bluuebunny/crossref_metadata_2025 huggingface dataset:
MULTIPROCESSOR RUNTIME SUPPORT FOR FINE-GRAINED, IRREGULAR DAGS
Authors: CHONG FREDERIC T. , SHARMA SHAMIK D. , BREWER ERIC A. , SALTZ JOEL
Published: November 2004

We examine multiprocessor runtime support for fine-grained, irregular directed acyclic graphs (DAGs) such as those that arise from sparse-matrix triangular solves. We conduct our experiments on the CM-5, whose lower latencies and active-message support allow us to achieve unprecedented speedups for a general multiprocessor. Where as previous implementations have maximum speedups of less than 4 on even simple banded matrices, we are able to obtain scalable performance on extremely small and irregular problems. On a matrix with only 5300 rows, we are able to achieve scalable performance with a speedup of 34 for 128 processors, resulting in an absolute performance of over 33 million double-precision floating point operations per second.

We achieve these speedups with non-matrix-specific methods which are applicable to any DAG. We compare a range of run-time preprocessed and dynamic approaches on matrices from the Harwell-Boeing benchmark set. Although precomputed data distributions and execution schedules produce the best performance, we find that it is challenging to keep their cost low enough to make them worthwhile on small, fine-grained problems.

Additionally, we find that a policy of frequent network polling can reduce communication overhead by a factor of three over the standard CM-5 policies. We present a detailed study of runtime overheads and demonstrate that send and receive processor overhead still dominate these applications on the CM-5. We conclude that these applications would highly benefit from architectural support for low-overhead communication.
STRUCTURE AND METASTABILITY OF THE EL2 DEFECT IN GaAs
Authors: TRAUTMAN P. , BARANOWSKI J.M.
Published: November 2004

EL2, the dominant native deep donor in GaAs , is one of few observed intrinsic defects in III-V semiconducting compounds. It is particularly interesting because it can be transformed to an excited metastable state through illumination of the crystal at low temperature. This article reviews experimental data on EL2 with emphasis on the reliable results that allowed the determination of the microscopic structure of this puzzling defect. Theoretical results, which help to understand and systematize the experimental data, are recalled. This article provides a survey of the present understanding of the microscopic structure and the mechanism of metastability of EL2. Particular attention is given to a recent experiment, performed by the present authors, that determined the spatial symmetry of EL2 in the metastable state. In our opinion, the properties of EL2 are best understood in the framework of the model identifying the normal (ground) state of the defect with the isolated arsenic-antisite As Ga and the metastable state with the tightly bound gallium-vacancy-arsenic-interstitial VGaAsi defect pair of trigonal symmetry.
FRIEDEL OSCILLATIONS ON A SQUARE LATTICE
Authors: MAHAN G.D.
Published: November 2004

An impurity in a conductor will cause oscillations in the charge density near the impurity. We calculate these Friedel Oscillations for impurities on a square lattice while using the tight-binding model. Far from the impurity the oscillations are described by a set of phase shifts. These are the same phase shifts which enter the Friedel Sum Rule.
INFLUENCE OF CHIRAL SYMMETRY ON THE CRITICAL BEHAVIOR OF STACKED TRIANGULAR ANTIFERROMAGNETS
Authors: WEBER H. , BECKMANN D. , WOSNITZA J. , LÖHNEYSEN H.v. , VISSER D.
Published: November 2004

We review and extend our recent specific-heat results of three antiferromagnetic quasi-onedimensional magnets, CsMnBr 3, CsNiCl 3, and CsMnI 3, with chiral symmetry. In zero field, CsMnBr 3 exhibits an unusually large critical specific-heat exponent α in good agreement with predictions for chiral XY symmetry. The anisotropy-crossover exponent ɸ has been determined in low fields applied perpendicular to the c axis. ɸ is clearly smaller than unity and differs from theoretical predictions. For CsNiCl 3 we find a crossover in fields B||c from conventional universality behavior for B=0 to chiral Heisenberg behavior at the multicritical point BM=2.3 T and further to chiral XY behavior at still higher fields. The critical exponents and also the amplitude ratios of the specific heat are in excellent agreement with theory. A magnetic field applied 13° off the c axis modifies the phase diagram, but the critical parameters remain essentially unchanged. Finally, specific-heat measurements of CsMnI 3 confirm the crossover for easy-axis antiferromagnets with chiral symmetry and yield an exponent α=0.28±0.06 at the multicritical point. At 7 T, we find α=0.33±0.06. These values are again in very good agreement with the predictions for the chiral Heisenberg and chiral XY universality classes.
LATTICE DYNAMICS OF THE BINARY APERIODIC CHAINS OF ATOMS I: FRACTAL DIMENSION OF PHONON SPECTRA
Authors: SALEJDA WŁODZIMIERZ
Published: November 2004

The microscopic harmonic model of lattice dynamics of the binary chains of atoms is formulated and studied numerically. The dependence of spring constants of the nearest-neighbor (NN) interactions on the average distance between atoms are taken into account. The covering fractal dimensions [Formula: see text] of the Cantor-set-like phonon spec-tra (PS) of generalized Fibonacci and non-Fibonaccian aperiodic chains containing of 16384≤N≤33461 atoms are determined numerically. The dependence of [Formula: see text] on the strength Q of NN interactions and on R=mH/mL, where mH and mL denotes the mass of heavy and light atoms, respectively, are calculated for a wide range of Q and R. In particular we found: (1) The fractal dimension [Formula: see text] of the PS for the so-called goldenmean, silver-mean, bronze-mean, dodecagonal and Severin chain shows a local maximum at increasing magnitude of Q and R>1; (2) At sufficiently large Q we observe power-like diminishing of [Formula: see text] i.e. [Formula: see text], where α=−0.14±0.02 and α=−0.10±0.02 for the above specified chains and so-called octagonal, copper-mean, nickel-mean, Thue-Morse, Rudin-Shapiro chain, respectively.
SOME NEW POSSIBILITIES OF SUPERHEATED SUPERCONDUCTING GRAIN (SSG) DETECTOR CHARACTERISTICS IMPROVEMENT
Authors: GEVORGYAN S.G.
Published: November 2004

