bluuebunny/crossref_metadata_2025 huggingface dataset:
HYPERON SUPERFLUIDITY IN NEUTRON STAR CORES
Authors: TAKATSUKA T. , NISHIZAKI S. , YAMAMOTO Y. , TAMAGAKI R.
Published: July 2002

Superfluidity of Λ-hyperons admixed in neutron star cores is investigated by a realistic approach and found to be realizable with the critical temperature of 108-9 K though in a restricted density region. In reference to the results of Λ, the possible occurence of the Σ-- and Ξ-- superfluidities is pointed out. The pairing effects of hyperons is also shown to be important in hypernuclear matter relevant to hypernuclei. In a treatment of a gap equation, the necessity to use a "bare" hyperon-hyperon interaction, instead of an "effective" one, is stressed.
INCOMMENSURATE STRUCTURE FACTOR IN A HOLE-DOPED SPIN-1 SYSTEM
Authors: BOSE INDRANI , CHATTOPADHYAY EMILY
Published: July 2002

The nickelate compound Y 2 BaNiO 5 is a spin-1 Haldane-gap antiferromagnet. The compound is doped with holes on replacing the off-chain Y 3+ ions by Ca 2+ ions. Inelastic neutron scattering (INS) experiments reveal the existence of sub-gap states on doping. A recent INS experiment provides evidence for an incommensurate double-peaked structure factor S(q) corresponding to the sub-gap states. In this paper, we formulate a microscopic theory for the origin of the incommensurate peaks.
UlTRAFAST LATTICE RELAXATION DYNAMICS OF EXCITON IN A QUAISI-1-D METAL-HALOGEN COMPLEX
Authors: SUGITA ATSUSHI , SAITO TAKASHI , KOBAYASHI TAKAYOSHI , YAMASHITA MASAHIRO
Published: July 2002

A quasi-one-dimensional halogen-bridged mixed-valence metal complex is studied by time-resolved pump and probe spectroscopy with sub-5 fs time resolution. Two kinds of oscillatory signals are observed, which are attributed to the wave packet motions both in an electronic ground state and in a self-trapped exciton (STE) state. The onset of the wave packet motion is found to be delayed by about 50 fs, comparing with the ideal wave packet in the electronic excited state. The delay reflects the thermalization process in a free exciton (FE) state and a lattice relaxation process from FE to STE states.
GEOMETRICALLY FRUSTRATED QUANTUM ANTIFERROMAGNETS AND SPIN-LIQUIDS
Authors: LHUILLIER C. , BERNU B. , MISGUICH G.
Published: July 2002

We briefly review experimental and theoretical results related to the problem of long range magnetic order in geometrically frustrated 2-dimensional quantum antiferromagnets. We show that 2-dimensional He3 at low coverage is a good candidate as a Spin-Liquid. We underline that sophisticated numerical studies of the spectra of such systems point at least to two different kinds of Spin-Liquids.
Structural Properties and Chemical Homogeneity of Underdoped La2-xMxCuO4 Cuprates (M = Sr, Ba)
Authors: Ferretti Maurizio , Magnone Edoardo , Napoletano Myrta
Published: July 2002

The present work reports a systematic and accurate study on crystal structure and chemical homogeneity of underdoped La 2-x M x CuO 4( M = Sr , Ba ). Samples' structural characterization performed by Rietveld refinement of XRD powder diffraction profiles provided an accurate working trendline for the dopant concentration determination. Furthermore FT-IR skeletal analysis and SIMS investigations ensured chemical homogeneity even for samples with very low dopant contents.
Influence of Polarization Rate and Dielectric Loss on ER Effects
Authors: Qiu Z. Y. , Zhang H. , Tang Y. , Zhou L. W. , Wei C. G. , Zhang S. H. , Korobko E. V.
Published: July 2002

A simplified model is considered to describe the resistive transport and diffusion of charge carriers within or around an ER active particle under influence of AC electric field and temperature. The effective polarization strength, dielectric constant and dielectric loss of the particle are derived from this model. Considered the effects of shear field, the criteria for ER activity are presented as ωτ >10-4, 1<d/λ<102 and ωτ d/λ<1 for ω<103s-1. The criteria determine the lower and upper limits of the polarization rate and dielectric loss of ER particles. The criteria are testified by the following experimental results. First, the measured lower limit of diatomite particle conductivity is 7.3×10-8S/m. Second, the shear stresses at the shear rates from 9.9 to 100 s -1 at 1kV/mm field start to rise with temperature from 25°C. Third, with decreasing shear rate or/and increasing electric field strength, the peaks of shear stress shift down the lower temperatures.
UPPER CRITICAL FIELD OF UNCONVENTIONAL SUPERCONDUCTORS FROM CHEMICAL EQUILIBRIUM
Authors: KALLIO A. , HISSA J. , HÄYRYNEN T. , BRÄYSY V.
Published: July 2002

