bluuebunny/crossref_metadata_2025 huggingface dataset:
ASYMPTOTIC FORMULAS FOR DISCRETE EIGENVALUE PROBLEMS IN LIOUVILLE NORMAL FORM
Authors: de HOOG FRANK R. , ANDERSSEN ROBERT S.
Published: July 2002

In the analysis of both continuous and discrete eigenvalue problems, asymptotic formulas play a central and crucial role. For example, they have been fundamental in the derivation of results about the inversion of the free oscillation problem of the Earth and related inverse eigenvalue problems, the computation of uniformly valid eigenvalues approximations, the proof of results about the behavior of the eigenvalues of Sturm–Liouville problems with discontinuous coefficients, and the construction of a counterexample to the Backus–Gilbert conjecture. Useful formulas are available for continuous eigenvalue problems with general boundary conditions as well as for discrete eigenvalue problems with Dirichlet boundary condition. The purpose of this paper is the construction of asymptotic formulas for discrete eigenvalue problems with general boundary conditions. The motivation is the computation of uniformly valid eigenvalue approximations. It is now widely accepted that the algebraic correction procedure, first proposed by Paine et al.,13 is one of the simplest methods for computing uniformly valid approximations to a sequence of eigenvalues of a continuous eigenvalue problem in Liouville normal form.8 This relates to the fact that, for Liouville normal forms with Dirichlet boundary conditions, it is not too difficult to prove that such procedures yield, under quite weak regularity conditions, uniformly valid O(h2) approximations. For Liouville normal forms with general boundary conditions, the corresponding error analysis is technically more challenging. Now it is necessary to have, for such Liouville normal forms, higher order accurate asymptotic formulas for the eigenvalues and eigenfunctions of their continuous and discrete counterparts. Assuming that such asymptotic formulas are available, it has been shown1 how uniformly valid O(h2) results could be established for the application of the algebraic correction procedure to Liouville normal forms with general boundary conditions. Algorithmically, this methodology represents an efficient procedure for determining uniformly valid approximations to sequences of eigenvalues, even though it is more complex than for Liouville normal forms with Dirichlet boundary conditions. As well as giving a brief review of the subject for general (Robin) boundary conditions, this paper sketches proofs for the asymptotic formulas, for Robin boundary conditions, which are required in order to construct the mentioned O(h2) results.
FAST OSCILLATIONS IN A SINGULARLY PERTURBED PRODUCTION MODEL
Authors: STEINDL ALOIS
Published: July 2002

We investigate the behavior of a production model with non-convex operating cost and small adaption cost for the production rate. For zero adaption cost the optimal solution is known to be a chattering strategy, oscillating infinitely fast between two efficient production speeds. We show that for small values of the adaption cost a fast oscillation between the two states occurs.
A MODEL FOR THE COMPRESSIBLE FLOW THROUGH A POROUS MEDIUM
Authors: DE SOCIO L. M. , IANIRO N. , MARINO L.
Published: July 2002

A model for a continuum gas flowing through a porous matrix is proposed where the gas kinetics is governed by the Boltzmann equation and the solid phase by the energy equation. In the Boltzmann equation the integral relative to the gas–solid collisions is evaluated as for the collisions of hard spheres molecules against much heavier and longer straight particles (Lebowitz model of a sticks gas), randomly distributed in space according to a Maxwellian function with zero mean velocity. The mean flow is one-dimensional but the molecules are free to move in all three space dimensions. In the continuum limit, the moments of the Boltzmann equation provide the mass continuity, energy and momentum equations, the last one expressing the Darcy law for a compressible gas. The transport coefficients are analytically evaluated and a few examples are dealt with.
MULTIFLUID IONIZATION MODELS
Authors: BUET C. , CORDIER S. , RAVIART P. A.
Published: July 2002

In this paper, we present a multi-fluid ionization model. We prove that this stationary, mono-dimensional model has a maximal solution which is not global at variance with the mono-species case and we present a numerical method for solving this highly singular system of ordinary differential equations. Numerical results are compared with those obtained for other models.
LINEAR ELLIPTIC PROBLEMS WITH MIXED BOUNDARY CONDITIONS RELATED TO RADIATION HEAT TRANSFER
Authors: PORZIO MARIA MICHAELA , LÓPEZ-POUSO ÓSCAR
Published: July 2002

We prove the existence and uniqueness results for elliptic problems with L1 data and mixed boundary conditions which include as particular cases the Dirichlet and the Neumann problems.

