bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer Simulation of Electrorheological Fluids in the Binary System of Particle Size
Authors: Mori Yasushige , Tsunamoto Tetsu , Nakayama Hitoshi
Published: July 2002

One of the typical electrorheological (ER) fluids consists of suspension of fine particles in the liquid of low dielectric constant. Particles for ER fluids generally have a size distribution, and some experimental results were reported which showed the effect of particle size on the shear stress of ER fluids. On the other hand, the simulation by dielectric polarization model concluded that the shear stress calculated did not depend on the particle size under the same volume fraction of particles. In order to understand the effect of particle size, the two dimensional computer simulation was carried out for a system containing particles of different size, by using a model similar to that reported by Klingenberg et al.

It was found that the shear stress of uniform size system did not depend on the particle size. When small and large particles, with the diameter ratio of 1:2, were mixed in equal numbers of particles, the chain-like clusters consisiting of both sizes of particles were formed. The shear stress and the response time of the binary size system were close to those of uniform size system, if the total volume fraction of particles was kept constant.
THE HEISENBERG MAGNETIC RING WITH 6 NODES: EXACT DIAGONALIZATION, BETHE ANSATZ AND STRING CONFIGURATIONS
Authors: WAL A. , LULEK T. , LULEK B. , KOZAK E.
Published: July 2002

We perform an exact diagonalization of the Heisenberg Hamiltonian for the magnetic ring consisting of N=6 nodes, compare the result with the Bethe Ansatz (BA) approach and verify the hypothesis of strings. We find and explain the failure of BA method in a single case of the highest weight eigenvector at the boundary of the Brillouin zone for the case of two spin deviations. The explanation involves the orbit structure of the corresponding set of magnetic configurations. We demonstrate that the finite size effects for N=6 only slightly deform the shape of asymptotic strings.
Electronic States and Mixing of Different Symmetry or Antiferromagnetism in Vortex Cores in dx2-y2-wave Superconductivity
Authors: OGATA MASAO
Published: July 2002

The microscopic structure of vortices in high-Tc superconductors is studied using the two-dimensional t-J model. The spatial dependences of order parameters are determined self-consistently using the Gutzwiller approximation, in which the effect of correlation is into account. In the high-doping region, the pair potential has d x2-y2-wave nature and the local density of states in the vicinity of the core shows a zero-energy peak. However, in the low-doping region, a spatially oscillating (extended) s-wave-type order parameter is locally induced around the vortex core. As a result, the local density of states near the core shows a splitting of the zero-energy peak. This gives a possible explanation for the experimental data of scanning tunneling spectroscopy for YBCO. The possibility of the antiferromagnetic vortex core is also studied by modifying the Gutzwiller approximation. It is found that, close to the boundary to the antiferromagnetically ordered state, the antiferromagnetic correlation develops inside the vortex core, even if the bulk state is the pure d-wave state. In this case the local density of states near the core does not have a zero-energy peak but instead shows a gap-like feature, which can be observed experimentally. Finally the sign change of the charge of the vortex core as a function of the doping rate is found.
Search for Superconductivity under Ultra-high Pressure
Authors: Amaya K. , Shimizu K. , Eremets M. I.
Published: July 2002

Techniques of producing ultra-high pressure at very low temperature and measuring method of electrical resistance and magnetization of samples confirmed in the used diamond anvil ceil (DAC) are shortly described. Experimental results on simple molecular systems such as iodine, sulfur, oxygen and organic iodanil are reviewed as typical example of pressure induced superconductivity.
INFLUENCE OF FIRING TEMPERATURE ON THE PROPERTIES OF CdO THIN FILMS OBTAINED BY THE SOL-GEL METHOD
Authors: ZUÑIGA-ROMERO C. I. , TORRES-DELGADO G. , JIMENEZ-SANDOVAL S. , JIMENEZ-SANDOVAL O. , CASTANEDO-PEREZ R.
Published: July 2002

CdO thin films were prepared by the sol-gel method, by using a precursor solution with cadmium acetate dihydrate as metal source. The films were obtained on slide-glass substrates and fired in open atmosphere at 200-450°C, at 50°C intervals. The X-ray data show that the films are polycrystalline with a NaCl cubic structure. The transmission of the films is 95-100% at wavelengths ≥600 nm, one of the highest obtained so far for CdO thin films. The atomic force microscopy results show that the grains coalesce, which results in morphology changes as the firing temperature increases. The resistivity showed its minimum value around 300°C (~10-3Ω-cm).
USE OF ION BEAM ANALYSIS TO STUDY IN SITU THE OXYGEN DIFFUSION AND INTERFACIAL TRANSFER COEFFICIENTS IN Y1Ba2Cu3O7-x THIN FILMS
Authors: GARCÍA LÓPEZ J. , SIEJKA J , LEMAITRE Y. , MAGE J. C. , MARCILHAC B.
Published: July 2002