We have shown previously that many normal state properties of high Tc superconductors in zero magnetic field can be understood in terms of a single universal function f(t) in the scaled variable t=T/T*, where T* is connected with temperature independent gap 2Δ=2kBT*, which gives the binding energy of a pair in analogy with dissociation of molecules. The function f(t) determines the fraction of bosons (B++) and fermions (h+) at temperature T and it is obtained from the mathematical treatment of chemical equilibrium with respect to the reaction B++⇌ 2h+. Since for magnetic fields of reasonable strength the Zeeman energy is much smaller than the pseudo gap Δ~100K-800K, the function f(t) in the normal state is largely independent of magnetic field. The main effect of the magnetic field is to increase the tendency for bosons to localize. This means that the critical density nL for delocalization in the ab-plane direction and the critical density for superfluidity nc (≳ nL) both increase with magnetic field. This causes the corresponding temperatures TBL(H) and Tc(H) to go down with the field. Assuming a power law dependence nc(H)/nc(0)=1+AHμ, the upper critical fields for several heavy fermion compounds are shown to fall into a single curve. The purpose here is to show that the upper critical field Hc2(y) (y=Tc(H)/Tc(0)) can be expressed in a simple way in terms of f(t). We show that this theory predicts all the shapes of Hc2(y) observed in several unconventinal superconductors such as Tl 2 Ba 2 CuO 6+δ, with Tc=15 K.
NONLINEAR ANALYSIS OF DISPERSION FROM DOUBLE PERIODIC SEMICONDUCTOR GRATING
Authors: TIWARI D. C. , CHATURVEDI VANDANA
Published: July 2002

We have derived the dispersion relation for double GaAs semiconductor grating, using nonlinear boundary condition approach. The grating medium is assumed to non-magnetic and it has sinusoidal undulation of angular frequency ω on both side of the film. In the limit when plasma wavevector k p is greater than k‖ wavevector of the wave, we obtained two branches in the dispersion curve which corresponds to electrostatic charge disposition on the two sides of grating. In the limiting case k p < k‖, the grating radiate the electromagnetic field in the vicinity area.
A NEW APPROACH TO IDEAL AlGaAs MQW SOLAR CELLS
Authors: RIMADA J. C. , HERNÁNDEZ L.
Published: July 2002

A theoretical model has been developed which shows that the insertion of multi-quantum wells into the depletion region of a p-i(MQW)-n Al x Ga 1-x As solar cell can significantly enhance the conversion efficiencies. Open-circuit voltages, short-circuit current densities, I-V curves and conversion efficiencies have been calculated as functions of the well and barrier band gaps, width and depth of the wells, number of wells in the intrinsic region and the recombination rate in the interfaces. Particular emphasis is placed on calculation of absorption of the Al x Ga 1-x As quantum wells. These results are matched with p-i-n solar cells which are identical in all respects except that they do not have quantum wells. We demonstrated that for determined values of the studied parameters the conversion efficiencies of the quantum well solar cell is higher to corresponding cell without quantum wells.
Influence of Impurity Charge-State on the Temperature Dependence of the Electric-Field Gradient
Authors: Shitu Jorge , Pasquevich Alberto F. , Bibiloni Anibal G. , Rentería Mario , Requejo Felix G.
Published: July 2002

We present, for the first time, clear experimental evidence of the influence of the electronic configuration of probe-atoms on the temperature dependence of the electric-field gradient (EFG) tensor at impurity sites. We measured the EFG at 111 In →111 Cd and 181 Hf → 181 Ta impurity sites in a complete series of semiconducting and insulating compounds with the same crystalline structure, using the Perturbed-Angular-Correlation technique. The results of this systematic study show that while the principal component VZZ of the EFG increases with temperature at Cd-impurity sites, it decreases at Ta-impurity sites. This temperature dependence is associated with the redistribution of the electronic charge lack or excess located at the impurity center. A simple model is presented based on charge transfer from the probe to its neighbors, in terms of the acceptor and donor nature of the mentioned impurities.
A SURVEY OF COMPUTER VISION EDUCATION AND TEXT RESOURCES
Authors: MAXWELL BRUCE A.
Published: July 2002

This paper provides a survey of the variety of computer vision [CV] and image processing [IP] courses being taught at institutions around the world. The survey shows that, in addition to classic survey courses in CV/IP, there are many focused and multidisciplinary courses being taught that reportedly improve both student and faculty interest in the topic. It also demonstrates that students can successfully undertake a variety of complex lab assignments. In addition, this paper includes a comparative review of current textbooks and supplemental texts appropriate for CV/IP courses.
ELASTIC FACE RECOGNIZER: INVARIANT FACE RECOGNITION BASED ON ELASTIC GRAPH MATCHING MODEL
Authors: LEE RAYMOND S. T.
Published: July 2002

Human faces are difficult to interpret because they are highly variable. Over the last few decades, various techniques have been proposed for computer recognition of human faces. In this paper, we introduce an Elastic Graph Dynamic Link Model to automate the process of facial recognition. It is integrated with the Active Contour Model to provide an effective and efficient means of facial contour extraction and recognition. A portrait gallery of 100 distinct facial images is used for network training. Experimental results are presented for a database of 1,020 tested face images, which were obtained under conditions of widely varying facial expressions, viewing perspectives and image sizes. An overall average correct recognition rate of over 86% is attained.
AN UNUSUAL HOPF BIFURCATION: THE RAILWAY BOGIE
Authors: HASSARD BRIAN
Published: July 2002

