bluuebunny/crossref_metadata_2025 huggingface dataset:
UPTAKE OF LIGHT ELEMENTS IN THIN METALLIC FILMS
Authors: MARKWITZ ANDREAS , WALDSCHMIDT MATHIAS
Published: July 2002

Ion beam analysis was used to investigate the influence of substrate temperature on the inclusion of impurities during the deposition process of thin metallic single and double layers. Thin layers of gold and aluminium were deposited at different temperatures onto thin copper layers evaporated on silicon wafer substrates. The uptake of oxygen in the layers was measured using the highly sensitive non-resonant reaction 16 O(d,p) 170 O at 920 keV. Nuclear reaction analysis was also used to probe for carbon and nitrogen with a limit of detection better than 20 ppm. Hydrogen depth profiles were measured using elastic recoil detection on the nanometer scale. Rutherford backscattering spectroscopy was used to determine the depth profiles of the metallic layers and to study diffusion processes. The combined ion beam analyses revealed an uptake of oxygen in the layers depending on the different metallic cap layers and the deposition temperature. Lowest oxygen values were measured for the Au/Cu layers, whereas the highest amount of oxygen was measured in Al/Cu layers deposited at 300°C. It was also found that with single copper layers produced at various temperatures, oxygen contamination occurred during the evaporation process and not afterwards, for example, as a consequence of the storage of the films under normal conditions for several days. Hydrogen, carbon, and nitrogen were found as impurities in the single and double layered metallic films, a finding that is in agreement with the measured oxidation behaviour of the metallic films.
Phase-Space Picture of Squeezing via Driven Generalized Parametric Oscillator
Authors: Baskoutas S. , Schommers W.
Published: July 2002

In the present work we study the phase space picture of squeezing using the model of the driven generalized parametric oscillator. Exploiting the SU (1, 1)⊕ h (4) algebraic structure of the Wigner operator we find the exact solution of the time dependent Wigner equation as well as the variances of the operators q and p. Due to the fact that we have not any violation of the Liouville's theorem, this model is appropriate to study pure quantum effects (for instance tunneling time) with the classical trajectory molecular dynamics technique.
PHOTOLUMINESCENCE STUDIES IN CuInxGa1-xSe2 FILMS PREPARED BY GRAPHITE BOX ANNEALING OF In/Ga/Cu/Se STACKED ELEMENTAL LAYERS
Authors: KUNDU S. N. , CHAUDHURI S. , PAL A. K.
Published: July 2002

CuIn x Ga 1-x Se 2 films were synthesized by graphite box annealing of In/Ga/Cu/Se stacked elemental layers deposited by thermal evaporation onto sodalime glass substrates. Photoluminescence (PL) studies were carried out in near stoichiometric and copper-rich films with Ga/(In+Ga) ratios varying between 0.24–0.29. The PL spectra were dominated by peaks at ~1.19 eV and 0.87 eV with a shoulder at ~0.84 eV. There was also a peak around 1.3 eV which could be assigned to the absorption from the split-off band. The transitions at ~1.19 eV and 0.87 eV were due to excitonic transition and donor-acceptor pair formation respectively.
FAST AND SLOW PROCESSES IN ANOMALOUS DIFFUSION
Authors: BERSHADSKII A.
Published: July 2002

Using a toy model of anomalous diffusion (for which probability distribution P(r, t) is available in analytic form), it is shown that separation between fast and slow processes in anomalous diffusion using rescaling ζ=r/1/2 in the probability distribution can lead to a pseudo-asymptotic effect. This effect implies that in considerably long intervals of time, the probability distribution P(ζ,t), effectively, depends only on ζ. Moreover, in these intervals, P(ζ) can be fitted by stretched exponential representation P(ζ)~ exp -[cζγ], where exponent γ is different from real large time asymptotic γ∞. Actually, the exponent γ depends on time and, very slowly, approaches the asymptotic value γ∞ with increasing time.
PREVENTING MULTIPLE SWITCHINGS IN POWER ELECTRONIC CIRCUITS: EFFECTS OF THE LATCH ON THE NONLINEAR DYNAMICS OF THE DC–DC BUCK CONVERTER
Authors: MYLES SALLY , DI BERNARDO MARIO
Published: July 2002

This paper investigates the effects of the insertion of a flip–flop type "latch" on the dynamics exhibited by a class of power electronic circuits. It is shown that, despite preventing multiple-switching phenomena, this device does not cause the expected suppression of chaotic behavior but actually introduces novel destabilizing effects which make the occurrence of chaos in this system to take place on a larger scale. A detailed comparison between the dynamics of the nonlatched voltage controlled converter and the latched one is presented. Also, the implications on the existence of so-called sliding orbits and the associated bifurcation diagrams are discussed.
ADAPTIVE CONTROL OF RECURRENT TRAJECTORIES BASED ON LINEARIZATION OF POINCARÉ MAP
Authors: FRADKOV ALEXANDER , GUZENKO PETER , PAVLOV ALEXEY
Published: July 2002