An experimental chamber was connected to the 2.5 MV Van de Graaff accelerator allowing in situ sample annealing at T ≤ 700° C and under pO 2 ranging from 10-8 to 1 bar. For the first time to our knowledge the 16 O (3 He ,α)15 O nuclear reaction has been employed to monitor in situ the oxygen loss and uptake in Y 1 Ba 2 Cu 3 O 7-x (YBCO) thin films as a function of oxygen pressure and temperature ( T ≤ 500° C ). The role played by the presence of carbon contamination on YBCO surface was elucidated. Using the 12 C(d,p) 13 C nuclear reaction the carbon loss was observed for T ≥ 250° C and it was associated with the oxygen loss enhancement in YBCO. It is found that in absence of carbon contamination, oxygen in-diffusion rate in YBCO is much faster than the out-diffusion rate, the later being surface reaction limited. The oxygen diffusion coefficients and the surface exchange coefficients of YBCO films have been evaluated. These results will be discussed in relation with the mechanism of high temperature YBCO thin film growth by cathodic sputtering and with the mechanism of the oxygen loss and/or uptake during the sample cooling.
ANALYTICAL CRITERIA FOR LOCAL ACTIVITY AND APPLICATIONS TO THE OREGONATOR CNN
Authors: MIN LEQUAN , CROUNSE KENNETH R. , CHUA LEON O.
Published: July 2002

This paper presents analytic criteria for local activity in one-port Cellular Nonlinear Network (CNN) cells [Chua, 1997, 1999], and gives the applications to the Oregonator CNN defined by the kinetic chemical reaction model of morphogenesis first introduced in [Field & Noyes, 1974]. Locally active domains, locally passive domains, and the edge of chaos are identified in the cell parameter space. Computer simulations of the dynamics of several Oregonator CNN's with specific selected cell parameters in the above-mentioned domains show genesis and the emergence of complexity. Furthermore, a novel phenomena is observed that "extremely high energy" is concentrated only on a few cells in the dynamic patterns of some Oregonator CNN's whose cell parameters are located in active domains; furthermore, relaxation oscillations and "transient oscillations" can exist if the cell parameters of the Oregonator CNN are located nearby or on the edge of chaos. This research illustrates once again the effectiveness of the local activity theory in choosing the system parameters for the emergence of complex patterns (static and dynamic) in a homogeneous lattice formed by coupled cells.
THE TRANSFER OF A COMMUTATOR IDENTITY IN A NIL-GENERATED ALGEBRA
Authors: KRASILNIKOV A. N. , RILEY D. M.
Published: July 2002

We show that if an associative algebra over a field of characteristic 0 is generated by its nilpotent elements and satisfies a multilinear Lie commutator identity then its adjoint group satisfies the corresponding multilinear group commutator identity.
ON SPACES OF CONNECTED GRAPHS II: RELATIONS IN THE ALGEBRA Λ
Authors: KNEISSLER JAN A.
Published: July 2002

The graded algebra Λ defined by Pierre Vogel is of general interest in the theory of finite-type invariants of knots and of 3-manifolds because it acts on spaces of connected graphs subject to relations called IHX and AS. We examine a subalgebra Λ0 that is generated by certain elements called t and xn with n≥ 3. Two families of relations in Λ0 are derived and it is shown that the dimension of Λ0 grows at most quadratically with respect to degree. Under the assumption that t is not a zero divisor in Λ0, a basis of Λ0 and an isomorphism from Λ0 to a sub-ring of Z[t,u,v] is given.
GRAVITATIONAL COLLAPSE OF SPHERICALLY SYMMETRIC PERFECT FLUID WITH KINEMATIC SELF-SIMILARITY
Authors: BRANDT C. F. C. , LIN L.-M. , DA ROCHA J. F. VILLAS , WANG A. Z.
Published: July 2002

Analytic spherically symmetric solutions of the Einstein field equations coupled with a perfect fluid and with self-similarities of the zeroth, first and second kinds, found recently by Benoit and Coley [Class. Quantum Grav.15, 2397 (1998)], are studied, and found that some of them represent gravitational collapse. When the solutions have self-similarity of the first (homothetic) kind, some of the solutions may represent critical collapse but in the sense that now the "critical" solution separates the collapse that forms black holes from the collapse that forms naked singularities. The formation of such black holes always starts with a mass gap, although the "critical" solution has homothetic self-similarity. The solutions with self-similarity of the zeroth and second kinds seem irrelevant to critical collapse. Yet, it is also found that the de Sitter solution is a particular case of the solutions with self-similarity of the zeroth kind, and that the Schwarzschild solution is a particular case of the solutions with self-similarity of the second kind with the index α=3/2.
INTERNAL BREMSSTRAHLUNG SPECTRUM OF204TlIN THE X-RAY REGION
Authors: RAGHAVENDRA M. K. , RAMASWAMY C. R.
Published: July 2002

The internal Bremsstrahlung spectrum from204Tl has been measured, using magnetic deflector method, in the X-ray region. The corrected spectral intensity is compared with the Coulomb-corrected KUB theory in the energy region of 10 to 30 keV. The good agreement between experiment and theory in this energy region, suggests that "detour effects" are negligible in the low energy region.
COMPLETE FAMILIES AND RAYLEIGH OBSTACLES
Authors: CROSTA GIOVANNI F.
Published: July 2002