The railway bogie model introduced by Cooperrider [1972] exhibits a Hopf bifurcation as the speed of the train v tr is increased. This Hopf bifurcation is unusual because the amplitude of the family of periodic solutions that arises, behaves locally like [Formula: see text] rather than like [Formula: see text]. The explanation seems to lie with the form of the creep forces. Because of these forces, the model is of class C1 but not C2 at the origin.
SYNCHRONIZATION AND CONTROL OF SPATIALLY EXTENDED SYSTEMS USING SENSOR COUPLING
Authors: JUNGE LUTZ , PARLITZ ULRICH , TASEV ZARKO , KOCAREV LJUPCO
Published: July 2002

We investigate the problem of synchronizing and controlling spatially extended systems. For this purpose a coupling scheme is introduced, that allows to synchronize and control the dynamics with only a few driving signals which are spatial averages of local regions. We estimate the optimal arrangement of the coupling signals and compare them with their usual periodic arrangement. The application in controlling, e.g. suppression of chaos, is demonstrated.
ON A TORSION-FREE WEAKLY BRANCH GROUP DEFINED BY A THREE STATE AUTOMATON
Authors: GRIGORCHUK ROSTISLAV I. , ŻUK ANDRZEJ
Published: July 2002

We study a torsion free weakly branch group G without free subgroups defined by a three state automaton which appears in different problems related to amenability, Galois groups and monodromy. Here and in the forthcoming paper [20] we establish several important properties of G related to fractalness, branchness, just infinitness, growth, amenability and presentations.
HNN EXTENSIONS OF SEMILATTICES
Authors: YAMAMURA AKIHIRO
Published: July 2002

The main purpose of this paper is to investigate properties of an HNN extension of a semilattice, to give its equivalent characterizations and to discuss similarities with free groups. An HNN extension of a semilattice is shown to be a universal object in a certain category and an F-inverse cover over a free group for every inverse semigroup in the category. We also show that a graph with respect to a certain subset of an HNN extension of a semilattice is a tree and that this property characterizes an HNN extension of a semilattice. Moreover, we look into three subclasses: the class of full HNN extensions of semilattices with an identity, the class of universally E-unitary inverse semigroups and the class of HNN extensions of finite semilattices. The first class consists of factorizable E-unitary inverse semigroups whose maximal group homomorphic images are free. We obtain a generalization of the Nielsen–Schreier subgroup theorem to this class. The second consists of inverse semigroups presented by relations on Dyck words. An inverse semigroup in the third class has a relatively easy finite presentation using a Dyck language and has solvable word problem.
COMBINING HIERARCHICAL FILTERING, FUZZY LOGIC, AND SIMULATION WITH SOFTWARE AGENTS FOR IP (INTELLECTUAL PROPERTY) SELECTION IN ELECTRONIC DESIGN
Authors: LIU JIAN , SHRAGOWITZ EUGENE , TSAI WEI-TEK
Published: July 2002

SAFIPS (Software Agents for IP Selection) environment is designed to improve quality and speed of finding IPs on Internet for SoC (System-on-Chip) projects. The software agents take responsibility for establishing communication with multiple suppliers of IPs and automatically retrieve information from their databases using metalanguage (XML), and data specifications compliant with ECIX (Electronic Component Information eXchange) specifications. The communication environment is based on Dictionaries for terminology and list of parameters, and on Registry for the list and web addresses of suppliers. The information obtained by software agents is analyzed by a system of fuzzy logic rules compiled in the process of a dialog between the customer and SA. The software agent asks the customer questions and provides templates for answers. The answers are automatically converted into the membership functions and fuzzy logic rules that are applied to evaluation of potential candidate IPs. As soon as replies to the query by SA start to come, data are analyzed by software agents and IPs can be excluded from further consideration if there is drastic mismatch between expected values and IP parameters and constraints. The remaining IPs are evaluated by the hierarchical system of rules and ranks are assigned to those which passed the preliminary tests. The top candidates are subjected to simulation together with the behavioral models provided by customers under supervision of software agent. The timing diagrams obtained from simulation are going to be analyzed to evaluate their equivalence. Only after that the system presents the candidate IPs for the final selection. The main goal to save valuable design time can be achieved by such system. The text is accompanied by an example.
CONCURRENT ABDUCTIVE LOGIC PROGRAMMING IN PANDORA
Authors: BAHGAT REEM , MOSTAFA OSAMA , PAPADOPOULOS GEORGE A.
Published: July 2002

The extension of logic programming with abduction (ALP) allows a form of hypothetical reasoning. The advantages of abduction lie in the ability to reason with incomplete information and the enhancement of the declarative representation of problems. On the other hand, concurrent logic programming is a framework which explores AND-parallelism and/or OR-parallelism in logic programs in order to efficiently execute them on multi-processor / distributed machines.