This work is devoted to presentation the detail study results concerning the superconductivity destruction processes in solid colloids of superheated superconducting tin grains (SSG) under the influence of x rays of various energy and intensity, at different values of temperature and applied magnetic field. The research results have revealed the existence of a SSG detector optimal operating mode, permitting the formulation of some practical recipes for improvement of its characteristics. While solving the problem, our group came to the conclusion that more or less serious step forward in the creation of up-to-date and moreover future SSG detectors of ionizing radiation and exotic elementary particles could only be made by significantly improving the preparation technology of micron-size grains and colloids on their basis, and the detailed study of the physics of metastable superheated state of grained superconducting system, as well as by perfecting the old traditional and elaborating the new methods of researches of the above mentioned and analogous objects. This has required the preparation and investigation of a great number of solid colloids of tin spherical grains in paraffin matrix with different sizes of granules and with various average distances between the grains in suspension.
GUTZWILLER’S OCTAGON AND THE TRIANGULAR BILLIARD T*(2,3,8) AS MODELS FOR THE QUANTIZATION OF CHAOTIC SYSTEMS BY SELBERG’S TRACE FORMULA
Authors: NINNEMANN HOLGER
Published: November 2004

Two strongly chaotic systems are investigated with respect to quantization rules based on Selberg’s trace formula. One of them results from the action of a particular strictly hyperbolic Fuchsian group on the Poincaré disk, leading to a compact Riemann surface of genus g=2. This Fuchsian group is denoted as Gutzwiller’s group. The other one is a billiard inside a hyperbolic triangle, which is generated by the operation of a reflection group denoted as T*(2,3,8). Since both groups belong to the class of arithmetical groups, their elements can be characterized explicitly as 2×2 matrices containing entries, which are algebraic numbers subject to a particular set of restrictions. In the case of Gutzwiller’s group this property can be used to determine the geodesic length spectrum of the associated dynamical system completely up to some cutoff length. For the triangular billiard T*(2,3,8) the geodesic length spectrum is calculated by building group elements as products of a suitable set of generators and separating a unique representative for each conjugacy class.

The presence of reflections in T*(2,3,8) introduces additional classes of group elements besides the hyperbolic ones, which correspond to periodic orbits of the dynamical system. Due to different choices of boundary conditions along the edges of the fundamental domain of T*(2,3,8), several quantum mechanical systems are associated to one classical system. It has been observed, that these quantum mechanical systems can be divided into two classes according to the behavior of their spectral statistics. This peculiarity is examined from the point of view of classical quantities entering quantization rules. It can be traced back to a subtle influence of the boundary conditions, which introduces contributions from non-periodic orbits for one of the two classes.
HEAT LOCALIZATION EFFECTS IN PROBLEMS OF ICF (INERTIAL CONFINEMENT FUSION)
Authors: KURDYUMOV S.P. , SAMARSKII A.A. , ZMITRENKO N.V.
Published: November 2004

One of the most dangerous losses in ICF plasma is the loss due to an electron heat conductivity. It is shown that if the processes of a plasma heating develop under blowup regime then these losses can be eliminated due to an effect of heat localization.
EQUATIONS OF EVOLUTION NONLINEAR IN THE FLUXES IN INFORMATIONAL STATISTICAL THERMODYNAMICS
Authors: VASCONCELLOS ÁUREA ROSAS , LUZZI ROBERTO , GARCIA-COLIN LEOPOLDO S.
Published: November 2004

The Nonequilibrium Statistical Operator Method offers a quite appropriate mechano-statistical framework to irreversible thermodynamics, providing what may be termed as Informational Statistical Thermodynamics. Such scheme, which encompasses and enlarges Extended Irreversible Thermodynamics allows for the construction, at the microscopic (molecular) level, of equations of evolution for the fluxes that replace and correct the usual phenomenological constituve equations of Classical Irreversible Thermodynamics. In the present paper we show how IST allows the retrieval of the equations of evolution of EIT (the so called Maxwell-Cattaneo-Vernotte equations) including non-linearities in the fluxes. Besides evidencing such terms, the approach allows us to derive expressions for the kinetic coefficients on the basis of averages over the nonequilibrium informational statistical ensemble that describes the macroscopic state of the system.
UNITY RESONANCE AND UNDER-UNITY RESONANCE CONDITIONS IN ASYMMETRICAL DOUBLE-BARRIER STRUCTURES
Authors: ZHAO X.D. , YAMAMOTO H. , TANIGUCHI K.
Published: November 2004

Resonant tunneling is studied theoretically in asymmetrical double-barrier structures with arbitrary potential profile. Analytical expressions of the transmission coefficient and resonance condition are derived by taking into account the mass difference between the well and barrier layers. It is confirmed that resonant tunneling with unity resonant transmission or under-unity resonant transmission may occur in asymmetrical double-barrier structures. Two independent conditions are required for unity resonant transmission: one is the Phase Difference Condition for Resonance (PDCR) and the other is the Maximum Condition for the Peak Value (MCPV). The under-unity resonant transmission occurs when only PDCR holds. Furthermore, wave functions of an electron at resonance level are calculated and the confining phenomenon is studied.
HIGH RESOLUTION CALORIMETRIC STUDIES AT PHASE TRANSITIONS OF ALKYLCYANOBIPHENYL LIQUID CRYSTALS CONFINED TO SUBMICRON SIZE CYLINDRICAL CAVITIES
Authors: FINOTELLO DANIELE , IANNACCHIONE GERMANO S.
Published: November 2004