Complete families in a given function space are sets of linearly independent functions, a linear combination of which can approximate any other function with arbitrarily high accuracy. Outgoing cylindrical wave functions are one such family, used to represent the scattered wave in exterior boundary value problems for the scalar Helmholtz equation in two spatial dimensions. When the incident wave is plane and the scattered wave is represented by a series of said functions, which converges up to the boundary of the obstacle, the obstacle is said to be in the Rayleigh class. One shall further distinguish between Dirichlet–Rayleigh and Neumann–Rayleigh obstacles, according to the applicable boundary condition. Discs are trivial obstacles of these classes. Ellipses of eccentricity η such that η2<1/2 were shown to be in the Dirichlet–Rayleigh class by Barantsev et al. in 1971, who used the saddle point method to asymptotically estimate the Fourier scattering coefficients. Herewith, another one parameter family of obstacles is constructed by the same method. It is also shown that the same obstacles are in the Neumann–Rayleigh class. The relevance of these results to the numerical treatment of scattering problems is briefly discussed.
NUMERICAL SIMULATION OF TRANSVERSE CURRENT MONITORING IN THE FRAM STRAIT
Authors: NAUGOLNYKH K. A. , WANG YUN-YU , SHANG E. C.
Published: July 2002

The horizontal refraction method (HRM) of transverse current acoustics monitoring in the Fram Strait environment is modeled numerically. The current profile was constructed on the basis of experimental data on the West Spitsbergen Current (WSC) structure and the complex environment of the region presented by the sound speed profiles, which were derived from the experiments. The HRM is based on the measurements of the deflection of the horizontal modal rays due to the gradient of the refraction index produced by the transverse current. The signals received by the antennas in a receiving plane perpendicular to the propagation axis have a modal phase difference in proportion to the average transverse velocity, which is due to the different orientation of the acoustical path of the current. The interesting result is that even in a strong mode coupling environment the numerically obtained phase difference is quite close to its value as calculated by adiabatic approximation. The physical reason behind this is most likely that the mode coupling impact can be canceled at the sound signal propagation along the two very close paths.
ATOMIC STRUCTURE OF A {001} SURFACE OF THE ALLOY FeRh
Authors: KIM S. , JONA F. , MARCUS P. M.
Published: July 2002

The atomic structure of a {001} surface of the ordered binary alloy FeRh (with bulk structure of the CsCl type) is studied with quantitative low energy electron diffraction. The {001} surface structure is found to be bulklike (1× 1), with the first atomic layer 100% Rh and the second 100% Fe. The first interlayer spacing is contracted by 9.8% with respect to the bulk value (1.4935Å) and the second interlayer spacing is slightly expanded by 2.4%.
A HREELS STUDY OF BENZENETHIOL ADSORPTION ON Au(111) AND Au(322)
Authors: BARNES COLIN J. , WHELAN CAROLINE M. , GREGOIRE CHANTAL , PIREAUX JEAN-JACQUES
Published: July 2002

Adsorption of benzenethiol on a Au(111)-[Formula: see text]-reconstructed surface at 300 K leads to formation of molecular long range disordered overlayers without lifting of the surface reconstruction. Absence of the S–H stretching vibration, both in and out of specular scattering geometry, along with identification of modes typical of benzene-like systems, indicates formation of a thiolate intermediate at both saturation and submonolayer coverage. Comparison of HREELS band intensities as a function of coverage in the specular direction indicates that no major coverage-dependent reorientation occurs on Au (111) . Consideration of relative band intensities, use of dipole selection rules and comparison with previous studies of benzene and benzenethiol adsorption on transition metal surfaces indicate a largely flat-lying bonding geometry at both monolayer and submonolayer coverages. In contrast, adsorption on Au(322), a surface consisting of monoatomic (100) steps separating (111) microterraces five unit cells wide, leads to formation of an ordered monolayer. The adsorbed intermediate on Au (322) is benzenethiolate at both low and high coverage. At low coverages the molecule is strongly inclined with respect to the (111) micro-terraces while at higher coverages adsorbates adopt a more flat-lying geometry. This unusual behavior may be due to coverage-dependent occupation of step and terrace sites with a strongly inclined species formed at step sites, preferentially occupied at low coverage, and a second flat-lying state becoming occupied within the monolayer. Alternatively, both step- and terrace-bound thiolate are strongly inclined at low exposures, with the two species undergoing an orientational transition beyond a critical coverage to form a more flat-lying intermediate. This study shows clear evidence for step-induced ordering of the thiolate intermediate and the ability of steps to promote a molecular reorientation.
GROWTH AND STRUCTURE OF hcp Ti FILMS ON Al(111) SURFACES
Authors: KIM Y. W. , WHITE G. A. , SHIVAPARAN N. R. , TETER M. A. , SMITH R. J.
Published: July 2002