The aim of our work is to study a way to model abduction within the framework of concurrent logic programming, thus taking advantage of the latter's potential for parallel and/or distributed execution. In particular, we describe Abductive Pandora, a syntactic sugar on top of the concurrent logic programming language Pandora, which provides the user with an abductive behavior for a concurrent logic program. Abductive Pandora programs are then transformed into Pandora programs which support the concurrent abductive behavior through a simple programming technique while at the same time taking advantage of the underlying Pandora machine infrastructure.
MULTIRESOLUTION FOR SAT CHECKING
Authors: CHATALIC PHILIPPE , SIMON LAURENT
Published: July 2002

This paper presents a system based on new operators for handling sets of propositional clauses compactly represented by means of ZBDDs. The high compression power of such data structures allows efficient encodings of structured instances. A specialized operator for the distribution of sets of clauses is introduced and used for performing multiresolution on clause sets. Cut eliminations between sets of clauses of exponential size may then be performed using polynomial size data structures. The ZRES system, a new implementation of the Davis-Putnam procedure of 1960, solves two hard problems for resolution, that are currently out of the scope of the best SAT provers.
An Infinite Suite of Links–Gould Invariants
Authors: De Wit David
Published: July 2002

This paper describes a method to obtain state model parameters for an infinite series of Links–Gould link invariants LGm,n, based on quantum R matrices associated with the [Formula: see text] representations of the quantum superalgebras Uq[gl(m|n)]. Explicit details of the state models for the cases n=1 and m=1, 2, 3, 4 are supplied. Some gross properties of the link invariants are provided, as well as some explicit evaluations.
BRAID MONODROMY OF SPECIAL CURVES
Authors: Amram Meirav , Teicher Mina
Published: July 2002

In this article, we compute the braid monodromy of two algebraic curves defined over ℝ. These two curves are of complex level not bigger than 6, and they are unions of lines and conics. We use two different techniques for computing their braid monodromies. These results will be applied to computations of fundamental groups of their complements in [Formula: see text] and [Formula: see text].
THE COMBINATORIAL GAUSS DIAGRAM FORMULA FOR KONTSEVICH INTEGRAL
Authors: OCHIAI TOMOSHIRO
Published: July 2002

In this paper, we shall give an explicit Gauss diagram formula for the Kontsevich integral of links up to degree four. This practical formula enables us to actually compute the Kontsevich integral in a combinatorial way.
EXTREMAL BLACK HOLES AND THE LIMITS OF THE THIRD LAW
Authors: LIBERATI STEFANO , ROTHMAN TONY , SONEGO SEBASTIANO
Published: July 2002

Recent results of quantum field theory on a curved spacetime suggest that extremal black holes are not thermal objects and that the notion of zero temperature is ill-defined for them. If this is correct, one may have to go to a full semiclassical theory of gravity, including backreaction, in order to make sense of the third law of black hole thermodynamics. Alternatively it is possible that we shall have to drastically revise the status of extremality in black hole thermodynamics.
THERMAL QUASI-EQUILIBRIUM STATES ACROSS LANDAU HORIZONS IN THE EFFECTIVE GRAVITY OF SUPERFLUIDS
Authors: FISCHER UWE R. , VOLOVIK GRIGORI E.
Published: July 2002

We give an account of the physical behaviour of a quasiparticle horizon due to non-Lorentz invariant modifications of the effective spacetime experienced by the quasiparticles ("matter") for high momenta. By introducing a "relativistic" conserved energy–momentum tensor, we derive quasi-equilibrium states of the fluid across the "Landau" quasiparticle horizon at temperatures well above the quantum Hawking temperature. Nonlinear dispersion of the quasiparticle energy spectrum is instrumental for quasiparticle communication and exchange across the horizon. It is responsible for the establishment of the local thermal equilibrium across the horizon with the Tolman temperature being inhomogeneous behind the horizon. The inhomogeneity causes relaxation of the quasi-equilibrium states due to scattering of thermal quasiparticles, which finally leads to a shrinking black hole horizon. This process serves as the classical thermal counterpart of the quantum effect of Hawking radiation and will allow for an observation of the properties of the horizon at temperatures well above the Hawking temperature. We discuss the thermal entropy related to the horizon. We find that only the first nonlinear correction to the energy spectrum is important for the thermal properties of the horizon. They are fully determined by an energy of order E Planck (T/E Planck )1/3, which is well below the Planck energy scale E Planck , so that Planck scale physics is not involved in determining thermal quantities related to the horizon.
ON THE QUANTIZATION OF CHARGED BLACK HOLES
Authors: POLLOCK M. D.
Published: July 2002

The Wheeler–DeWitt equation for the wave function Ψ of the Schwarzschild black hole has been derived by Tomimatsu in the form of a Schrödinger equation, valid on the apparent horizon, using the two-dimensional Hamiltonian formalism of Hajicek and the radiating Vaidya metric. Here, the analysis is generalized to the Reissner–Nordström black hole. At constant charge Q, the evaporation rate is calculated from the solution for Ψ to be [Formula: see text], where k is a constant and [Formula: see text] are the radii of the outer event horizon and inner Cauchy horizon. In the extremal limit M → Q, however, the Hawking temperature [Formula: see text] tends to zero, suggesting, when the back reaction is taken into account, that the evaporation cannot occur this way and in agreement with the known discharging process of the hole via the Schwinger electron–positron pair-production mechanism. The more general charged dilaton black holes obtained from the theory L4 = [R4 - 2 (∇ Φ)2 - e-2aΦF2 ]/16π are also discussed, and it is explained why this quantization procedure cannot be applied when a is non-zero.
ANTI-DE SITTER WORMHOLE KINK
Authors: GONZÁLEZ-DÍAZ PEDRO F.
Published: July 2002