The problem of adaptive output feedback control aimed at stabilization of a (periodic or chaotic) goal trajectory is considered. Advantages and drawbacks of chaos control method based on linearization of Poincaré map (first proposed by Ott, Grebogi and Yorke in 1990) are discussed. It is suggested that the recurrence of the goal trajectory is the key property for applicability of approach. Algorithms of adaptive control based on linearization of controlled Poincaré map and method of goal inequalities are proposed. It is shown that stabilization of recurrent trajectories is possible under additional controllability-like and observability-like conditions. Examples of stabilization of periodic and chaotic trajectories for forced brusselator and Rössler systems are studied by computer simulations.
STABILIZING EFFECT OF A LOCAL DEFECT ON CHAOTIC DYNAMICS
Authors: CHAU N. P. , MESTIVIER D.
Published: July 2002

Let Xi = F (Xi-1), where F is chaotic on a domain Ω of Rn. If F becomes insensitive, i.e. gives the same response, H, in an open subset of D of Ω, then F engenders locally stable periodic orbits. We discussed the relationship between F, D, H and the periods of these orbits. The idea of local defect might be of use in discussing chaos in health and disease.
SECURE DIGITAL SIGNAL TRANSMISSION BY MULTISTEP PARAMETER MODULATION AND ALTERNATIVE DRIVING OF TRANSMITTER VARIABLES
Authors: PALANIYANDI P. , LAKSHMANAN M.
Published: July 2002

The idea of secure communication of digital signals via chaos synchronization has been plagued by the possibility of attractor reconstruction by eavesdroppers as pointed out by Pérez and Cerdeira. In this Letter, we wish to present a very simple mechanism by which this problem can be overcome, wherein the signal is transmitted via a multistep parameter modulation combined with alternative driving of different transmitter variables, which makes the attractor reconstruction impossible. The method is illustrated by means of the Lorenz system and Chua's circuit as examples.
A GENERALIZED CHUA CELL FOR REALIZING ANY CONTINUOUS n-SEGMENT PIECEWISE-LINEAR FUNCTION
Authors: BUCOLO M. , FORTUNA L. , FRASCA M. , XIBILIA M. G.
Published: July 2002

In this letter it is proven that any piecewise-linear (PWL) function can be realized as the sum of a definite number of basic PWL functions, like that implemented in the classical Cellular Neural Network (CNN) structure by L. Chua. This allows us to consider the basic Chua's PWL function as a fundamental unit to build up a generic PWL function and, thus, to extend the class of nonlinear dynamics that can be realized by CNNs to a more wide class including PWL approximation of any nonlinearity. Moreover, an example of the cell realization of such a CNN is reported.
CONVECTIVE INSTABILITIES IN HOMEOTROPIC NEMATICS: PATTERNS AND DYNAMICAL EFFECTS IN NONLINEAR REGIMES
Authors: BOVE I. , SALÁN J. , FERNÁNDEZ J.
Published: July 2002

We present experimental results showing the convective patterns near to and far from the threshold in a horizontal film of Homeotropic Nematics subjected to an inverse vertical thermal gradient. Depending on the intensity of the applied external magnetic fields, two transitions are studied: square–hexagons and hexagon–square. In all cases, there is a coexistence of two kinds of pattern. The temporal evolution of structures was also observed, and so, mechanisms including this dynamic are proposed for the transitions between patterns.
SPATIOTEMPORAL STRUCTURES IN UNDOPED PHOTOEXCITED SEMICONDUCTOR SUPERLATTICES
Authors: PERALES A. , BONILLA L. L. , MOSCOSO M. , GALÁN J.
Published: July 2002

Semiconductor superlattices are a very interesting example of a nonlinear dynamical system with a large number of degrees of freedom. They show a strongly nonlinear behavior and they are well suited for the observation of current instabilities. In the present work, the dynamical behavior of undoped photoexcited superlattices has been analyzed by numerical continuation methods and bifurcation theory within the framework of a simple drift-diffusion model. The control parameters are the applied dc voltage and the carrier density, which are related to the laser power. We compile our results in a phase diagram and locate the lines where the system undergoes qualitative changes of behavior. The oscillatory regions are related to the appearance and disappearance of Hopf tongue crossings, for which oscillations appear as sub- or supercritical bifurcations. This implies the existence of voltage windows of current oscillations and hysteresis in appropriate parameter ranges, which agrees with recent experimental observations.
TANGLED SEPARATRICES ON TWO DEGREES OF FREEDOM SWING EQUATION SYSTEM
Authors: HASEGAWA YOSHITAKA , UEDA YOSHISUKE
Published: July 2002

One of the applications of two degrees of freedom swing equation system is the transient stability problem of an electrical power system. Using the Liapunov function method, there are many reports on the sufficient conditions of normal operations. However the basin structure of the stable equilibrium point, which corresponds to the normal operating state, is not entirely known. In this paper we will approach this problem by investigating the structure of the separatrix of the corresponding conservative system. This separatrix decomposes the phase space into regions of bound motions and divergent motions. This boundary concerns the invariant manifolds of the closed orbits on the center-manifolds of the saddle-center equilibrium points, which appear under the conservative condition. By numerical simulations, we will confirm in this report that there are transverse homoclinic intersections on these manifolds, whose cross-sectional view is different from a familiar homoclinic structure due to the asymmetric feature of the potential. Such circumstances are not observed, for example, on the well-known Hénon–Heiles system whose saddle-center equilibrium point has a trivial homoclinic loop.
PERIODIC ORBITS AND CHAOS IN THE CLASSICAL AND QUANTUM MECHANICS OF MOLECULAR SYSTEMS
Authors: LOSADA J. C. , ESTEBARANZ J. M. , BENITO R. M. , ARRANZ F. J. , BORONDO F.
Published: July 2002