The structure of thin Ti films grown on Al(111) surfaces at room temperature has been studied using high energy ion scattering/channeling (HEIS), X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS), low energy electron diffraction (LEED) and X-ray photoelectron diffraction (XPD). Our results show that Ti grows in the SK mode on the Al(111) surface. Ti atoms form a two-dimensional overlayer up to a deposition of about 2 ML Ti, followed by three-dimensional island growth with additional Ti deposition. The Ti islands cover the surface completely at about 12 ML of Ti deposition. XPD results show that the Ti overlayer has a well-ordered hcp Ti(0001) structure on the fcc Al(111) surface, in remarkable contrast to the fcc Ti film growth observed on Al(001) and Al(110) surfaces.
REM STUDIES OF STEP CREATION ENERGIES AND STEP–STEP INTERACTIONS ON Si(111) AND (110) VICINAL SURFACES
Authors: SUZUKI T. , MINODA H. , TANISHIRO Y. , YAGI K.
Published: July 2002

We carried out reflection electron microscope (REM) observations of equilibrium shapes of Si(111) and (110) vicinal surfaces to estimate step creation energies and step interaction coefficients. A sample with a cylindrical hole was annealed at 1050°C under AC or DC heating. We measured widths of the facet surfaces and step positions on the vicinal surfaces and estimated the ratios of the step creation energies (B) and the step interaction coefficients (g) of these surfaces. We found that repulsive step–step interaction was stronger on the (110) surfaces than on the (111) surfaces, effective repulsive step–step interactions on both surfaces annealed by DC heating were stronger than those on surfaces annealed by AC heating, and the DC heating effect appeared more strongly on the (111) surfaces than on the (110) surfaces.
Biomechanical Analysis of Tendon Suture Techniques
Authors: Lee Kwang Suk , Woo Kyung Jo , Jeon Jae Young
Published: July 2002

The relative strength of three suture methods of lacerated tendon were measured by mechanical disruption in effort to determine the strength of suture technique.

Fifty-four calcaneal tendons of 27 New Zealand white rabbits were transected at mid-portion and repaired with the three suture techniques: group 1: Kessler suture; group 2: Pennington's modified-Kessler suture; and group 3: augmented-Becker suture technique. Each group was composed of 18 calcaneal tendons.

Three groups of rabbits, 9 in each, were, respectively, sacrificed immediately after suture, at 2 weeks postoperatively and at 4 weeks postoperatively.

The augmented-Becker repair was strongest in tensile strength and maximum stress at immediate operation, 2 weeks postoperatively and 4 weeks postoperatively.

The augmented-Becker repair had the highest modulus of elasticity at time of suture, at 2 and at 4 weeks postoperatively. Tensile strength, maximum stress and modulus of elasticity gradually increased from the time of operation to 4 weeks, but the difference was not of statistical significance at 4 weeks.
FINGER RECONSTRUCTION WITH VOLAR ADVANCEMENT FLAP USING V-Y CLOSURE
Authors: Murata K. , Yajima H. , Fujiki J. , Yoshimoto S. , Tamai S.
Published: July 2002

A variety of flaps have been reported for the reconstruction of finger tip injuries. The volar advancement flap was first intoduced in 1964. Recently, this technique was combined with V-Y closure and has been applied in the treatment of thumb tip injuries. We treated seven thumb-tip injuries and five finger-tip injuries using the volar advancement flap with V-Y closure. The flaps were advanced an average of 14 mm (range: 10 to 18 mm). All flaps survived completely. The static two-point discrimination in the flaps ranged from 5 to 8 mm (average 6.3 mm). One of the advantages of this procedure is the single-stage reconstruction of the pulp defect with preservation of sensation. In addition, skin graft coverage of the donor site is not required. The result was excellent with less postoperative complications in thumb-tip injury cases. In finger-tip injury cases, however, several postoperative complications occurred such as the PIP joint contracture, cold intolerance of the dorsum of finger tip, and claw-nail deformity. Accordingly, the indication for this flap should be limited to the thumb injury case.
HAMMING DISTANCE AND HISTORY DISTRIBUTION IN THE MINORITY GAME
Authors: D'HULST R. , RODGERS G. J.
Published: July 2002

We investigate the Minority Game, a toy model for agents buying and selling a commodity. The dynamics of the model are decomposed into two processes, firstly, an agent's choice of active strategy, secondly, the interaction between agents while they play. The latter is suitably described by the Hamming distance between strategies. Here, we argue that the first process is described by the history distribution.
TRANSACTION COSTS: A NEW POINT OF VIEW
Authors: BAVIERA ROBERTO
Published: July 2002

We consider a new point of view to portfolio selection in presence of transaction costs which allows us to map the problem into one without costs. The proposed approach connects all the quantities of interest to the average lag between two trades and the probabilities of reaching a price fluctuation of a given size. This active portfolio managing in presence of costs is based on quantities directly measurable in real markets and it leads to analytic results in the Wiener case.
COHERENT RISK MEASURES FOR DERIVATIVES UNDER BLACK–SCHOLES ECONOMY
Authors: YANG H. , SIU T. K.
Published: July 2002