The metric describing a given finite sector of a four-dimensional asymptotically anti-de Sitter wormhole can be transformed into the metric of the time constant sections of a Tangherlini black hole in a five-dimensional anti-de Sitter spacetime when one allows light cones to tip over on the hypersurfaces according to the conservation laws of an one-kink. The resulting kinked metric can be maximally extended, then giving rise to an instantonic structure on the Euclidean continuation of both the Tangherlini time and the radial coordinate. In the semiclassical regime, this kink is related to the existence of closed timelike curves.
QUANTUM COSMOLOGY WITH A NONLINEAR BORN–INFELD TYPE SCALAR FIELD
Authors: LU H. Q. , HARKO T. , CHENG K. S.
Published: July 2002

A quantum model of gravitation interacting with a Born–Infeld type nonlinear scalar field φ is considered. The corresponding Wheeler–DeWitt equation can be solved analytically for both large and small [Formula: see text]. In the extreme limits of small and large cosmological scale factors the wave function of the Universe can also be obtained by applying the methods developed by Vilenkin and Hartle and Hawking. An inflationary Universe is predicted with the largest possible vacuum energy and the largest interaction between the particles of the nonlinear scalar field.
SELF-ENERGY EFFECTS IN THE OPTICAL ANISOTROPY OF GaP(001)
Authors: SCHMIDT W. G. , FATTEBERT J. L. , BERNHOLC J. , BECHSTEDT F.
Published: July 2002

We calculate the reflectance anisotropy for GaP(001)(2×4) surfaces using a real-space multigrid method and ab initio pseudopotentials. Our results obtained within DFT-LDA show good qualitative agreement with recent experiments. This holds in particular for the stoichiometric trends. A strong negative anisotropy at low photon energies is linked to the formation of Ga–Ga bonds along the [110] direction. There are discrepancies, however, with respect to the line shape and the energetic positions of characteristic peaks. Substantial improvement is achieved by using a numerically efficient GW approach with approximations for local-field effects and dynamical screening. We find that the spectral features related to transitions between surface perturbed bulk wave functions are more strongly affected by self-energy corrections than anisotropies directly linked to surface electronic states.
SIMULTANEOUS DORSAL DISLOCATION OF DOUBLE JOINTS IN A FINGER: A REPORT OF TWO CASES
Authors: Ishizuki Masafumi , Saito Norio , Gen Taishin
Published: July 2002

The authors have experience of a case of simultaneous dorsal dislocation of the interphalangeal joints of the PIP joint and CM joint of the little finger. The latter case of finger dislocation was combined with a wound at the volar aspect of the PIP joint. Results of both cases were acceptable.
PRONATOR TERES SYNDROME ASSOCIATED WITH MONONEURITIS MULTIPLEX IN POLYARTERITIS NODOSA
Authors: Asami Akihiko , Takayama Go , Hotokebuchi Takao
Published: July 2002

A case of pronator teres syndrome associated with mononeuritis multiplex in polyarteritis nodosa is reported. External neurolysis of the median nerve at the proximal forearm and prednisolone were effective for treatment of the disease.
REFINING THE QUADRATIC APPROXIMATION FORMULA FOR AN AMERICAN OPTION
Authors: WONG WOON KWONG , XU KAI
Published: July 2002

The aim of this paper is to provide a more refined approximation for the valuation of an American option, based on the quadratic approximation method. We not only show that the result using the old method is the special case of our method, but also investigate the qualitative behavior of American options with respect to a certain new parameter.
TAYLOR MAP ON GROUPS ASSOCIATED WITH A II1-FACTOR
Authors: GORDINA MARIA
Published: July 2002

A notion of the heat kernel measure is introduced for the L2 completion of a hyperfinite II1-factor with respect to the trace. Some properties of this measure are derived from the corresponding stochastic differential equation. Then the Taylor map is studied for a space of holomorphic functions square integrable with respect to the heat kernel measure. We also define a skeleton map from this space to a Hilbert space of holomorphic functions on a certain Cameron–Martin group. This group is a subgroup of the group of invertible elements of the II1-factor.
THE DEVELOPMENT OF A UNIQUE MANUFACTURING DEVICE TO PRODUCE A "STRING-OF-PEARLS" ANTIBIOTIC DELIVERY DEVICE FOR MASSIVE SOFT TISSUE DEFECTS
Authors: ATKINSON PATRICK , TAVAKOLI MASSOUD , ALCHIN MICHAEL , SOBICK JASON , CHEUNG GEE , LARSON BRYAN , MARTIN SIDNEY
Published: July 2002

Trauma victims suffering massive soft tissue wounds are at increased risk for infection. This is typically addressed by placing antibiotic impregnated bone cement into the tissue defect to provide a massive prophylaxis directly to the affected site. The cement–antibiotic mixture is typically "pasted" onto a length of suture by the surgeon. Unfortunately, this process is sometimes difficult to perform in the operating room environment due to difficulty in localizing the mixture on the suture. In addition, the surgeon must perform the process within a relatively short time constraint as the mixture hardens. In the current study we address this issue by proposing a unique molding design which is lightweight, cost effective, disposable, and suitable for use in the operating room environment.
SPIN-MODELS OF GRANULAR COMPACTION: FROM ONE-DIMENSIONAL MODELS TO RANDOM GRAPHS
Authors: BERG JOHANNES , MEHTA ANITA
Published: July 2002

We discuss two athermal types of dynamics suitable for spin-models designed to model repeated tapping of a granular assembly. These dynamics are applied to a range of models characterized by a 3-spin Hamiltonian aiming to capture the geometric frustration in packings of granular matter.
A Subjective Measure of Complexity
Authors: Fioretti Guido
Published: July 2002

This article presents a quantitative measure of complexity, subjectively understood as a property of the relationship between a system and its observer instead of as a property of the system itself. Within this framework, complexity is quantified by assuming to know the mental categories and the mental model by which a system is represented in the mind of its observer.