A study on the classical-quantum correspondence in the LiNC/LiCN molecular system is presented. A resonance playing a very important role in the vibrational dynamics of this system of coupled anharmonic oscillators from both points of view has been found, and some aspects of its classical and quantum behavior discussed.
POSITIVITY OF k-EPSILON TURBULENCE MODELS FOR INCOMPRESSIBLE FLOW
Authors: WU ZI-NIU , FU SONG
Published: July 2002

The k-epsilon turbulence model for incompressible flow involves two advection–diffusion equations plus point-source terms. We propose a new method for positivity analysis. This method uses an iterative procedure combined with an operator splitting. With this method we recover the well-known positivity result for the standard high Reynolds number model. Most importantly, we are able to prove the positivity result for general low Reynolds number k-epsilon models.
AN OBJECT-ORIENTED TOOLBOX FOR ADAPTIVE NEURAL NETWORKS' IMPLEMENTATION
Authors: MANIOUDAKIS GEORGE D. , LIKOTHANASSIS SPIRIDON D.
Published: July 2002

Neural Networks are massively parallel processing systems, that require expensive and usually not available hardware, in order to be realized. Fortunately, the development of effective and accessible software, makes their simulation easy. Thus, various neural network's implementation tools exist in the market, which are oriented to the specific learning algorithm used. Furthermore, they can simulate only fixed size networks. In this work, we present some object-oriented techniques that have been used to defined some types of neuron and network objects, that can be used to realize, in a localized approach, some fast and powerful learning algorithms which combine results of the optimal filtering and the multi-model partitioning theory. Thus, one can build and implement intelligent learning algorithms that face both, the training as well as the on-line adjustment of the network size. Furthermore, the design methodology used, results to a system modeled as a collection of concurrent executable objects, making easy the parallel implementation. The whole design results in a general purpose tool box which is characterized by maintainability, reusability, and increased modularity. The provided features are shown by the presentation of some practical applications.
INVOLUTIONS ON KNOT GROUPS AND VARIETIES OF REPRESENTATIONS IN A LIE GROUP
Authors: ABDELGHANI LEILA BEN , LINES DANIEL
Published: July 2002

We prove the existence of a rationalisation [Formula: see text] of a classical or high-dimensional knot group Π which admits an involution if the Alexander polynomials of the knot are reciprocal. Using the group [Formula: see text] and its involution, we study the local structure, in the neighbourhood of an abelian representation, of the space of representation of the knot group Π in a a Lie group. We apply these results to the groups of classical prime knots up to 10 crossings.
Links with surgery yielding the 3-sphere
Authors: Teragaito Masakazu
Published: July 2002

For any n≥2, we give infinitely many unsplittable links of n components in the 3-sphere which admit non-trivial surgery yielding the 3-sphere again and whose components are mutually distinct hyperbolic knots. In particular, our links have tunnel number n-1. We can also give infinitely many 2-component hyperbolic links with such properties.
ARC INDEX OF NON-ALTERNATING LINKS
Authors: BELTRAMI ELISABETTA
Published: July 2002

We construct minimal arc presentations of some non-alternating links which are adequate and generalise the class of semi-alternating links. The construction allows us to make some remarks on arc index of mutants.
GENERALIZED HYBRID DERIVATIVE COUPLING MODEL FOR DEFORMED NUCLEI
Authors: MITRA PARNA , MALAKAR BINAY , GANGOPADHYAY G.
Published: July 2002

The generalized hybrid derivative coupling model has been applied to explore various ground state properties of a number of deformed nuclei throughout the periodic table. In this work we have confined our calculation only to the model characterized by hybridization parameter α=1/4. For the light nuclei in the sd shell, the binding energy prediction is reasonably good while the results for charge radius, quadrupole moment and deformation are excellent. For the rare earth and actinide nuclei, the results in the heavier isotopes are reasonably good while the model fails in the lighter isotopes.
THE ROLE OF MEMBRANE ELECTROSTATICS IN THE REGULATION OF CELL VOLUME AND ION CONCENTRATIONS
Authors: GENET S. , COSTALAT R.
Published: July 2002

We present a model to study how membrane surface negative charges can affect the electro-osmotic regulation properties of a cell. This model is based on the cellular analog proposed by Jakobsson, which includes passive and active ion transports; we further introduce the effect of membrane surface charges, using a generalized formulation of the Gouy–Chapman theory. We derive a system of nonlinear differential-algebraic equations (DAEs) which describes the dynamics of the cellular analog. The system admits a unique asymptotically stable stationary state, in which the Na-pump rate, which is crucial for electro-osmotic regulation, is inversely related to the Ca2+level in the extracellular milieu; numerical integration shows that this apparent inhibition of the Na-pump by external Ca2+results from a decrease in the electrostatic field produced by surface charges at the external side of the membrane. Furthermore, the degree of stability of the stationary state dramatically depends on the amount of negative charges on the membrane; a maximal stability is obtained for densities around - e /500 Å2, where the Na-pump is maximally activated by an increase in the Na content of the cytoplasm.
CHEMICALLY-CONTROLLED REACTION KINETICS ON FRACTALS: APPLICATION TO HYDROGEN EXCHANGE IN LYSOZYME
Authors: DEWEY T. GREGORY
Published: July 2002