This paper proposes a risk measure for a portfolio of European-style derivative securities over a fixed time horizon under the Black–Scholes economy. The proposed risk measure is scenario-based along the same line as [3]. The risk measure is constructed by using the risk-neutral probability ([Formula: see text]-measure), the physical probability ([Formula: see text]-measure) and a family of subjective probability measures. The subjective probabilities are introduced by using Girsanov's theorem. In this way, we provide risk managers or regulators with the flexibility of adjusting the risk measure according to their risk preferences and subjective beliefs. The advantages of the proposed measure are that it is easy to implement and that it satisfies the four desirable properties introduced in [3], which make it a coherent risk measure. Finally, we incorporate the presence of transaction costs into our framework.
SEQUENTIAL SEMIDEFINITE PROGRAMMING FOR OPTIMIZATION OF FRAMED STRUCTURES UNDER MULTIMODAL BUCKLING CONSTRAINTS
Authors: KANNO Y. , OHSAKI M. , KATOH N.
Published: July 2002

An algorithm based on Semi-Definite Programming (SDP) formulation is proposed for optimum design of structures for specified linear buckling load factors. Optimal trusses and frames are computed by using the primal-dual interior-point method based on SDP scheme. It is well known that optimizing structures under buckling constraints is difficult because of the non-differentiability of buckling load factors for the case of multimodal solutions. The examples studied indicate that optimum designs with multiple buckling load factors can be found with no difficulty by successively solving the SDP problems.
PRESSURE DISTRIBUTION ON WHEELCHAIR CUSHIONS IN STATIC SITTING AND DURING MANUAL PROPULSION
Authors: ANDREONI GIUSEPPE , PEDOTTI ANTONIO , FERRARIN MAURIZIO
Published: July 2002

Quantification of biomechanical parameters by describing interactions between a wheelchair user and his cushion is important to prevent pressure sores in a better way and to match the needs of the subjects in terms of comfort and mobility. This paper presents the method and the results of a biomechanical analysis through the pressure maps at the body–seat interface of a antidecubitus wheelchair cushion on a group of eight patients (affected by SCI or Multiple Sclerosis) during autonomous wheelchair propulsion. In general, our results confirm that mobility is an important factor for ulcer prevention because passing from the static sitting posture to propulsion the mean pressure decreases and there is a redistribution of the load at lower pressure values. Moreover this represents a useful approach for the customized choice and adaptation of the antidecubitus aids.
COARSENING OF VORTEX RIPPLES IN SAND
Authors: KRUG JOACHIM
Published: July 2002

The coarsening of an array of vortex ripples prepared in an unstable state is discussed within the framework of a simple mass transfer model first introduced by K. H. Andersen et al. (see Ref. 1). Two scenarios for the selection of the final pattern are identified. When the initial state is homogeneous with uniform random perturbations, a unique final state is reached which depends only on the shape of the interaction function f(λ). A potential formulation of the dynamics suggests that the final wavelength is determined by a Maxwell construction applied to f(λ), but comparison with numerical simulations shows that this yields only an upper bound. In contrast, the evolution from a perfectly homogeneous state with a localized perturbation proceeds through the propagation of wavelength doubling fronts. The front speed can be predicted by standard marginal stability theory. In this case the final wavelength depends on the initial wavelength in a complicated manner which involves multiplication by powers of two and rational ratios such as 4/3.
NONLINEAR ELASTICITY AND THERMODYNAMICS OF GRANULAR MATERIALS
Authors: MAKSE HERNÁN A.
Published: July 2002

The elastic properties of granular materials can be enormously nonlinear as compared with the properties of non-porous materials. Experiments on isotropic compression of a granular assembly of spheres show that the shear μ, and bulk k, moduli vary with the confining pressure faster than the 1/3 power law predicted by Hertz–Mindlin elasticity theory. Moreover, the ratio between the experimental bulk and shear moduli is found to be constant but with a value larger than the theoretical prediction. Numerical simulations resolve the question as to whether the problem lies with the treatment of the grain-grain contact or with the elastic framework. We find that the problem lies principally with the latter; the affine assumption (which underlies the elastic formulation) is found to be valid for k but to breakdown seriously for μ. This explains why the experimental and numerical values of μ(p) are much smaller than the elastic predictions. In this paper we review recent progress on the understanding of this problem based on microscopic simulations, elasticity theory and more innovative ideas such as jamming, fragility and thermodynamics of granular materials.
ENTROPIC ANALYSIS OF THE ROLE OF WORDS IN LITERARY TEXTS
Authors: MONTEMURRO MARCELO A. , ZANETTE DAMIÁN H.
Published: July 2002

Beyond the local constraints imposed by grammar, words concatenated in long sequences carrying a complex message show statistical regularities that may reflect their linguistic role in the message. In this paper, we perform a systematic statistical analysis of the use of words in literary English corpora. We show that there is a quantitative relation between the role of content words in literary English and the Shannon information entropy defined over an appropriate probability distribution. Without assuming any previous knowledge about the syntactic structure of language, we are able to cluster certain groups of words according to their specific role in the text.
Syntactical characterization of a subset of domain-independent formulas
Authors: Demolombe Robert
Published: July 2002