These elliptic equations are related to radiation heat trasfer.
A NONLINEAR MATHEMATICAL MODEL FOR PULSATILE DISCHARGES OF LUTEINIZING HORMONE MEDIATED BY HYPOTHALAMIC AND EXTRA-HYPOTHALAMIC PATHWAYS
Authors: KUNPASURUANG WANNAPA , LENBURY YONGWIMON , HEK GEERTJE
Published: July 2002

A mathematical model of hormone secretion in the hypothalamo-pituitary-gonadal axis in man is extended to incorporate two different neural pathways, which have been suggested by clinical data to be capable of stimulating pulsatile discharges of LH (luteinizing hormone) independently of each other. Analysis of the nonlinear model is carried out through the use of geometric singular perturbation methods. In this way, existence of a limit cycle is proved for certain ranges of the system parameters. When the LH secretion rate independent of the hypothalamus is assumed constant, dropping the hypothalamus stimulated secretion term from the model blocks the hypothalamus pathway, implying that sustained oscillations in the hormone levels may not be attainable. Therefore, a sinusoidal term is incorporated into the model so that the system can still exhibit pulsatile LH secretion independent of the hypothalamus mediation. It is shown, by a construction of a bifurcation diagram, that the pulsatile hormone secretion can develop into chaotic dynamics when the amplitude of oscillation stimulated by extra-hypothalamic structures is high enough to disturb the synchrony of hypothalamic control. The resulting numerical simulation is found to compare well with the clinically observed data.
NONLINEAR STOCHASTIC WAVE EQUATION WITH COLOMBEAU GENERALIZED STOCHASTIC PROCESSES
Authors: NEDELJKOV MARKO , RAJTER DANIJELA
Published: July 2002

Colombeau generalized stochastic processes are introduced in order to solve nonlinear wave and Klein–Gordon equations with stochastic processes. Particular cases include one- and three-dimensional wave and Klein–Gordon equations with Lipschitz and cubic nonlinearities. In all cases, considered as Colombeau generalized stochastic processes, solutions are obtained and proved to be unique. The normalizations of the initial data and stochastic processes appear to be the crucial points for the existence of solutions to the above equations.
INTEGRAL EQUATION METHODS FOR MOLECULAR SCALE CALCULATIONS IN THE LIQUID PHASE
Authors: CANCÈS E. , BRIS C. LE , MENNUCCI B. , TOMASI J.
Published: July 2002

We report here a series of works1–5 devoted to the modelling of the liquid phase for quantum chemistry calculations. The question under consideration is the computation of the electrostatic interaction between charge densities in the presence of a continuum dielectric medium. It consists of solving an elliptic problem of the form - div (∊(x) ∇ V)=ρ where the field ∊(x) exhibits a discontinuity on a closed surface. We show how an enhanced use of integral equations methods has recently led to significant progress in this field: reduction of the computational cost in the standard cases, extension of existing methods to sophisticated cases out of reach so far, development of new possibilities. This work has a wide range of applications in chemistry and biology.
ON SENSITIVITY AND RELATED PHENOMENA IN THIN SHELLS WHICH ARE NOT GEOMETRICALLY RIGID
Authors: SANCHEZ-PALENCIA EVARISTE
Published: July 2002

We consider the asymptotic behavior as the thickness 2ε tends to zero of thin elastic shells which are not geometrically rigid for the kinematic boundary conditions (non-inhibited shells). It is known that the limit displacement belongs to the subspace G of inextensional displacements. We write the corresponding mixed formulation with a Lagrange multiplier. It is then proved that the corresponding problem (equations and boundary conditions) is not elliptic, whatever the type of the surface. Examples are given where the interior smoothness of the data does not imply interior smoothness of the solutions. The topology of the space M of the multipliers is weaker than the L2 topology. In some cases it is even weaker than that of distributions (sensitivity phenomenon). As a consequence, the convergence of the problem in mixed formulation for thickness 2ε as ε tends to zero only holds in very poor topologies, implying non-uniformity with respect to ε of the finite element mixed formulations.
PLANE LAMINAR FLAMES WITH MULTICOMPONENT TRANSPORT AND COMPLEX CHEMISTRY
Authors: GIOVANGIGLI VINCENT
Published: July 2002