The effect of time-dependent diffusional rate constants on chemically-controlled reactions in solution is considered. A general mechanism is examined that consists of a two step process. First the reactants diffuse together to form an “encounter complex.” This is followed by the collapse of the complex to the final product. The first step is diffusion controlled and the second step is chemically controlled. For reactions in restricted geometries or on fractals the rate constants associated with the diffusive process will scale with time as t−h where h is a constant between 0 and 1. The chemical processes are assumed to have time-independent rate constants. For reactions in which the encounter complex achieves a steady state, the differential equations governing the time course of the reaction can be solved exactly. At short times, the concentration of the reactants decays exponentially, reflecting the time constant of the chemical processes. At longer times, the decreasing diffusive rate constants result in the process being diffusion controlled. A stretched exponential of the form, exp{−kt1−h}, is observed. Approximate solutions for the pre-steady state behavior of the system are also determined using a Liouville transformation and corresponding asymptotic expansions. The short time regime shows power law decays of reactants. These decays will depend both on the dimensionality of the system as well as on the value of the rate constants associated with individual steps in the mechanism. Conditions can exist where a transformation to logarithmic oscillations will occur. Using this theoretical foundation a model is developed to analyze the kinetics of hydrogen isotope exchange kinetics in proteins. The exchange reaction is assume to occur in the boundary volume of the protein. Using the predicted fractal dimension of this boundary volume, scaling exponents are calculated and used as an unadjusted parameter. Highly accurate fits to the experimental data are achieved and activation energies are obtained that reflect the energetics of isotope exchange. This approach allows chemical kinetic behavior to be predicted from X-ray structure information.
SURFACE COMPOUNDS AND REACTIONS IN RELATION TO THE RESPONSE OF SOLID STATE POTENTIOMETRIC CHEMICAL SENSORS
Authors: RADIĆ N.J. , DOBČNIK D.
Published: July 2002

Potentiometric chemical sensors (PCS's) with membranes prepared by pressing a powdered disk of a mixture of inorganic salts or by chemical treatment of metal wire are investigated. The compounds on the surface of the sensor membrane important for its response and processes occurring across the membrane-solution interface for different membranes are discussed. The models of an electrochemical cell with a PCS and equations for corresponding potentials are expressed.
DIAMOND REPLICA FILMS: A GROWTH DYNAMICS ANALYSIS
Authors: SALVADORI M. C. , PASSARO A. M. PIZZO , OATTANI M.
Published: July 2002

In this work we analyze diamond replicas fabricated with silicon molds. The diamond was deposited by the CVD technique and the silicon substrates were wet-etched to obtain the replicas. The growth dynamics of the diamond replica films were investigated by the AFM technique.
CONTROLLED AMBIENT TEMPERATURE IN THE POSTOPERATIVE MANAGEMENT OF MICRO-RECONSTRUCTIVE PROCEDURES
Authors: Chew Winston Yoon-Chong , Lim Beng-Hai , Khoo David Boo-Aun , Yong Fok-Chuan , Teoh Lam-Chuan
Published: July 2002

Following microvascular reconstructive procedures, it is beneficial to maintain a high blood flow through the vascular pedicle during the critical period as this decreases the risk of thrombosis and failure. Blood flow is dependent on perfusion pressure and vascular resistance. Changes in vascular diameter and viscosity are the main determinants of blood flow in a flap. Increase in temperature causes vasodilation and decreased viscosity, and hence increase in blood flow. The benefit of maintaining a preset constant warm ambient temperature of 34°C in the postoperative care of microvascular reconstructive procedures is achieved by using the Ambience Control Device, which is an incubator with a closed environment warmed by a servo-feedback heating mechanism. It also has the advantages of patient comfort and ease of use.
BILATERAL CONGENITAL ABSENCE OF THE FLEXOR POLLICIS LONGUS
Authors: Neal N.C. , Burke F.D.
Published: July 2002

A patient with bilateral absence of flexor pollicis longus received 2 stage tendon transfers with pulley construction strengthening both thumbs and obtaining adequate IP joint motion with improved dexterity.
CEPHALOCAUDAL VARIATIONS IN THE HORIZONTAL AND VERTICAL DIAMETERS OF THE PEDICLES OF THE LUMBAR SPINE IN THE TURKISH POPULATION
Authors: Öğün Tunç Cevat , Üstün Mehmet Erkan , Büyükmumcu Mustafa
Published: July 2002