A domain-independent formula of first-order predicate calculus is a formula whose evaluation in a given interpretation does not change when we add a new constant to the interpretation domain. The formulas used to express queries, integrity constraints or deductive rules in the database field that have an intuitive meaning are domain independent. That is the reason why this class is of great interest in practice. Unfortunately, this class is not decidable, and the problem is to characterize new subclasses, as large as possible, which are decidable. A syntactic characterization of a class of formulas, the Evaluable formulas, which are proved to be domain independent are provided. This class is defined only for function-free formulas. It is also proved that the class of evaluable formulas contains the other classes of syntactically characterized domain-independent formulas usually found in the literature, namely, range-separable formulas and range-restricted formulas. Finally, it is shown that the expressive power of evaluable formulas is the same as that of domain-independent formulas. That is, each domain-independent formula admits an equivalent evaluable one. An important advantage of this characterization is that, to check if a formula is evaluable, it is not necessary to transform it to a normal form, as is the case for range-restricted formulas.
Semantic data modeling of hypermedia associations
Authors: Schnase John L. , Leggett John J. , Hicks David L. , Szabo Ron L.
Published: July 2002

Many important issues in the design and implementation of hypermedia system functionality focus on the way interobject connections are represented, manipulated, and stored. A prototypic system called HB1 is being designed to meet the storage needs of next-generation hypermedia system architectures. HB1 is referred to as a hyperbase management system (HBMS) because it supports, not only the storage and manipulation of information, but the storage and manipulation of the connectivity data that link information together to form hypermedia. Among HB1's distinctions is its use of a semantic network database system to manage physical storage. Here, basic semantic modeling concepts as they apply to hypermedia systems are reviewed, and experiences using a semantic database system in HB1 are discussed.

Semantic data models attempt to provide more powerful mechanisms for structuring objects than are provided by traditional approaches. In HB1, it was necessary to abstract interobject connectivity, behaviors, and information for hypermedia. Building on top of a semantic database system facilitated such a separation and made the structural aspects of hypermedia conveniently accessible to manipulation. This becomes particularly important in the implementation of structure-related operations such as structural queries. Our experience suggests that an integrated semantic object-oriented database paradigm appears to be superior to purely relational, semantic, or object-oriented methodologies for representing the structurally complex interrelationships that arise in hypermedia.
Phone-based CSCW
Authors: Resnick Paul
Published: July 2002

Telephones are the most ubiquitous, best-networked, and simplest computer terminals available today. They have been used for voice mail but largely overlooked as a platform for asynchronous cooperative-work applications such as event calendars, issue discussions, and question-and-answer gathering. HyperVoice is a software toolkit for constructing such applications. Its building blocks are high-level presentation formats for collections of structured voice messages. The presentation formats can themselves be presented and manipulated, enabling significant customization of applications by phone. Results of two field trials suggest social-context factors that will influence the success or failure of phone-based cooperative work applications in particular settings.
The ethical and legal quandary of email privacy
Authors: Sipior Janice C. , Ward Burke T.
Published: July 2002

What should conscientious employees and their ethical employers expect? It's hard to say.
TROLL
Authors: Jungclaus Ralf , Saake Gunter , Hartmann Thorsten , Sernadas Cristina
Published: July 2002

TROLL is a language particularly suited for the early stages of information system development, when the universe of discourse must be described. In TROLL the descriptions of the static and dynamic aspects of entities are integrated into object descriptions. Sublanguages for data terms, for first-order and temporal assertions, and for processes, are used to describe respectively the static properties, the behavior, and the evolution over time of objects. TROLL organizes system design through object-orientation and the support of abstractions such as classification, specialization, roles, and aggregation. Language features for state interactions and dependencies among components support the composition of the system from smaller modules, as does the facility of defining interfaces on top of object descriptions.
An inverted taxonomy of sorting algorithms
Authors: Merritt Susan M.
Published: July 2002

An alternative taxonomy (to that of Knuth and others) of sorting algorithms is proposed. It emerges naturally out of a top-down approach to the derivation of sorting algorithms. Work done in automatic program synthesis has produced interesting results about sorting algorithms that suggest this approach. In particular, all sorts are divided into two categories: hardsplit/easyjoin and easysplit/hardjoin. Quicksort and merge sort, respectively, are the canonical examples in these categories. Insertion sort and selection sort are seen to be instances of merge sort and quicksort, respectively, and sinking sort and bubble sort are in-place versions of insertion sort and selection sort. Such an organization introduces new insights into the connections and symmetries among sorting algorithms, and is based on a higher level, more abstract, and conceptually simple basis. It is proposed as an alternative way of understanding, describing, and teaching sorting algorithms.
Using value prediction to increase the power of speculative execution hardware
Authors: Gabbay Freddy , Mendelson Avi
Published: July 2002

This article presents an experimental and analytical study of value prediction and its impact on speculative execution in superscalar microprocessors. Value prediction is a new paradigm that suggests predicting outcome values of operations (at run-time ) and using these predicted values to trigger the execution of true-data-dependent operations speculatively. As a result, stals to memory locations can be reduced and the amount of instruction-level parallelism can be extended beyond the limits of the program's dataflow graph. This article examines the characteristics of the value prediction concept from two perspectives: (1) the related phenomena that are reflected in the nature of computer programs and (2) the significance of these phenomena to boosting instruction-level parallelism of superscalar microprocessors that support speculative execution. In order to better understand these characteristics, our work combines both analytical and experimental studies.
Jagged edges
Authors: Naiman Avi C.
Published: July 2002