We consider plane laminar flames with multicomponent transport and complex chemistry. The governing equations are derived from the kinetic theory of gases by using the classical isobaric approximation. An arbitrary number of reversible chemical reactions and temperature-dependent species specific heat is considered in the model. We also take into account the most general form for multicomponent transport fluxes given by the kinetic theory. Upon first considering a bounded domain and then letting the size of the domain to go to infinity, we obtain an existence theorem. We also establish that the natural entropy production norm associated with multicomponent diffusion is a solution-weighted norm.
BOUNDARY STABILIZATION FOR THE EXTENSIBLE BEAM WITH ATTACHED LOAD
Authors: DALSEN MARIÉ GROBBELAAR-VAN , VAN DER MERWE ALNA
Published: July 2002

When a load is attached to one end of an extensible beam whose ends are a fixed distance apart, the mathematical model describing the vibrations of the beam contains a nonlinearity in the partial differential equation as well as in the dynamical boundary condition. We show that uniform exponential stability can be achieved when closed loop feedback stabilization, consisting of two boundary controls, is incorporated at the point of contact between the load and the beam. Our analytical results are complemented by numerical results for the linear case.
WRINKLED ROD
Authors: JURAK M. , TUTEK Z.
Published: July 2002

The sequence of equilibrium displacements of periodically wrinkled elastic arches is considered. The middle curve of each arch is a plane periodic curve whose amplitude and period are assumed to be small. By the use of the two-scale convergence an approximate model for equilibrium displacement of wrinkled arch is derived. In this model, named wrinkled rod, elastic continuum is geometrically straight and the shape of the wrinkles enters into coefficients of the corresponding differential equations. It is proved that the sequence of equilibrium displacements of wrinkled arches approaches equilibrium displacement of wrinkled rod when both, period and amplitude, wrinkles tend to zero.
HIGH GAIN OUTPUT FEEDBACKS FOR SYSTEMS WITH DISTRIBUTED PARAMETERS
Authors: NIKITIN S. , NIKITINA M.
Published: July 2002

This paper deals with the high gain feedback stabilization of single input–single output (SISO) minimum-phase systems with distributed parameters. Sufficient conditions for an infinite-dimensional SISO system to be stabilized by a high gain output feedback are obtained. The results of this paper are useful for designing and tuning high gain output feedbacks in numerous industrial control applications.
APPROXIMATION OF BLOWING UP SOLUTIONS TO SEMILINEAR PARABOLIC EQUATIONS USING "MASS CONTROLLED" PARABOLIC SYSTEMS
Authors: FAYYAD D. , NASSIF N.
Published: July 2002

This paper considers asymptotic approximations to the solutions of the semilinear parabolic equation: [Formula: see text] where the function f(u) is such that the solution to (0.1) blows up in a finite time Tb. In order to control the explosive behavior of this problem, we consider a "perturbation" to (0.1) defined by: [Formula: see text] where ε is a small positive number. The boundary and initial conditions on uε are those of u. For vε, the initial and boundary conditions are chosen to be 1. Note that system (0.2) belongs to a class of coupled semilinear parabolic equations, with positive solutions and "mass control" property, (see Ref. 10). The solution {uε, vε} of such systems is known to be global. As such, (0.2) appears to be a regular perturbation to a singular problem (0.1). In this work, our basic theorem is a convergence proof for uε and [Formula: see text] to u and ut, respectively, in the L∞ norm. These results constitute a framework for designing in subsequent work, numerical algorithms for the computation of blow-up times (see Ref. 6).
LARGE NEURAL NETWORK: OBJECT MODELING AND PARALLEL SIMULATION
Authors: GARCÍA-ORELLANA C. J. , LÓPEZ-ALIGUÉ F. J. , GONZÁLEZ-VELASCO H. M. , MACÍAS-MACÍAS M. , ACEVEDO-SOTOCA M. I.
Published: July 2002