Purpose: Racial morphometric differences in the pedicular structure of the vertebrae must be taken into account when using international transpedicular screw systems. In this study, we tried to figure out the differences, if any, in the size of the pedicles in a sample of the Turkish population. Methods: The horizontal and vertical diameters of the pedicles of the lumbar vertebrae were measured from the standardized anteroposterior radiographs of the lumbar spine in 100 subjects, aged from 20 to 40 years. Results: The mean horizontal width of the pedicles in our sample of the Turkish population was smaller than the subjects in other studies. The vertical diameter did not differ widely. There was a cephalocaudal increase in the horizontal diameters in both sexes. The vertical diameters did not increase. Significant differences between the pedicle diameters of the males and the females were noted at L2, L3 and L4 levels. No significant age-related variations were observed. Conclusion: Awareness of the racial variations in the size of the pedicles is very important when using international transpedicular screw systems. Preoperative determination of especially the horizontal diameter of the pedicles to be used for screw implantation from standardized anteroposterior X-rays is the easiest way.
FINANCIAL MODELING AND OPTION THEORY WITH THE TRUNCATED LEVY PROCESS
Authors: MATACZ ANDREW
Published: July 2002

In recent studies the truncated Levy process (TLP) has been shown to be very promising for the modeling of financial dynamics. In contrast to the Levy process, the TLP has finite moments and can account for both the previously observed excess kurtosis at short timescales, along with the slow convergence to Gaussian at longer timescales. In this paper I further test the truncated Levy paradigm using high frequency data from the Australian All Ordinaries share market index. I then consider an optimal option hedging strategy which is appropriate for the early Levy dominated regime. This is compared with the usual delta hedging approach and found to differ significantly.
CONSTRUCTION OF DIRICHLET FORMS ON STANDARD FORMS OF VON NEUMANN ALGEBRAS
Authors: PARK YONG MOON
Published: July 2002

For a von Neumann algebra ℳ acting on a Hilbert space ℋ with a cyclic and separating vector ξ0, we give an explicit expression of Dirichlet forms on the natural standard form [Formula: see text] associated with the pair (ℳ, ξ0). For any self-adjoint analytic element x of ℳ and an admissible function f, we construct a (bounded) Dirichlet form which generates a symmetric Markovian semigroup on ℋ. We then apply our result to construct translation invariant, symmetric, Markovian semigroups for quantum spin systems with finite range interactions.
GALOIS GROUPS OF FIRST ORDER THEORIES
Authors: CASANOVAS E. , LASCAR D. , PILLAY A. , ZIEGLER M.
Published: July 2002

We study the groups Gal L(T) and Gal KP(T), and the associated equivalence relations EL and EKP, attached to a first order theory T. An example is given where EL≠ EKP (a non G-compact theory). It is proved that EKP is the composition of EL and the closure of EL. Other examples are given showing this is best possible.
HIGH-FREQUENCY NOISE IN PSEUDOMORPHIC DOUBLE-HETEROJUNCTION HIGH ELECTRON MOBILITY TRANSISTORS
Authors: LONG S. , ESCOTTE L. , GRAFFEUIL J. , FELLON P. , GEIGER D. , PONS D.
Published: July 2002

The noise behavior of pseudomorphic double-heterojunction high electron mobility transistors dedicated to power applications is investigated in this paper and compared to conventional low noise field effect transistors. The noise is analyzed from an extrinsic and an intrinsic point of view. It appears that the minimum noise figure is similar for the two devices even if the intrinsic noise sources are different. We explain this phenomenon using the double-heterojunction mode of operation.
SOME EXAMPLES IN COGALOIS THEORY WITH APPLICATIONS TO ELEMENTARY FIELD ARITHMETIC
Authors: ALBU TOMA
Published: July 2002

The aim of this paper is to provide some examples in Cogalois Theory showing that the property of a field extension to be radical (resp. Kneser, or Cogalois) is not transitive and is not inherited by subextensions. Our examples refer especially to extensions of type [Formula: see text]. We also effectively calculate the Cogalois groups of these extensions. A series of applications to elementary arithmetic of fields, like:

• for what n, d ∈ ℕ* is [Formula: see text] a sum of radicals of positive rational numbers

• when is [Formula: see text] a finite sum of monomials of form [Formula: see text], where r, j1,…, jr ∈ ℕ*, c ∈ ℚ*, and [Formula: see text]

are also presented.
BIOMECHANICAL MODELING OF HUMAN MOTION WITH APPLICATIONS TO SPRINT AND DISTANCE RUNNING
Authors: KARALIS T. K.
Published: July 2002

An athlete may be near exhaustion because his muscles have depleted their supply of ATP, and oxidation and glycolysis have not yet been able to replenish the muscles with their primary source of energy.

In order that the time relations of these processes offer some practical hints, a simplified "pay-off" theory for the "best" possible way to reach a desired velocity is examined, in terms of its physical appropriateness and mathematical foundation.