We review results of a high resolution systematic study of the specific heat for alkyl-cyanobiphenyl liquid crystals confined to the 0.2µm diameter cylindrical pores Anopore membranes. The nematic director alignment at the pore wall is varied from homeotropic to tangential by pore surface treatment. Several phenomena are uncovered by these studies which probed the weakly first order nematic to isotropic, the continuous smectic-A to nematic and the first order smectic-A to isotropic phase transitions. The specific heat is strongly dependent on the nematic director configuration, and confinement effects are remarkably distinct according to the order of the phase transition. The influence of elastic distortions and surface ordering and disordering effects are evident. Despite considerable departures from bulk behavior with regards to specific heat peaks size, rounding and width, and transition temperature shifts, a bulk-like critical behavior appears to be retained. The formation of smectic translational order within the pores is hindered for those liquid crystals that also possess a nematic phase. The average scalar order parameter temperature dependence is extracted from the specific heat results using a simplified Landau-de Gennes type of model, and is shown to be consistent with nuclear magnetic resonance results.
IMPROVEMENT OF THE VIEWING ANGLE FOR DISPLAY DEVICES WITH GRAY SCALE
Authors: BOS PHILIP J.
Published: November 2004

A liquid crystal electro-optical effect with an optically “self-compensating” director configuration is proposed to provide a device that has a wide angle of view at all gray levels. Calculations and data are presented to show the beneficial results of coupling a tunable birefringence L.C. device that has reverse pretilt alignment with a negative birefringence compensator plate.
MULTIPOLE MATRIX ELEMENTS FOR DH-SYSTEMS AND THEIR ASYMPTOTICS
Authors: TARASOV V.F.
Published: November 2004

A “DH-system” is defined as a multidimensional hydrogen atom (or its one-particle analogue), D≥1. Investigating many Coulomb problems in ℝD it is necessary to know exact analytical expressions of multipole matrix elements D for DH-systems, where q=(N, µ) is a set of parameters, N —"principal” and µ — "orbital” quantum numbers. The paper deals with the new method for the evaluation of similar matrix elements using new properties of Appell’s function F2(x, y) to the vicinity of the singular point (1, 1).

Such approach allows: 1) to get exact analytical expressions of these matrix elements (considering the selection rules) by means of Appell’s F2 (or Clausen’s 3F2) functions; 2) to reveal “latent” symmetry of diagonal matrix elements with respect to the point k0=−3/2, the above symmetry is connected with the property of Appell’s function F2 (1,1) mirror-like symmetry; 3) to find (exact) asymptotics of the off-diagonal matrix elements in terms of Horn’s function ψ1 (x, y); 4) to prove that the orthogonality of radial functions fNµ (D, r) over N and μ for DH-systems is connected with the properties of Appell’s F2 function to the vicinity of the singular point (1, 1), it generalizes the known result for 3H-atom by Pasternack and Sternheimer, J. Math. Phys.3, 1280 (1962).
INTEGRAL QUANTUM HALL EFFECT ON AN ANNULUS
Authors: AVISHAI Y. , KOHMOTO M.
Published: November 2004

Laughlin’s argument for the quantized Hall effect (for multiply connected geometries) in a form modified by Halperin is re-examined. In the present work we do not use the concept of an adiabatic change of the flux through the central hole. In these geometries, quantized plateaus exist even without disorder, thus the presence of localized states is not necessary. Rather, the existence of edge states plays an essential role. This property also persists in a strong electric field where linear response approximations fail. Numerical results are used to trace the disorder-induced breakdown of the Hall quantization in mesoscopic systems.
QUANTUM PERCOLATION
Authors: MOOKERJEE ABHIJIT , DASGUPTA INDRA , SAHA TANUSRI
Published: November 2004

In this review we describe and analyze various numerical attempts at understanding transport in the Quantum Percolation Model. We conclude that in two-dimensions all states are localized, though not necessarily exponentially localized, and that transport at low temperatures is dominated by probabilistically exceptional necklace-like resonant states.
GAUGE TRANSFORMATION AND VERTEX MODELS: A POLYNOMIAL FORMULATION
Authors: ROLLET G. , WU F. Y.
Published: November 2004

We consider vertex models on an arbitrary graph and propose a new polynomial formulation for its gauge transformation under which the partition function is invariant. Our formulation recovers in a simple way various, previously obtained results including the condition under which the vertex model is equivalent to an Ising model.
QUANTUM CORRECTIONS TO THE SEMICLASSICAL QUANTIZATION OF THE SU(3) SHELL MODEL
Authors: MANFREDI V. R. , SALASNICH L.
Published: November 2004

We apply the canonical perturbation theory to the semi-quantal Hamiltonian of the SU(3) shell model. Then, we use the Einstein–Brillowin–Keller quantization rule to obtain an analytical semi-quantal formula for the energy levels, which is the usual semiclassical one plus quantum corrections. Finally, a test on the numerical accuracy of the semiclassical approximation and of its quantum corrections is performed.
A GENERAL PROOF OF THE SAXON–HUTNER–LUTTINGER THEOREM IN DISORDERED DIATOMIC CHAINS
Authors: IGUCHI KAZUMOTO , YOSHIKAWA TOSHIO
Published: November 2004

