , SCHLICHENMAIER MARTIN
Published: December 2003

By considering non-trivial global deformations of the Witt (and the Virasoro) algebra given by geometric constructions it is shown that, despite their infinitesimal and formal rigidity, they are globally not rigid. This shows the need of a clear indication of the type of deformations considered. The families appearing are constructed as families of algebras of Krichever–Novikov type. They show up in a natural way in the global operator approach to the quantization of two-dimensional conformal field theory. In addition, a proof of the infinitesimal and formal rigidity of the Witt algebra is presented.