The derivation of the basic equations under quite general assumptions is provided. A discussion of the physical interpretation of the state and control parameters is given, and a solution of typical simplified problems is obtained.
A FRAMEWORK FOR ACHIEVING ECO-EFFICIENCY IN NEW HOUSING DEVELOPMENTS
Authors: PETT JACQUELINE M. , VAN DER VORST RITA
Published: July 2002

The technologies for building environmentally sound homes are well known and have been demonstrated in numerous projects, but are yet to be adopted as standard in the UK. Local authority development plans now include "sustainability" within their principles, but this is applied mainly in the social context. One barrier to achieving sustainable new housing is the lack of a framework to combine the objectives and policies of the urban environment, environmental impacts, resource use, and the design and construction of the houses themselves. This paper describes a framework designed for use by decision-makers (i.e. housing developers and planning officers) to help them address one part of "sustainability", namely eco-efficiency. The theoretical framework is then applied to a case study. Both the development process and the application of the framework reveal interesting points to be considered in the progress towards sustainable housing.
A CASE STUDY ON POLICY-STRATEGIC ENVIRONMENTAL ASSESSMENT: THE ECO-AUDIT OF THE IRISH NATIONAL DEVELOPMENT PLAN 2000–2006
Authors: ZAGORIANAKOS EFTHIMIS I.
Published: July 2002

This paper, which is based on a recent research project, offers an insight into the experience of integration of Strategic EnvironmentalAssessment (SEA) within government policy-making in Ireland, and Greater Dublin in particular. This is materialised by means of appraising the degree of integration of the Eco-Audit process with the transport policy-making process of the Irish National Development Plan (2000–2006). The recent establishment of the Eco-Audit guidelines by the Irish government in 1999 is the first attempt to institutionalise a type of policy-SEA in Ireland and one of few internationally. Therefore, it can be seen as a "good practice" case study that could potentially provide the context for transference of experience on SEA integration in similar institutional settings in other countries as well in different decision-making levels within Ireland. The paper concludes that this initiative undoubtedly promotes SEA practice at a sensitive government policy level and provides useful ideas for further SEA integration in the future shaping of the Eco-Audit model.
A simple output-sensitive algorithm for hidden surface removal
Authors: Sharir Micha , Overmars Mark H.
Published: July 2002

We derive a simple output-sensitive algorithm for hidden surface removal in a collection of
n
triangles in space for which a (partial) depth order is known. If
k
is the combinatorial complexity of the output
visibility map
, the method runs in time O(n √k log n). The method is extended to work for other classes of objects as well, sometimes with even improved time bounds. For example, we obtain an algorithm that performs hidden surface removal for
n
(nonintersecting) balls in time O(n
3/2
log n + k).
On the numerical inversion of Laplace transforms
Authors: Duffy Dean G.
Published: July 2002

Three frequently used methods for numerically inverting Laplace transforms are tested on complicated transforms taken from the literature. The first method is a straightforward application of the trapezoidal rule to Bromwich's integral. The second method, developed by Weeks [22], integrates Bromwich's integral by using Laguerre polynomials. The third method, devised by Talbot [18], deforms Bromwich's contour so that the integrand of Bromwich's integral is small at the beginning and end of the contour. These methods are also applied to joint Laplace-Fourier transform problems. All three methods give satisfactory results; Talbot's, however, has an accurate method for choosing required parameters.
Algorithm 726: ORTHPOL–a package of routines for generating orthogonal polynomials and Gauss-type quadrature rules
Authors: Gautschi Walter
Published: July 2002

A collection of subroutines and examples of their uses, as well as the underlying numerical methods, are described for generating orthogonal polynomials relative to arbitrary weight functions. The object of these routines is to produce the coefficients in the three-term recurrence relation satisfied by the orthogonal polynomials. Once these are known, additional data can be generated, such as zeros of orthogonal polynomials and Gauss-type quadrature rules, for which routines are also provided.
Interactive proofs and the hardness of approximating cliques
Authors: Feige Uriel , Goldwasser Shafi , Lovász Laszlo , Safra Shmuel , Szegedy Mario
Published: July 2002

The contribution of this paper is two-fold. First, a connection is established between approximating the size of the largest clique in a graph and multi-prover interactive proofs. Second, an efficient multi-prover interactive proof for NP languages is constructed, where the verifier uses very few random bits and communication bits. Last, the connection between cliques and efficient multi-prover interaction proofs, is shown to yield hardness results on the complexity of approximating the size of the largest clique in a graph.

Of independent interest is our proof of correctness for the multilinearity test of functions.
The temporal query language TQuel
Authors: Snodgrass Richard
Published: July 2002

Recently, attention has been focused on
temporal databases
, representing an enterprise over time. We have developed a new language,
Tquel
, to query a temporal database. TQuel was designed to be a minimal extension, both syntactically and semantically, of Quel, the query language in the Ingres relational database management system. This paper discusses the language informally, then provides a tuple relational calculus semantics for the TQuel statements that differ from their Quel counterparts, including the modification statements. The three additional temporal constructs defined in Tquel are shown to be direct semantic analogues of Quel's where clause and target list. We also discuss reducibility of the semantics to Quel's semantics when applied to a static database. TQuel is compared with ten other query languages supporting time.
Parallel execution for serial simulators
Authors: Nicol David , Heidelberger Philip
Published: July 2002

This article describes an approach to discrete event simulation modeling that appears to be effective for developing portable and efficient parallel execution of models of large distributed systems and communication networks. In this approach, the modeler develops submodels with an existing sequential simulation modeling tool, using the full expressive power of the tool. A set of modeling language extensions permits automatically sychronized communication between submodels; however, the automation requires that any such communication must take a nonzero amount of simulation time. Within this modeling paradigm, a variety of conservative synchronization protocols can transparently support conservative execution of submodels on potentially different processors. A specific implementation of this approach, U.P.S. (Utilitarian Parallel Simulator), is described, along with performance results on the Intel Paragon and on the IBM SP2.
Lossless compression of computer generated animation frames
Authors: Yun Hee Cheol , Guenter Brian K. , Mersereau Russell M.
Published: July 2002