The Saxon–Hutner–Luttinger theorem for the system of the one-dimensional disordered diatomic chains is reinvestigated and proved herein by using a very general mathematical scheme. This scheme does not depend upon the explicit forms of the transfer matrices in physical models. The method is applied to the continuous Schrödinger equation such as the delta-function Kronig–Penny model.
WANNIER FUNCTIONS AND FRACTIONAL QUANTUM HALL EFFECT
Authors: FERRARI R.
Published: November 2004

We introduce and study the Wannier functions for an electron moving in a plane under the influence of a perpendicular uniform and constant magnetic field. The relevance for the Fractional Quantum Hall Effect is discussed; in particular, it shown that an interesting Hartree–Fock state can be constructed in terms of Wannier functions.
THE MAGNETISM OF 3D IMPURITIES IN ALKALI METALS
Authors: ELZAIN M. E. , YOUSIF A. A.
Published: November 2004

Cluster calculation of the spin local magnetic moment of Fe in alkali metals is performed. A large Fe moment is retained, independent of the cluster size, even under relatively large compressions. The Fe 3d majority sub-band for both E g and T 2g symmetries are full, indicating a larger magnetic exchange splitting than the crystal field, as has been confirmed by direct computation. The 3d local density of states at the Fe site is found to consist of a single narrow, structureless peak independent of the alkali matrix; however, a small split appears in the minority sub-band in the case of Li and under compression in other metals. The bond order between the 3d atom and the neighboring alkali atoms is found to be vanishingly small for the majority electrons whereas the minority electrons retain a large value. The magnetic hyperfine field at the Fe site, due to the spin contact term, is found to be positive in spite of the large local moment. This is attributed to the cancellation resulting from the large positive valence contribution. The local magnetic moment and exchange splitting at 3d impurities in Na show a maximum at Cr and their ratio, which gives the exchange integral, increases from about 0.7 eV /µ B at Sc to about 0.9 eV /µ B at Ni. The Stoner type criterion is consistent with the retained local magnetic moment.
SELF-CONSISTENT PERTURBATION EXPANSIONS FOR SINGLE-IMPURITY-EXCHANGE-MODELS
Authors: GRUNEBERG J. , KEITER H.
Published: November 2004

Combining self-consistent perturbation theory with conventional renormalization group equations, a new systematic approach to Kondo-type models is developed, which yields analytical expressions for universal quantities like pseudofermion exponents and large effective couplings, usually out of reach from perturbative calculations. The new approach is related to the parquet-treatment of the x-ray-edge-singularity by Noziéres and coworkers in the late sixties and makes no use of a linearization of the band-electron-dispersion-relation, which is crucial for the Bethe Ansatz, conformal field theory, or numerical renormalization group treatment of the models. In addition it covers 1/N2-corrections to the well-known Non-Crossing-Approximation.
THERMODYNAMICS AND EXCITATIONS OF THE SUPERSYMMETRIC t-J MODEL
Authors: WILLIAMS ERIC D.
Published: November 2004

The free energy of the supersymmetric t-J model is expressed in terms of finite temperature excitations away from thermodynamic equilibrium. This reveals that the free energy has the form of noninteracting fermions with temperature dependent excitation spectra. We also discuss the ground state and zero temperature excitations.
MAGNETIZATION AND INTRAGRANULAR CRITICAL CURRENT DENSITY IN Yb1Ba2Cu3O7−x HIGH TEMPERATURE SUPERCONDUCTOR
Authors: MAHMOOD RAANA , KHAN M. NASIR , ZAFAR M. S. , KHWAJA FARID A. , WAHEED A.
Published: November 2004

The Yb 1 Ba 2 Cu 3 O 7−x samples have been prepared by the solid state reaction using the appropriate amount of Yb 2 O 3, BaCO 3, and CuO powders and characterized them using X-ray diffraction and electrical resistivity techniques. The X-ray diffraction pattern of the sample shows an orthorhombic structure refined in the space group Pmmm. The critical current densities are calculated from magnetization measurements over a temperature range 77 K to 86 K, and in magnetic fields up to 2 KOe. The intragrain critical current density is estimated to range from 5.24 × 106 ( A/cm 2) at an applied field of 0.2 KOe to 1.01 × 106 ( A/cm 2) at an applied field of 2 KOe at T = 77 K in this sample.
COMPUTING THE FRÉCHET DISTANCE BETWEEN TWO POLYGONAL CURVES
Authors: ALT HELMUT , GODAU MICHAEL
Published: November 2004

As a measure for the resemblance of curves in arbitrary dimensions we consider the so-called Fréchet-distance, which is compatible with parametrizations of the curves. For polygonal chains P and Q consisting of p and q edges an algorithm of runtime O(pq log(pq)) measuring the Fréchet-distance between P and Q is developed. Then some important variants are considered, namely the Fréchet-distance for closed curves, the nonmonotone Fréchet-distance and a distance function derived from the Fréchet-distance measuring whether P resembles some part of the curve Q.
AN OPTIMAL PARALLEL ALGORITHM FOR DETECTING WEAK VISIBILITY OF A SIMPLE POLYGON
Authors: CHEN DANNY Z.
Published: November 2004

The problem of detecting the weak visibility of an n-vertex simple polygon P is that of finding whether P is weakly visible from one of its edges and (if it is) identifying every edge from which P is weakly visible. In this paper, we present an optimal parallel algorithm for solving this problem. Our algorithm runs in O(log n) time using O(n/log n) processors in the CREW PRAM computational model, and is very different from the sequential algorithms for this problem. Based on this algorithm, several other problems related to weak visibility can be optimally solved in parallel.
NEW SPARSENESS RESULTS ON GRAPH SPANNERS
Authors: CHANDRA BARUN , DAS GAUTAM , NARASIMHAN GIRI , SOARES JOSE
Published: November 2004

Let G=(V, E) be an n-vertex connected graph with positive edge weights. A subgraph G′=(V, E′) is a t-spanner of G if for all u, v∈V, the weighted distance between u and v in G′ is at most t times the weighted distance between u and v in G. We consider the problem of constructing sparse spanners. Sparseness of spanners is measured by two criteria, the size, defined as the number of edges in the spanner, and the weight, defined as the sum of the edge weights in the spanner. In this paper, we concentrate on constructing spanners of small weight.