It is argued that this subjectivist concept of complexity is not in contrast with objective measures of complexity introduced in particular domains, but generalizes complexity to domains where no objective measure is feasible. An extensive numerical example is presented and thoroughly discussed.
Legally speaking
Authors: Samuelson Pamela
Published: July 2002

This column will discuss why the law has traditionally resisted characterizing information as the sort of thing that can be private property, and will speculate about why judges may be more receptive nowadays to assertions that information should be treated as property. This new attitude is illustrated by a 1987 U.S. Supreme Court decision which upheld criminal convictions based solely on the misappropriation of information which the Court found to be the property of one of the defendants' employers.
From Washington
Authors: Crawford Diane
Published: July 2002

Verbal sparring over U.S. technology policy has persisted unabated for over one decade and two presidential administrations. As politicians, academicians, and industry representatives continue to volley policy virtues, the nation has watched its strong lead in the world's technology tournament slip another few notches. Industry observers lament that setting priorities, particularly in terms of R&D spending, has reached a turning point.
Three new-generation software environments
Authors: Tyugu Enn
Published: July 2002

As a result of the Soviet computer project START, a number of intelligent software environments have been developed. In the heart of these environments lies structural program synthesis—an automatic program synthesis technique developed in the Estonian Academy of Sciences and initially implemented on old mainframe computers [4]. This program synthesis technique can be considered as a particular method of logic programming—propositional logic programming [12].
Notes from COMDEX
Authors: Press Larry
Published: July 2002

Finally, new and interesting ideas about documentation.

It is kind of funny, really. Most documentation is written by technicians—not professional writers. And most technicians would include documentation among their top ten complaints regarding the software they use. Physician, heal thyself.

This column describes ideas and suggestions from current literature on software documentation. I hope they will change the way you think about documentation. If you are in the software field, it is almost certain that you will have to write documentation, for either your peers or your users. If you are designing software, you owe it to those you serve to gain an enlightened attitude toward documentation, recognizing the interconnectedness of the software, its documentation, and the help system. Otherwise, you are not a “practical programmer.”
A dynamic hash method with signature
Authors: Cesarini F. , Soda G.
Published: July 2002

We present a dynamic external hash method that allows retrieval of a record by only one access to mass storage while maintaining a high load factor. The hash function is based on generalized spiral storage. Both primary and overflow records are allocated to the same file, and file expansion depends on being able to allocate every overflow chain to one bucket. An in-core index, built by means of a signature function, discriminates between primary and overflow records and assures one access to storage in the case of either successful or unsuccessful searching. Simulation results confirm the good expected performance.
Delivering the goods with Lisp
Authors: Barber Richard , Imlah George
Published: July 2002

Lisp has long had a reputation for the efficacy of its development environment. It is used in academia and by some R&D groups in industry; and, compared with conventional languages, it is hardly ever used in real applications in the real world. It will always be perceived as a rather arcane esoteric language if it does not successfully leave the ivory towers and start delivering the goods where it really matters—at the sharp end in industry.
Could it have been predicted?
Authors: Wilkes Maurice V.
Published: July 2002

As everyone knows, the computer industry is passing through a period of great change. I was speaking recently to a senior executive in one of the large companies vigorously working to meet the developing situation. The question he posed was: “Could it have been predicted?”
A national debate on encryption exportability
Authors: Weissman Clark
Published: July 2002

Traditionally, cryptography has been an exclusively military technology controlled by the National Security Agency (NSA). Therefore, U.S. International Traffic in Arms Regulations (ITARS) requires licenses for all export of modern cryptographic methods. Some methods, such as the Data Encryption Standard (DES), are easily obtained for export to the Coordinating Committee for Multilateral Export Controls (COCOM) countries, but not Soviet block countries, or most Third World nations.
On reasoning with the global time assumption
Authors: Singh Ambuj K.
Published: July 2002

Concurrency in distributed systems is usually modeled by a nondeterministic interleaving of atomic events. The consequences of this interleaving (or global time) assumption on the specifications and proofs of distributed programs are examined in this paper. A construction for atomic registers is presented; this construction has the surprising property that it is correct with respect to a specification based on partial orders but is incorrect with respect to a naively derived specification based on global time.
Householder reduction of linear equations
Authors: Hansen Per Brinch
Published: July 2002

This tutorial discusses Householder reduction of
n
linear equations to a triangular form which can be solved by back substitution. The main strength of the method is its unconditional numerical stability. We explain how Householder reduction can be derived from elementary-matrix algebra. The method is illustrated by a numerical example and a Pascal procedure. We assume that the reader has a general knowledge of vector and matrix algebra but is less familiar with linear transformation of a vector space.—
Author's Abstract
A high-level and flexible framework for implementing multiuser user interfaces
Authors: Dewan Prasun , Choudhary Rajiv
Published: July 2002