This article presents a new lossless compression algorithm for computer animation image sequences. The algorithm uses transformation information available in the animation script and floating point depth and object number information at each pixel to perform highly accurate motion prediction with vary low computation. The geometric data (i.e., the depth and object number) can either be computed during the original rendering process and stored with the image or computed on the fly during compression and decompression. In the former case the stored geometric data are very efficientlycomporessed using motion prediction and a new technique called direction coding, typically to 1 to 2 bits per pixel. The geometric data are also useful in z-buffer image compsiting and this new compression algorthm offers a very low storage overhead method for saving the information needed for this comoositing. The overall compression ratio of the new algorithm, including the geometic data overhead, in compared to conventional spatial linear prediction compression and block-matching motion. The algorithm improves on a previous motion prediction algorithm by incorporating block predictor switching and color ratio predition. The combination of thes techniques gives compression ratios 30% better than those reported previously.
Drawing graphs to convey proximity
Authors: Cohen Jonathan D.
Published: July 2002

Graph drawings are increasingly finding their way into user interfaces to convey a variety of relationships. This article deals with rendering graphs to show proximity between vertices by making their configuration (screen) distances reflect their distances in the graph. An arrangement method is described that achieves good drawings at speeds suitable for user interaction on a desktop computer. The method is “incremental” in that it first arranges a small portion of the graph, then arranges successively larger fractions of the graph until a suitable arrangement for the entirety is achieved. The incremental approach not only offers speed improvements, but avoids many of the suboptimal solutions reached with other iterative approaches. Algorithms are described in pseudocode, and results are presented.
Applications of a logic of knowledge to motion planning under uncertainty
Authors: Brafman Ronen I. , Latombe Jean-Claude , Moses Yoram , Shoham Yoav
Published: July 2002

Inspired by the success of the distributed computing community in apply logics of knowledge and time to reasoning about distributed protocols, we aim for a similarly powerful and high-level abstraction when reasoning about control problems involving uncertainty. This paper concentrates on robot motion planning with uncertainty in both control and sensing, a problem that has already been well studied within the robotics community. First, a new and natural problem in this domain is defined: does there exists a sound and complete termination condition for a motion, given initial and goal locations? If yes, how to construct it? Then we define a high-level language, a logic of time and knowledge, which we use to reason about termination conditions and to state general conditions for the existence of sound and complete termination conditions in a broad domain. Finally, we show that sound termination conditions that are optimal in a precise sense provide a natural example of knowledge-based programs with multiple implementations.
A specification language for direct-manipulation user interfaces
Authors: Jacob Robert J. K.
Published: July 2002

A direct-manipulation user interface presents a set of visual representations on a display and a repertoire of manipulations that can be performed on any of them. Such representations might include screen buttons, scroll bars, spreadsheet cells, or flowchart boxes. Interaction techniques of this kind were first seen in interactive graphics systems; they are now proving effective in user interfaces for applications that are not inherently graphical. Although they are often easy to learn and use, these interfaces are also typically difficult to specify and program clearly.

Examination of direct-manipulation interfaces reveals that they have a coroutine-like structure and, despite their surface appearance, a peculiar, highly moded dialogue. This paper introduces a specification technique for direct-manipulation interfaces based on these observations. In it, each locus of dialogue is described as a separate object with a single-thread state diagram, which can be suspended and resumed, but retains state. The objects are then combined to define the overall user interface as a set of coroutines, rather than inappropriately as a single highly regular state transition diagram. An inheritance mechanism for the interaction objects is provided to avoid repetitiveness in the specifications. A prototype implementation of a user-interface management system based on this approach is described, and example specifications are given.
A comparative analysis of methodologies for database schema integration
Authors: Batini C. , Lenzerini M. , Navathe S. B.
Published: July 2002

One of the fundamental principles of the database approach is that a database allows a nonredundant, unified representation of all data managed in an organization. This is achieved only when methodologies are available to support integration across organizational and application boundaries.

Methodologies for database design usually perform the design activity by separately producing several schemas, representing parts of the application, which are subsequently merged. Database schema integration is the activity of integrating the schemas of existing or proposed databases into a global, unified schema.