For an arbitrary positive edge-weighted graph G, for any t>1, and any ∈>0, we show that a t-spanner of G with weight [Formula: see text] can be constructed in polynomial time. We also show that (log2 n)-spanners of weight O(1) · wt(MST) can be constructed. We then consider spanners for complete graphs induced by a set of points in d-dimensional real normed space. The weight of an edge xy is the norm of the [Formula: see text] vector. We show that for these graphs, t-spanners with total weight O(log n) · wt(MST) can be constructed in polynomial time.
SEQUENTIAL AND PARALLEL ALGORITHMS FOR THE k CLOSEST PAIRS PROBLEM
Authors: LENHOF HANS-PETER , SMID MICHIEL
Published: November 2004

Let S be a set of n points in D-dimensional space, where D is a constant, and let k be an integer between 1 and [Formula: see text]. A new and simpler proof is given of Salowe’s theorem, i.e., a sequential algorithm is given that computes the k closest pairs in the set S in O(n log n+k) time, using O(n+k) space. The algorithm fits in the algebraic decision tree model and is, therefore, optimal. Salowe’s algorithm seems difficult to parallelize. A parallel version of our algorithm is given for the CRCW-PRAM model. This version runs in O((log n)2 log log n) expected parallel time and has an O(n log n log log n+k) time-processor product. Finally, actual running times are given of an implementation of our sequential algorithm.
CUTTINGS AND APPLICATIONS
Authors: BERG MARK DE , SCHWARZKOPF OTFRIED
Published: November 2004

We prove a general lemma on the existence of (1/r)-cuttings of geometric objects in Ed that satisfy certain properties. We use this lemma to construct (1/r)-cuttings of small size for arrangements of line segments in the plane and arrangements of triangles in 3-space; for line segments in the plane we obtain a cutting of size O(r+Ar2/n2), and for triangles in 3-space our cutting has size O(r2+c+Ar3/n3). Here A is the combinatorial complexity of the arrangement. Finally, we use these results to obtain new results for several problems concerning line segments in the plane and triangles in 3-space.
LOGARITHMIC-TIME LINK PATH QUERIES IN A SIMPLE POLYGON
Authors: ARKIN ESTHER M. , MITCHELL JOSEPH S.B. , SURI SUBHASH
Published: November 2004

We develop a data structure for answering link distance queries between two arbitrary points in a simple polygon. The data structure requires O(n3) time and space for its construction and answers link distance queries in O(log n) time, after which a minimum-link path can be reported in time proportional to the number of links. Here, n denotes the number of vertices of the polygon. Our result extends to link distance queries between pairs of segments or polygons. We also propose a simpler data structure for computing a link distance approximately, where the error is bounded by a small additive constant. Finally, we also present a scheme for approximating the link and the shortest path distance simultaneously.
EFFICIENT ALGORITHMS FOR SOLVING DIAGONAL VISIBILITY PROBLEMS IN A SIMPLE POLYGON
Authors: KIM SOO-HWAN , SHIN SUNG YONG , CHWA KYUNG-YONG
Published: November 2004

A diagonal guard is a guard capable of moving along an edge or an internal diagonal in a polygon. A polygon which can be guarded by a diagonal guard is called diagonal-visible. We consider the following three problems concerning the diagonal visibility in a polygon P. First, determine whether or not a guard diagonal exists in P, i.e., P is diagonal-visible. Second, compute all guard diagonals of P. Third, given a query diagonal, determine whether or not it is a guard diagonal. For these problems, we construct a data structure for keeping all guard diagonals in O(n log n) time and O(n) space. Using this data structure, we show that these problems can be solved in O(n log n), O(n log n+k), and O(1) time, respectively, where k is the number of guard diagonals.
IRREDUCIBLE COMPLEX CHARACTERS OF THE FULL AFFINE GROUP
Authors: DARAFSHEH M.R. , TARKHORANI M. RAJABI , DANESHKHAH A.
Published: November 2004

In this paper we describe how the entire complex character table of the affine subgroup of the general linear group Hn can be constructed inductively. In particular a number of certain irreducible characters of Hn which were studied by Gow [5] are obtained. We also describe some irreducible characters of the affine symplectic group. In all cases the powerful and interesting method of B. Fischer is employed.
SUM-TRANSLATION AND SYMMETRY OPERATORS AND INTEGRALITY OF HYPERGEOMETRIC LINEAR COEFFICIENTS
Authors: PICON P.A.
Published: November 2004

We define two operators acting on the product-quotients of factorials of linear forms: the sum-translation and the symmetry. New integral quotients can be obtained this way. We also exhibit several product-quotients which are integers among them a few with parameters. Finally, we point out the relation between these quotients and Chebychev’s approach to the prime-number theorem.
MULTILINEAR IDENTITIES OF THE ALGEBRAS OVER A FIELD OF CHARACTERISTIC P
Authors: KEMER ALEXANDER
Published: November 2004

We prove the theorem: Any associative PI-algebra over a field of characteristic p satisfies all the multilinear identities of the algebra of matrices of some finite order.
SYNCHRONIZATION OF TWO INTERACTING FINITE AUTOMATA
Authors: MAZOYER JACQUES
Published: November 2004