We propose an object oriented model for the simulation of large neural networks using the OMT technique. This modeling has been implemented on a client-server parallel simulator (called NeuSim-NNLIB), the server being a "beowulf" cluster, getting up to 18 MCPS with a cluster of 6 Pentium processors. We also present an estimation for simulator performance and optimal processors number.
DYNAMICS OF A GENERALIZED COSMOLOGICAL SCALAR–TENSOR THEORY
Authors: FUKUI TAKAO , OVERDUIN JAMES M.
Published: July 2002

A generalized scalar–tensor (GST) theory is investigated whose cosmological (or quintessence) term depends on both a scalar field and its time derivative. A correspondence with solutions of five-dimensional Space–Time–Matter (STM) theory is noted. Analytic solutions are found for the scale factor, scalar field and cosmological term. Models with free parameters of order unity are consistent with recent observational data and could be relevant to both the dark matter and cosmological "constant" problems.
PYRAMIDAL NEURONES IN MACAQUE VISUAL CORTEX: INTERAREAL PHENOTYPIC VARIATION OF DENDRITIC BRANCHING PATTERNS
Authors: JELINEK HERBERT F. , ELSTON GUY N.
Published: July 2002

The basal dendritic arbors of over 500-layer III pyramidal neurones of the macaque cortex were compared by fractal analyses, which provides a measure of the space filling (or branching pattern) of dendritic arbors. Fractal values (D) of individual cells were compared between the cytochrome oxidase (CO)-rich blobs and CO-poor interblobs of middle and upper layer III, and between sublaminae, in the primary visual area (V1). These data were compared with those in the CO compartments in the second visual area (V2), and seven other extrastriate cortical areas (V4, MT, LIP, 7a, TEO, TE and STP). There were significant differences in the fractal dimensions, and therefore the dendritic branching patterns, of cells in striate and extrastriate areas. Of the 55 possible pairwise comparisons of fractal dimension of neurones in different cortical areas (or CO compartments), 39 proved to be significantly different. The markedly different morphologies of pyramidal cells in the different cortical areas may be one of the features that determine the functional signatures of these cells by influencing the number of inputs received by, and propagation of potentials through, their dendritic arbors.
DEFINING QUALITY CLASSIFICATION CATEGORIES FOR COMPLEX SYSTEM PRODUCTS
Authors: HAMERI A.-P.
Published: July 2002

The paper describes the motivations, process and results of an activity defining the quality classification categories for a complicated system product. The underlying case project shares an objective to construct one of the largest scientific instrumentation ever built by mankind. This 10-year effort with significant technological, scientific, political and financial risks has reached manufacturing and partially the installation phase. It was realized that the key criteria to define the quality classification category for each equipment, item, part, subassembly and system must be done in relation to external world. A failure of an item or part must be assessed in respect of its anticipated hazard on environment, on expected performance of the system and on financial stability of the project. During the work, it was realized that each part should be evaluated separately, meaning that inheritance of quality categories cannot take place in the system. Once defined, quality categories dictate the level of detail used in engineering change, documentation and operational procedures of each part of the system. A more in-depth look on contact impact analysis between components of a complex system product is also provided. It is concluded that the approach provided in the paper can be applied to any system or artifact requiring design, production and assembly.
BEHIND THE QUANTUM CONFINEMENT AND SURFACE PASSIVATION OF NANOCLUSTERS
Authors: SUN CHANG Q. , GONG H. Q. , HING P. , YE H. T.
Published: July 2002

A new model is presented to describe the quantum confinement and surface passivation effects of nanoclusters. The quantum well depth (ϕ) and the band gap width (Eg) of nanoclusters are independent concepts, because the ϕ depends on the surface electron density while the Eg is a function of the crystal field of the solid. The ϕ and Eg can be correlated with the joint physical and chemical effects, which are quite simple but have rarely been noticed. It is suggested that the bond contraction at the surface and the rise in the surface-to-volume ratio (γ), as well as the cluster interaction, enhance intrinsically the crystal field and hence the band gap Eg. Reaction with electronegative elements, such as oxygen and nitrogen, widens extrinsically the Eg by producing holes below the Fermi level [Appl. Phys. Lett.72, 1706 (1998)]. The formulation agrees well with experimental observations on the band gap enlargement by reducing particle size.
REACTION OF WATER WITH CLEAN SURFACES OF MnO(100)
Authors: KENDELEWICZ T. , DOYLE C. S. , CARRIER X. , BROWN G. E.
Published: July 2002