We have developed a high-level and flexible framework for supporting the construction of multiuser interfaces. The framework is based on a generalized editing interaction model, which allows users to view programs as active data that can be concurrently edited by multiple users. It consists of several novel components including a refinement of both the Seeheim UIMS architecture and the distributed graphics architecture that explicitly addresses multiuser interaction; the abstractions of shared active variables and interaction variables, which allow users and applications to exchange information; a set of default collaboration rules designed to keep the collaboration-awareness low in multiuser programs; and a small but powerful set of primitives for overriding these rules. The framework allows users to be dynamically added and removed from a multiuser sesssion, different users to use different user interfaces to interact with an application, the modules interacting with a particular user to execute on the local workstation, and programmers to incrementally trade automation for flexibility. We have implemented the framework as part of a system calledSuite. This paper motivates, describes, and illustrates the framework using the concrete example of Suite, discusses how it can be implemented in other kinds of systems, compares it with related work, discusses its shortcomings, and suggests directions for future work.
A method for automatic rule derivation to support semantic query optimization
Authors: Siegel Michael , Sciore Edward , Salveter Sharon
Published: July 2002

The use of inference rules to support intelligent data processing is an increasingly important tool in many areas of computer science. In database systems, rules are used in semantic query optimization as a method for reducing query processing costs. The savings is dependent on the ability of experts to supply a set of useful rules and the ability of the optimizer to quickly find the appropriate transformations generated by these rules. Unfortunately, the most useful rules are not always those that would or could be specified by an expert. This paper describes the architecture of a system having two interrelated components: a combined conventional/semantic query optimizer, and an automatic rule deriver.

Our automatic rule derivation method uses intermediate results from the optimization process to direct the search for learning new rules. Unlike a system employing only user-specified rules, a system with an automatic capability can derive rules that may be true only in the current state of the database and can modify the rule set to reflect changes in the database and its usage pattern.

This system has been implemented as an extension of the EXODUS conventional query optimizer generator. We describe the implementation, and show how semantic query optimization is an extension of conventional optimization in this context.
Single-class bounds of multi-class queuing networks
Authors: Dowdy Lawrence W. , Carlson Brian M. , Krantz Alan T. , Tripathi Satish K.
Published: July 2002

In a closed, separable, queuing network model of a computer system, the number of customer classes is an input parameter. The number of classes and the class compositions are assumptions regarding the characteristics of the system's workload. Often, the number of customer classes and their associated device demands are unknown or are unmeasurable parameters of the system. However, when the system is viewed as having a single composite customer class, the aggregate single-class parameters are more easily obtainable.

This paper addresses the error made when constructing a single-class model of a multi-class system. It is shown that the single-class model pessimistically bounds, the performance of the multi-class system. Thus, given a multi-class system, the corresponding single-class model can be constructed with the assurance that the actual system performance is better than that given by the single-class model. In the worst case, it is shown that the throughput given by the single-class model underestimates the actual multi-class throughput by, at most, 50%. Also, lower bounds are provided for the number of necessary customer classes, given observed device utilizations. This information is useful to clustering analysis techniques as well as to analysts who must obtain class-specific device demands.
Exact solution of large-scale, asymmetric traveling salesman problems
Authors: Carpaneto G. , Dell'Amico M. , Toth P.
Published: July 2002

A lowest-first, branch-and-bound algorithm for the
Asymmetric Traveling Salesman Problem
is presented. The method is based on the
Assignment Problem relaxation
and on a
subtour elimination branching scheme
. The effectiveness of the algorithm derives from reduction procedures and parametric solution of the relaxed problems associated with the nodes of the branch-decision tree. Large-size, uniformly, randomly generated instances of complete digraphs with up to 2000 vertices are solved on a DECstation 5000/240 computer in less than 3 minutes of CPU time. In addition, we solved on a PC 486/33
no wait flow shop
problems with up to 1000 jobs in less than 11 minutes and real-world
stacker crane
problems with up to 443 movements in less than 6 seconds.
Automating the design of graphical presentations of relational information
Authors: Mackinlay Jock
Published: July 2002

The goal of the research described in this paper is to develop an application-independent presentation tool that automatically designs effective graphical presentations (such as bar charts, scatter plots, and connected graphs) of relational information. Two problems are raised by this goal: The codification of graphic design criteria in a form that can be used by the presentation tool, and the generation of a wide variety of designs so that the presentation tool can accommodate a wide variety of information. The approach described in this paper is based on the view that graphical presentations are sentences of graphical languages. The graphic design issues are codified as expressiveness and effectiveness criteria for graphical languages. Expressiveness criteria determine whether a graphical language can express the desired information. Effectiveness criteria determine whether a graphical language exploits the capabilities of the output medium and the human visual system. A wide variety of designs can be systematically generated by using a composition algebra that composes a small set of primitive graphical languages. Artificial intelligence techniques are used to implement a prototype presentation tool called APT (A Presentation Tool), which is based on the composition algebra and the graphic design criteria.
Time/space tradeoffs for polygon mesh rendering
Authors: Bar-Yehuda Reuven , Gotsman Craig
Published: July 2002