The Firing Squad Synchronization Problem with non uniform delays was recently solved by T. Jiang. In this paper, we study a very particular case: the synchronization of two finite automata. Two finite automata communicates, but the delay of communication is great in comparison with the duration of a state transition. We show that there exist solutions in time 2Δ(⌈ log m Δ⌉)+Δ (for any natural m). This implies that there does not exist an optimal solution (in the sense of K. Kobayashi) to the Firing Squad with non uniform delays. We show also that if the communication between the two automata are not symmetric the synchronization cannot be obtained.
A NEW KIND OF SINGULAR STIFF PROBLEMS AND APPLICATION TO THIN ELASTIC SHELLS
Authors: CAILLERIE D. , SANCHEZ-PALENCIA E.
Published: November 2004

We consider the asymptotic behavior of the solution of a class of problems involving a small parameter ε and ε2. This generalizes the “singular stiff” problems arising in classical thin shell theory. The new problems appear in theory of composite shells, when the local structure implies coupling between membrane stresses and flexions. According to specific hypotheses, this kind of problems contains singular perturbations and penalty problems where the limit solution belongs to a subspace G1 of the general configuration space V. In addition to the coercive problem, spectral properties are considered in the small and medium frequency ranges, including spectral families in the case without compactness.
POSTURE AND MOVEMENT IN PREGNANCY
Authors: DIVIETI L. , GALLI M. , SALVI R.
Published: November 2004

The aim of this study is to investigate the effects caused by increasing weight of maternal abdomen on the vertebral column.

We study this argument because women with typical pathologies of vertebral column as scoliosis present, after pregnancy, a worsening of pathology.

The progression of scoliosis in pregnant patients presents one of the most debatable and not yet clarified topic for the inherent hazard for mother and fetus in the traditional X-ray examination.

For this work, the posture and movement of six pregnant subjects, three females bearing an artificial abdomen and two men too, have been analyzed using a particular equipment (EL.I.TE) that is not dangerous for patients.

We analyze also the effects on the abdominal skin (ladders) due to the abdomen extension for fetus development studying a function which gives an approximation of abdominal profile, using a hydrodynamic model, to calculate the volume and the weight of the abdomen in the different pregnancy periods and also to analyze the causes of ladders.
EQUILIBRIUM VELOCITY DISTRIBUTION FUNCTIONS FOR A KINETIC MODEL OF TWO-PHASE FLOWS
Authors: SAINSAULIEU LIONEL
Published: November 2004

We consider a cloud of solid particles in a gas flow. The cloud is described by a probability density function which satisfies a kinetic equation. The gas flow is modeled by Navier-Stokes equations. The two phases exchange momentum and energy. We obtain the entropy balance of the gas flow and deduce some bounds for the volume fraction of the gas phase. Writing the entropy balance for the dispersed phase enables one to determine the particles equilibrium velocity distribution function when the gas flow is known.
GLOBAL EXISTENCE, ASYMPTOTICS AND UNIQUENESS FOR THE REFLECTION KERNEL OF THE ANGULARLY SHIFTED TRANSPORT EQUATION
Authors: JUANG JONQ , HSING CHIA LIN , NELSON PAUL
Published: November 2004

A nonlinear integrodifferential initial value problem, which is induced from a “simple transport model,” is investigated. The underlying equation contains two parameters c and α. Here c (c≥0) denotes the fraction of the scattering per collision and α (0≤α≤1) is an angular shift. In this paper, we exploit the relationship between the solution in the half space and that in slab geometry. We are thus able to show that the problem has a unique, positive, uniformly bounded and globally defined solution for 0≤c≤ 1 and 0≤α≤1. Moreover, it is shown that such global solution converges to the minimal positive solution of the half space problem as the spatial variable approaches ∞ (i.e. the slab becomes thicker).
ON A BOUNDARY VALUE PROBLEM FOR THE PLANE BROADWELL MODEL: EXACT SOLUTIONS AND NUMERICAL SIMULATION
Authors: BOBYLEV A.V. , GABETTA E. , PARESCHI L.
Published: November 2004

The initial boundary value problem for the Broadwell model equations in a half infinite channel with an infinitely small hole is considered. It is proved that this boundary value problem has no unique solution for sufficiently large concentration of the gas. There are at least two different solutions, we have constructed them in explicit form.

The existence of stationary solutions for the corresponding initial boundary value problem is then numerically investigated. The results indicate a unique asymptotic behavior of the model, very close to one of the two predicted stationary solutions.
CONVERGENCE OF THE DISCONTINUOUS GALERKIN FINITE ELEMENT METHOD FOR HYPERBOLIC CONSERVATION LAWS
Authors: JAFFRE J. , JOHNSON C. , SZEPESSY A.
Published: November 2004

We prove convergence of the discontinuous Galerkin finite element method with polynomials of arbitrary degree q≥0 on general unstructured meshes for scalar conservation laws in multidimensions. We also prove for systems of conservation laws that limits of discontinuous Galerkin finite element solutions satisfy the entropy inequalities of the system related to convex entropies.
STUDY OF THE MATHEMATICAL MODEL FOR A POLYMERIZATION PROBLEM
Authors: MANNUCCI PAOLA
Published: November 2004

We analyze a mathematical model for a problem concerning the cementation of an endomedullary infibulum. The cement used is a polymer that solidifies in situ generating heat.