The aim of the paper is to provide first a unifying framework for the problem of schema integration, then a comparative review of the work done thus far in this area. Such a framework, with the associated analysis of the existing approaches, provides a basis for identifying strengths and weaknesses of individual methodologies, as well as general guidelines for future improvements and extensions.
A knowledge-based message management system
Authors: Chang Shi-Huo , Leung L.
Published: July 2002

The design approach of a knowledge-based message management system is described. A linguistic message filter is used to filter out junk messages. Relevant messages are then processed by an expert system, driven by user-defined alerter rules. An alerter rule base for a secretarial office is illustrated. Further research topics in knowledge-base design, evaluation, and learning are also discussed.
Feedback vertex sets and cyclically reducible graphs
Authors: Wang Ching-Chy , Lloyd Errol L. , Soffa Mary Lou
Published: July 2002

The problem of finding a minimum cardinality feedback vertex set of a directed graph is considered. Of the classic NP-complete problems, this is one of the least understood. Although Karp showed the general problem to be NP-complete, a linear algorithm for its solution on reducible flow graphs was given by Shamir. The class of reducible flow graphs is the only nontrivial class of graphs for which a polynomial-time algorithm to solve this problem is known. The main result of this paper is to present a new class of graphs—the
cyclically reducible graphs
—for which minimum feedback vertex sets can be found in polynomial time. This class is not restricted to flow graphs, and most small graphs (10 or fewer nodes) fall into this class. The identification of this class is particularly important since there do not exist approximation algorithms for this problem having a provably good worst case performance. Along with the class and a simple polynomial-time algorithm for finding minimum feedback vertex sets of graphs in the class, several related results are presented. It is shown that there is no “forbidden subgraph” characterization of the class and that there is no particular inclusion relationship between this class and the reducible flow graphs. In addition, it is shown that a class of (general) graphs, which are related to the reducible flow graphs, are contained in the cyclically reducible class.
Rotating virtual objects with real handles
Authors: Ware Colin , Rose Jeff
Published: July 2002

Times for virtual object rotations reported in the literature are of the order of 10 seconds or more and this is far longer than it takes to manually orient a “real” object, such as a cup. This is a report of a series of experiments designed to investigate the reasons for this difference and to help design interfaces for object manipulation. The results suggest that two major factors are important. Having the hand physically in the same location as the virtual object being manipulated is one. The other is based on whether the object is being rotatted to a new, randomly determined orientation, or is always rotated to the same position. Making the object held in the hand have the same physical shape as the object being visually manipulated was not found to be a significant factor. The results are discussed in the context of interactive virtual environments.
Concurrency control in a system for distributed databases (SDD-1)
Authors: Bernstein Philip A. , Shipman David W. , Rothnie James B.
Published: July 2002

This paper presents the concurrency control strategy of SDD-1. SDD-1, a System for Distributed Databases, is a prototype distributed database system being developed by Computer Corporation of America. In SDD-1, portions of data distributed throughout a network may be replicated at multiple sites. The SDD-1 concurrency control guarantees database consistency in the face of such distribution and replication.

This paper is one of a series of companion papers on SDD-1 [4, 10, 12, 21].
An authorization mechanism for a relational database system
Authors: Griffiths Patricia P. , Wade Bradford W.
Published: July 2002

A multiuser database system must selectively permit users to share data, while retaining the ability to restrict data access. There must be a mechanism to provide protection and security, permitting information to be accessed only by properly authorized users. Further, when tables or restricted views of tables are created and destroyed dynamically, the granting, authentication, and revocation of authorization to use them must also be dynamic. Each of these issues and their solutions in the context of the relational database management system System R are discussed.

When a database user creates a table, he is fully and solely authorized to perform upon it actions such as read, insert, update, and delete. He may explicitly grant to any other user any or all of his privileges on the table. In addition he may specify that that user is authorized to further grant these privileges to still other users. The result is a directed graph of granted privileges originating from the table creator.

At some later time a user A may revoke some or all of the privileges which he previously granted to another user B. This action usually revokes the entire subgraph of the grants originating from A's grant to B. It may be, however, that B will still possess the revoked privileges by means of a grant from another user C, and therefore some or all of B's grants should not be revoked. This problem is discussed in detail, and an algorithm for detecting exactly which of B's grants should be revoked is presented.
Precision Weighting—An Effective Automatic Indexing Method
Authors: Yu C. T. , Salton G.
Published: July 2002

A great many automatic indexing methods have been implemented and evaluated over the last few years, and automatic procedures comparable in effectiveness to conventional manual ones are now easy to generate. Two drawbacks of the available automatic indexing methods are the absence of reliable linguistic inputs during the indexing process and the lack of formal, analytical proofs concerning the effectiveness of the proposed methods.

The precision weighting procedure described in the present study uses relevance criteria to weight the terms occurring in user queries as a function of the balance between relevant and nonrelevant documents in which these terms occur; this approximates a semantic know-how of term importance. Formal mathematical proofs are given under well-defined conditions of the effectiveness of the method.
Generation of large-scale quadratic programs for use as global optimization test problems
Authors: Pardalos Panos M.
Published: July 2002

A method is presented for the generation of test problems for global optimization algorithms. Given
a bounded polyhedron in R and a vertex, the method constructs nonconvex quadratic functions
(concave or indefinite) whose global minimum is attained at the selected vertex. The construction
requires only the use of linear programming and linear systems of equations.
Human-Computer Interaction in the Control of Dynamic Systems
Authors: Rouse William B.
Published: July 2002

Modes of human-computer interaction in the control of dynamic
systems are discussed, and the problem of allocating tasks between
human and computer considered. Models of human performance in a
variety of tasks associated with the control of dynamic systems are
reviewed. These models are evaluated in the context of a design
example involving human-computer interaction in aircraft
operations. Other examples include power plants, chemical plants,
and ships.