We investigate architechural schemes, generalizing that of existing graphics engines, supporting fast rendering of traingle meshes. A mesh defined on
n
vertices is rendered by sending vertices down a graphics pipeline, after which they are pushed on a stack to by popped when no longer needed. Only individual traingles whose vertices are present in the stack may be rendered. The storage cost of the mesh rendering is the size of the stack required to store mesh vertices during the rendering process. This may be significantly less than
n
. The time cost of the mesh rendering is the number of vertices sent down the graphics pipeline. If a large enough stack is available, it usuffices to send each vertix once. If only a small stack is available, some vertices may have to be sent more than once, so a time/space tradeoff exists. With our architecture, stack of size O(√n) is sufficient to render any triangle mesh defined on
n
vertices, such that each vertex is sent only once through the graphics pipeline (time cost =
n
). We provide an algorithm that generates an appropriate “rendering sequence” of commands for any given mesh. Moreover, we show that no algorithm can do better, that is, Ω(√n) is a lower bound. Some
n
-vertex meshes may be rendered using a stack whose size is significantly less than O(√n). An algorithm generating a minimum-time rendering sequence rquiring the minimum stack size is an open question. We provide an approximation: if it is theoretically possible to render a triangle mesh is minimum time with a stack of size
S
, our algoithm generates a minimum-time rendering sequence requiring a stack of size no larger than 2
S
log
3/2
n
. If only a stack of size
k
is available, we provide an algorithm generating a rendering sequence requiring a stack of size no larger than
k
, such that at most
n(1+c/k)
vertices must be sent through the pipeline, for some constant
c
.
Modeling word occurrences for the compression of concordances
Authors: Bookstein A. , Klein S. T. , Raita T.
Published: July 2002

An earlier paper developed a procedure for compressing concordances, assuming that all alements occurred independently. The models introduced in that paper are extended here to take the possiblity of clustering into account. The concordance is conceptualized as a set of bitmaps, in which the bit locations reporesent documents, and the one-bits represent the occurrence of given terms. Hidden Markov Models (HMM's) are used to describe the clustering of the one-bits. However, for computational reasons, the HMM is approximated by traditional Markov models. A set of criteria is developed to constrain the allowable set of
n
-state models, and a full inventory is given for
n
≤ 4. Graph-theoretic
reduction
and
complementation
operations are defined among the various models and are used to provide a structure relating the models studied. Finally, the new methods were tested on the concordances of the English Bible and of two of the world's largest full-text retrieval systems: the Tre´sor de la Langue Franc¸aise and the Responsa Project.
The maintenance of common data in a distributed system
Authors: Awerbuch Baruch , Schulman Leonard J.
Published: July 2002

A basic task in distributed computation is the maintenance at each processor of the network, of a current and accurate copy of a common database. A primary example is the maintenance, for routing and other purposes, of a record of the current topology of the system.

Such a database must be updated in the wake of locally generated changes to its contents. Due to previous disconnections of parts of the network, a maintenance protocol may need to update processors holding widely varying versions of the database.

We provide a deterministic protocol for this problem, with only polylogarithmic overhead in both time and communication complexities. Previous deterministic solutions required polynomial overhead in at least one of these measures.
Implementing the complex arcsine and arccosine functions using exception handling
Authors: Hull T. E. , Fairgrieve Thomas F. , Tang Ping Tak Peter
Published: July 2002

We develop efficient algorithms for reliable and accurate evaluatins of the complex arcsine and arccosine functions. A tight error bound is derived for each algorithm; the results are valid for all machine-representable points in the complex plane. The algorithms are presented in a pseudocode that has a convenient exception-handling facility. Corresponding Fortran 77 programs for an IEEE environment have also been developed to illustrate the practicality of the algorithms, and these programs have been tested very carefully to help confirm the correctness of the algorithms and their error bounds. The results of these tests are included in the article, but the Fortran 77 programs are not (these programs are available from Fairgrieve). Tests of other widely available programs fail at many points in the complex plane, and otherwise are slower and produce much less accurate results.
The computation of spectral density functions for singular Sturm-Liouville problems involving simple continuous spectra
Authors: Fulton C. T. , Pruess S.
Published: July 2002

The software package SLEDGE has as one of its options the estimation of spectral density functions
p(t)
for a wide class of singular Strurm-Liouville problems. In this article the underlaying theory and implementation issues are discussed. Several examples exhibiting quite varied asymptotic behavior in
p
are presented.
Beyond the flow decomposition barrier
Authors: Goldberg Andrew V. , Rao Satish
Published: July 2002

We introduce a new approach to the maximum flow problem. This approach is based on assigning arc lengths based on the residual flow value and the residual arc capacities. Our approach leads to an
O
(min(
n
2/3
,
m
1/2
)
m
log(
n
2
/
m
) log
U
) time bound for a network with
n
vertices,
m
arcs, and integral arc capacities in the range [1, …,
U
]. This is a fundamental improvement over the previous time bounds. We also improve bounds for the Gomory-Hu tree problem, the parametric flow problem, and the approximate
s-t
cut problem.
A fourth-order-accurate Fourier method for the Helmholtz equation in three dimensions
Authors: Boisvert Ronald F.
Published: July 2002

We present fourth-order-accurate compact discretizations of the Helmholtz equation on rectangular domains in two and three dimensions with any combination of Dirichlet, Neumann, or periodic boundary conditions. The resulting systems of linear algebraic equations have the same block-tridiagonal structure as traditional central differences and hence may be solved efficiently using the Fourier method. The performance of the method for a variety of test cases, including problems with nonsmooth solutions, is presented. The method is seen to be roughly twice as fast as deferred corrections and, in many cases, results in a smaller discretization error.