We consider a problem in cylindrical symmetry in which the degree of polymerization and the temperature are the unknown functions. We prove the existence and uniqueness of a classical solution global in time.
A REACTION INFILTRATION PROBLEM: EXISTENCE, UNIQUENESS, AND REGULARITY OF SOLUTIONS IN TWO SPACE DIMENSIONS
Authors: CHADAM JOHN , CHEN XINFU , GIANNI ROBERTO , RICCI RICCARDO
Published: November 2004

In this paper, we consider a reaction infiltration problem consisting of a parabolic equation for the concentration, an elliptic equation for the pressure, and an ordinary differential equation for the porosity. We establish global existence, uniqueness and regularity of the solution in a two-dimensional finite strip (−M, M)×(0, 1) and the existence and partial regularity of solutions in an infinite strip (−∞, ∞)×(0, 1).
POINTWISE BOUNDS AND SPATIAL DECAY ESTIMATES IN HEAT CONDUCTION PROBLEMS
Authors: PAYNE L.E. , PHILIPPIN G.A.
Published: November 2004

In this paper we derive a new maximum principle for the absolute value of the gradient of a solution to the heat equation. We then apply this principle to obtain explicit bounds in the associated Dirichlet problem. Finally we derive explicit pointwise St-Venant type spatial decay estimates for solutions of certain initial-boundary value problems and their gradients in the case of unbounded domains.
TRAVELING WAVES FOR A SIMPLE DIFFUSIVE EPIDEMIC MODEL
Authors: HOSONO YUZO , ILYAS BILAL
Published: November 2004

We investigate the existence of traveling wave solutions for the infective-susceptible two-component epidemic model. The model system is described by reaction-diffusion equations with the nonlinear reaction term of the classical Kermack-McKendric type. The diffusion coefficients of infectives and susceptibles are assumed to be positive constants d1 and d2 respectively. By the shooting argument with the aid of the invariant manifold theory, we prove that there exists a positive constant c* such that the traveling wave solutions exist for any c≥c*. The minimal wave speed c* is shown to be independent of d2 and to have the same value as that for d2=0.
EXISTENCE, UNIQUENESS AND ASYMPTOTIC BEHAVIOUR FOR A MULTI-STAGE EVOLUTION PROBLEM OF AN AGE-STRUCTURED POPULATION
Authors: MATUCCI S.
Published: November 2004

The theory of semigroups of bounded linear operators in L1-like Banach spaces is employed to show the existence and uniqueness of a triple of non-negative functions representing the solution of a model of evolution of a population distributed in three stages of individuals, each of them being dependent on his own age and one stage also on mother age. The differential equations involved are linear and are coupled through linear boundary conditions. The detailed study of the spectrum of the linear, closed operator related to the system allows to obtain estimates for the asymptotic time behaviour of the solution; these results may be considered as a generalization of the Sharpe-Lotka theorem. Finally, the analytical structure of the solution is given.
A TOOLBOX FOR ANALYZING PROGRAMS
Authors: ANDERSON SCOTT D. , HART DAVID M. , WESTBROOK DAVID L. , COHEN PAUL R.
Published: November 2004

As program behavior becomes complex, it’s increasingly important to analyze their behavior statistically. The article describes two separate but synergistic tools for statistically analyzing large Lisp programs. The first tool, called CLIP (Common Lisp Instrumentation Package), allows the researcher to define and run experiments, including experimental conditions (parameter values of the planner or simulator) and data to be collected. The data are written out to data files that can be analyzed by statistics software. The second tool, called CLASP (Common Lisp Analytical Statistics Package), allows the researcher to analyze data from experiments by using graphics, statistical tests, and various kinds of data manipulation. CLASP has a graphical user interface (using CLIM, the Common Lisp Interface Manager) and also allows data to be directly processed by Lisp functions. Finally, the paper describes a number of other data-analysis modules that have been added to work with CLIP and CLASP.
AUTOMATED KNOWLEDGE ACQUISITION FROM ENCYCLOPEDIC TEXTS
Authors: GOMEZ FERNANDO , HULL RICHARD , SEGAMI CARLOS
Published: November 2004

A computational model for the acquisition of knowledge from encyclopedic texts is described. The model has been implemented in a program, called SNOWY, that reads unedited texts from The World Book Encyclopedia, and acquires new concepts and conceptual relations about topics dealing with the dietary habits of animals, their classifications and habitats. The program is also able to answer an ample set of questions about the knowledge that it has acquired. This paper describes the essential components of this model, namely semantic interpretation, inferences and representation, and ends with an evaluation of the performance of the program, a sample of the questions that it is able to answer, and its relation to other programs of similar nature.
TWO ALGORITHMS FOR INCREMENTAL CONSTRUCTION OF DIRECTED ACYCLIC WORD GRAPHS
Authors: SGARBAS KYRIAKOS N. , FAKOTAKIS NIKOS D. , KOKKINAKIS GEORGE K.
Published: November 2004

In this paper we present two algorithms for building lexicons in Directed Acyclic Word-Graphs (DAWGs). The two algorithms, one for deterministic and the other for non-deterministic DAWGs, can be used instead of the traditional subset construction method. Although the proposed algorithms do not produce the optimal DAWG (i.e., the one with the minimum number of states), they are simple, fast and able to build the DAWG incrementally, as new words are added to the lexicon. Thus, building large lexicons in a DAWG structure becomes an easy task, even for a modest computer.
MULTIPARAMETER QUANTUM FORMS OF THE ENVELOPING ALGEBRA $U_{{\mathfrak g}{\mathfrak l}_N}$ RELATED TO THE FADDEEV-RESHETIKHIN-TAKHTAJAN U(R) CONSTRUCTIONS
Authors: TOWBER JACOB
Published: November 2004

Two quantum enveloping algebras UR and ÛR are associated in [RTF] to any Yang-Baxter operator R. These are constructed as subalgebras of A(R)* with specific generating sets. Also, [RTF] construct specific relations on the generators for UR, leaving open the question whether these generate all relations on these generators—let us say R is “perfect” when this is the case.