Depiction of oblique edges by discrete pixels usually results in visible stair steps, often called
jaggies
. A variety of filtering approaches exists to minimize this visual artifact, but none has been applied selectively only to those edges that would otherwise appear jagged. A recent series of experiments has led to a model of the visibility of jagged edges. Here, we demonstrate how these data can be used efficiently to determine when filtering of edges is needed to eliminate the jaggies and when it is unnecessary. This work also provides a template for how the results of psychophysical experiments can be applied in computer graphics to address image-quality questions.
Complex fans
Authors: Flores Juan
Published: July 2002

If we allow the magnitude and angle of a complex number (expressed in polar form) to range over an interval, it describes a semicircular region, similar to a fan; these regions are what we call complex fans. Complex numbers are a special case of complex fans, where the magnitude and angle are point intervals. Operations (especially addition) with complex numbers in polar form are complicated. What most applications do is to convert them to rectangular form, perform operations, and return the result to polar form. However, if the complex number is a Complex Fan, that transformation increases ambiguity in the result. That is, the resulting Fan is not the smallest Fan that contains all possible results. The need for minimal results took us to develop algorithms to perform the basic arithmetic operations with complex fans, ensuring the result will always be the smallest possible complex fan. We have developed the arithmetic operations of addition, negation, subtraction, product, and division of complex fans. The algorithms presented in this article are written in pseudocode, and the programs in Common Lisp, making use of CLOS (Common Lisp Object System). Translation to any other high-level programming language should be straightforward.
Ace
Authors: Raghavachari Mukund , Rogers Anne
Published: July 2002

Customizing the protocols that manage accesses to different data structures within an application can improve the performance of software shared-memory programs substantially. Existing systems for using customizable protocols are hard to use directly because the mechanisms they provide for manipulating protocols are low-level ones. This article is an in-depth study of the issues involved in providing language support for application-specific protocols. We describe the design and implementation of a new language for parallel programming, Ace, that integrates support for customizable protocols with minimal extensions to C. Ace applications are developed using a shared-memory model with a default sequentially consistent protocol. Performance can then be optimized, with minor modifications to the application, by experimenting with different protocol libraries. The design of Ace was driven by a detailed study of the use of customizable protocols. We delineate the issues that arise when programming with customizable protocols and present novel abstractions that allow for their easy use. We describe the design and implementation of a runtime system and compiler for Ace nd discuss compiler optimizations that improve the performance of such software shared-memory systems. We study the communication patterns of a set of benchmark applications and consider the use of customizable protocols to optimize their performance. We evaluate the performance of our system through experiments on a Thinking Machine CM-5 and a Cray T3E. We also present measurements that demonstrate that Ace has good performance compared to that of a modern distributed shared-memory system.
Location of the Maximum on Unimodal Surfaces
Authors: Newman D. J.
Published: July 2002

Pinning down the maximum of a function in one or more variable is a basic computing problem. Without further a priori information regarding the nature of the function, of course, the problem is not feasible for computation. Thus if the function is permitted to oscillate infinitely often then no number of evaluations can give information regarding its maximum.

J. Kiefer, in his paper, treats the one-dimensional problem and shows that the correct a priori assumption regarding the function is that of “unimodality.” He then gives the complete and exact optimal procedure within this framework.

In this paper is given what the author believes is the correct a priori background for functions of several variables. (This is analogous to unimodality in one dimension.) However, there is not obtained the exactness of Kiefer's result, but rather the determination of the correct procedures to within “order of magnitude.”
Exact and Approximate Algorithms for Scheduling Nonidentical Processors
Authors: Horowitz Ellis , Sahni Sartaj
Published: July 2002

Exact and approximate algorithms are presented for scheduling independent tasks in a multiprocessor environment in which the processors have different speeds. Dynamic programming type algorithms are presented which minimize finish time and weighted mean flow time on two processors. The generalization to
m
processors is direct. These algorithms have a worst-case complexity which is exponential in the number of tasks. Therefore approximation algorithms of low polynomial complexity are also obtained for the above problems. These algorithms are guaranteed to obtain solutions that are close to the optimal. For the case of minimizing mean flow time on
m
-processors an algorithm is given whose complexity is O(
n
log
mn
).
Fault classes and error detection capability of specification-based testing
Authors: Kuhn D. Richard
Published: July 2002

Some varieties of specification-based testing rely upon methods for generating test cases from predicates in a software specification. These methods derive various test conditions from logic expressions, with the aim of detecting different types of faults. Some authors have presented empirical results on the ability of specification-based test generation methods to detect failures. This article describes a method for cokmputing the conditions that must be covered by a test set for the test set to guarantee detection of the particular fault class. It is shown that there is a coverage hierarchy to fault classes that is consistent with, and may therefore explain, experimental results on fault-based testing. The method is also shown to be effective for computing MCDC-adequate tests.
Logics with counting and local properties
Authors: Libkin Leonid
Published: July 2002

The expressive power of first-order logic over finite structures is limited in two ways: it lacks a recursion mechanism, and it cannot count. Overcoming the first limitation has been a subject of extensive study. A number of fixpoint logics have been introduced. and shown to be subsumed by an infinitary logic L
ω
∞ω
. This logic is easier to analyze than fixpoint logics, and it still lacks counting power, as it has a 0-1 law. On the counting side, there is no analog of L
ω
∞ω
. There are a number of logics with counting power, usually introduced via generalized quantifiers. Most known expressivityy bounds are based on the fact that counting extensions of first-order logic preserve the locality properties. This article has three main goals. First, we introduce a new logic L
*
∞ω
(
C
) that plays the same role for counting as L
ω
∞ω
does for recursion—it subsumes a number of extensions of first-order logic with counting, and has nice properties that make it easy to study. Second, we give simple direct proof that L
ω
∞ω
(
C
) expresses only local properties: those that depend on the properties of small neighborhoods, but cannot grasp a structure as a whole. This is a general way of saying that a logic lacks a recursion mechanism. Third, we consider a finer analysis of locality of counting logics. In particular, we address the question of how local a logic is, that is, how big are those neighborhoods that local properties depend on. We get a uniform answer for a variety of logics between first-order and L
*
∞ω
(
C
). This is done by introducing a new form of locality that captures the tightest condition that the duplicator needs to maintain in order to win a game. We also use this technique to give bounds on outputs of L
*
∞ω
(C)-definable queries.
Rational Chebyshev approximations to the Bessel function integrals

Ki
s
(x)
Authors: Gargantini I. , Pomentale T.
Published: July 2002

The second Remes algorithm is used to approximate the integrals

Ki
s

by rational functions. The related coefficients for the approximations of
Ki
1
,
Ki
2
,
Ki
3
are given for different precisions.
Scalable multicast security with dynamic recipient groups
Authors: Molva Refik , Pannetrat Alain
Published: July 2002

In this article we propose a new framework for multicast security based on distributed computation of security transforms by intermediate nodes. The involvement of intermediate nodes in the security process causes a new type of dependency between group membership and the topology of the multicast network. Thanks to this dependency, the containment of security exposures in large multicast groups is ensured. The framework also ensures both the scalability for large dynamic groups and the security of individual members. Two different key distribution protocols complying with the framework are introduced: an extension of the EIGamal encryption scheme, and one based on a multiexponent version of RSA.
A simple guide to five normal forms in relational database theory
Authors: Kent William
Published: July 2002

The concepts behind the five principal normal forms in relational database theory are presented in simple terms.
Audit considerations in distributed processing systems
Authors: Hansen James V.
Published: July 2002

Applications of distributed processing networks are proliferating rapidly. It is expected that by the year 2000, distributed networks will be one of the most significant developments to evolve from the computer revolution.

Distributed networks are unique in that they bring together concepts of communication, engineering, and computing. From an audit standpoint, the complexities involved in control design and testing are challenging. The auditor needs to be knowledgeable concerning these complexities in order to apply the proper audit tools, particularly since some of these tools are in need of improvement or development. This paper provides a summary of important areas of audit concern in distributed processing systems
.
An interference matching technique for inducing abstractions
Authors: Hayes-Roth Frederick , McDermott John
Published: July 2002

A method for inducing knowledge by abstraction from a sequence of training examples is described. The proposed method, interference matching, induces abstractions by finding relational properties common to two or more exemplars. Three tasks solved by a program that uses an interference-matching algorithm are presented. Several problems concerning the description of the training examples and the adequacy of interference matching are discussed, and directions for future research are considered.
An application of heuristic search methods to edge and contour detection
Authors: Martelli Alberto
Published: July 2002

This paper presents a method for detecting edges and contours in noisy pictures. The properties of an edge are embedded in a figure of merit and the edge detection problem becomes the problem of minimizing the given figure of merit. This problem can be represented as a shortest path problem on a graph and can be solved using well-known graph search algorithms. The relations between this representation of the minimization problem and a dynamic programming approach are discussed, showing that the graph search method can lead to substantial improvements in computing time. Moreover, if heuristic search methods are used, the computing time will depend on the amount of noise in the picture. Some experimental results are given; these show how various information about the shape of the contour of an object can be embedded in the figure of merit, thus allowing the extraction of contours from noisy pictures and the separation of touching objects.
Reduction of a band-symmetric generalized eigenvalue problem
Authors: Crawford C. R.
Published: July 2002

An algorithm is described for reducing the generalized eigenvalue problem
Ax
= λ
Bx
to an ordinary problem, in case
A
and
B
are symmetric band matrices with
B
positive definite. If
n
is the order of the matrix and
m
the bandwidth, the matrices
A
and
B
are partitioned into
m
-by-
m
blocks; and the algorithm is described in terms of these blocks. The algorithm reduces the generalized problem to an ordinary eigenvalue problem for a symmetric band matrix
C
whose bandwidth is the same as
A
and
B
. The algorithm is similar to those of Rutishauser and Schwartz for the reduction of symmetric matrices to band form. The calculation of
C
requires order
n
2
m
operation. The round-off error in the calculation of
C
is of the same order as the sum of the errors at each of the
n
/
m
steps of the algorithm, the latter errors being largely determined by the condition of
B
with respect to inversion.