Given an [Formula: see text] -tuple [Formula: see text] of nonzero elements qij,r in the groundfield, ([AST], [R], [S]) construct a multiparameter deformation [Formula: see text] of GLN associated with a Yang-Baxter operator [Formula: see text].

The method of ‘braiding maps’, introduced in [LT], is applied, in order to derive a PBW basis and a generators-and-relations presentation for a suitable generalization of [Formula: see text]. These results imply that [Formula: see text] is perfect, for generic [Formula: see text].

The construction [Formula: see text] is in some ways unsatisfactory if r is a root of 1. A construction [Formula: see text] is proposed, which is in some ways better behaved, coincides with [Formula: see text] if r is not a root of 1, and also makes sense over arbitrary commutative rings.
RIGIDITY OF GRAPH SYMMETRIES IN THE 3-SPHERE
Authors: FLAPAN ERICA
Published: November 2004

In this paper we show that, for any 3-connected graph G, if an automorphism of G is realizable by a homeomorphism of (S3, G) then there is an embedding of G such that that automorphism is induced by a finite order homeomorphism of (S3, G). We then use this result to characterize which automorphisms of an arbitrary complete graph can be induced by a homeomorphism of S3 for some embedding of the graph.
THE (2, ∞)-SKEIN MODULE OF WHITEHEAD MANIFOLDS
Authors: HOSTE JIM , PRZYTYCKI JÓZEF H.
Published: November 2004

To any orientable 3-manifold one can associate a module, called the (2, ∞)-skein module, which is essentially a generalization of the Jones polynomial of links in S3. For an uncountable collection of open contractible 3-manifolds, each constructed in a fashion similar to the classic Whitehead manifold, we prove that their (2, ∞)-skein modules are infinitely generated, torsion free, but not free. These examples stand in stark contrast to [Formula: see text], whose (2, ∞)-skein module is free on one generator. To each of these manifolds we associate a subgroup G of the rationals which may be interpreted via wrapping numbers. We show that the skein module of M has a natural filtration by modules indexed by G. For the specific case of the Whitehead manifold, we describe its (2, ∞)-skein module and associated filtration in greater detail.
PERTURBATIVE CHERN-SIMONS THEORY
Authors: BAR-NATAN DROR
Published: November 2004

We present the perturbation theory of the Chern-Simons gauge field theory and prove that to second order it indeed gives knot invariants. We identify these invariants and show that in fact we get a previously unknown integral formula for the Arf invariant of a knot, in complete agreement with earlier non-perturbative results of Witten. We outline our expectations for the behavior of the theory beyond two loops.
SOLUTIONS OF THE YANG-BAXTER EQUATIONS FROM BRAIDED-LIE ALGEBRAS AND BRAIDED GROUPS
Authors: MAJID SHAHN
Published: November 2004

We obtain an R-matrix or matrix representation of the Artin braid group acting in a canonical way on the vector space of every (super)-Lie algebra or braided-Lie algebra. The same result applies for every (super)-Hopf algebra or braided-Hopf algebra. We recover some known representations such as those associated to racks. We also obtain new representations such as a non-trivial one on the ring k[x] of polynomials in one variable, regarded as a braided-line. Representations of the extended Artin braid group for braids in the complement of S1 are also obtained by the same method.
AGGREGATING TRANSITIVE FUZZY BINARY RELATIONS
Authors: OVCHINNIKOV SERGEI
Published: November 2004

We discuss the aggregation problem for transitive fuzzy binary relations. An aggregation procedure assigns a group fuzzy binary relation to each finite set of individual binary relations. Individual and group binary relations are assumed to be transitive fuzzy binary relation with respect to a given continuous t-norm. We study a particular class of aggregation procedures given by quasi-arithmetic (Kolmogorov) means and show that these procedures are well defined if and only if the t-norm is Archimedean. We also give a geometric characterization of t-norms for which the arithmetic mean is a well-defined aggregation procedure.
FUZZY INFORMATION PROCESSING FOR EXPERT SYSTEMS
Authors: LEE KEON-MYUNG , LEE-KWANG HYUNG
Published: November 2004

This paper investigates the problems incurred when fuzzy values and certainty factors are used in rule-based knowledge representation. It proposes several measures for evaluating the satisfaction degree of fuzzy matching, fuzzy comparison and interval inclusion occurring in the course of inference for such knowledge representation. It introduces an inference method for such knowledge representation. In addition, it suggests a strategy for flexibly using and managing both conventional rules and fuzzy production rules in rule-based systems. Finally a fuzzy expert system shell, called FOPS5, designed to accommodate fuzzy information processing, is presented in consideration of the proposed methods.
ON THE APPLICATION OF A CLASS OF MICA OPERATORS
Authors: KELMAN ANTOINE , YAGER RONALD R.
Published: November 2004

Abstract: We discuss the MICA operators and show they provide a very general framework for modeling aggregation operators. We present a generic class of MICA operators that can be adapted to various type of situations through the tuning of parameters. These parameters can be set by a human expert or automatically learned from data through a genetic algorithm.
SELECTION OF α FOR α-HULL AND FORMULATION OF FUZZY α-HULL IN IR2
Authors: MANDAL DEBA PRASAD , MURTHY C.A.
Published: November 2004

A decade ago, Edelsbrunner et. al. introduced the concept of α-hulls for finding the shape of a planar set. But it still suffers from a major deficiency i.e., the single parameter α must be fine-tuned. The present article initially proposes a selection criterion of α for α-hulls in R2. Then the concept of α-hulls is extended to define the fuzzy α-hulls. The effectiveness of the fuzzy α-hulls and the proposed selection criterion of α is demonstrated on some artificially generated data sets. The convergence (with sample size) of both the crisp and fuzzy α-hulls, based on the proposed selection criterion of α, to the original pattern class has also been verified.