Water adsorption on the MnO(100) single crystal surface was quantitatively monitored using chemical shifts in the O 1s core level spectra. We find that the initial reactions at low water vapor pressures of 10-8–10-4 Torr are limited to a small fraction of a monolayer and involve dissociation of water at or near defect centers resulting in surface hydroxyls. Even at these low pressures, there is an increase in water adsorption with increasing dosing time. Water uptake increases dramatically for vapor pressures between 10-4 and 10-2 Torr and then stabilizes above 10-2 Torr. At this pressure, hydroxyl coverages slightly exceed a monolayer. Hydroxyl species formed on this surface are unstable and can be removed by annealing to 200°C. These data are compared with those from similar studies of the interaction of water vapor with MgO(100) and the surfaces of iron oxides (α- Fe 2 O 3 and Fe 3 O 4), and some quantitative similarities and differences are discussed. In particular, the role of cooperative interactions in the condensed water overlayer in surface hydroxylation is emphasized.
AN UNUSUAL CASE OF HYPERPHALANGISM ASSOCIATED WITH FOREARM AND ELBOW ANOMALIES
Authors: Seradge H. , Wood V. E.
Published: July 2002

Hyperphalangism is characterized by an extra phalanx between the phalanges of a finger, usually excluding the thumb. This abnormality is distinguished from polydactyly and polyphalangism in that the hand has more phalanges in the fingers and no extra fingers. Because the digits are small and short, a better term to describe this abnormality would be "brachyhyperphalangism",7 but the term is cumbersome and unpopular.

We have reviewed the world literature up to the present time and have never seen reported elbow abnormalities associated with hyperphalangism.
RESISTANCE NOISE NEAR TO ELECTRICAL BREAKDOWN: STEADY STATE OF RANDOM NETWORKS AS A FUNCTION OF THE BIAS
Authors: PENNETTA C.
Published: July 2002

A short review is presented of a recently developed computational approach which allows the study of the resistance noise over the full range of bias values, from the linear regime up to electrical breakdown. Resistance noise is described in terms of two competing processes in a random resistor network. The two processes are thermally activated and driven by an electrical bias. In the linear regime, a scaling relation has been found between the relative variance of resistance fluctuations and the average resistance. The value of the critical exponent is significantly higher than that associated with 1/f noise. In the nonlinear regime, occurring when the bias overcomes the threshold value, the relative variance of resistance fluctuations scales with the bias. Two regions can be identified in this regime: a moderate bias region and a pre-breakdown one. In the first region, the scaling exponent has been found independent of the values of the model parameters and of the bias conditions. A strong nonlinearity emerges in the pre-breakdown region which is also characterized by non-Gaussian noise. The results compare well with measurements of electrical breakdown in composites and with electromigration experiments in metallic lines.
Biological self-organisation and pattern formation by way of microtubule reaction-diffusion processes
Authors: Tabony James , Vuillard Laurent , Papaseit Cyril
Published: July 2002

Chemically dissipative or Turing processes, have been predicted by theoreticians as a way by which an initially homogenous solution of chemicals or biochemicals can spontaneously self-organise and give rise to a macroscopic pattern by way of a combination of reaction and diffusion. They have been advanced as a possible underlying process for biological self-organisation and pattern formation. Until now, there have been no examples of in vitro biological substances showing this type of behaviour. Evidence is presented that microtubule solutions in vitro self-organise in this manner and that similar processes may occur in vivo during embryogenesis.
An accurate computation of the hypergeometric distribution function
Authors: Wu Trong
Published: July 2002

The computation of the cumulative hypergeometric distribution function is of interest to many researchers who are working in the computational sciences and related areas. Presented here is a new method for computing this function that applies prime number factorization to the factorials. We also apply cancellation to the numerator and denominator to reduce the computational complexity of the initial, the tail end, or weighted probabilities to achieve maximum accuracy. The new method includes two algorithms, one using recursion and the other using iteration. These two algorithms are machine independent; precision is arbitrary, subject to storage limitation. The development of the algorithms is discussed, and some test results and the comparison of these two algorithms are given. To implement both algorithms, we use the Ada programming language that is an American National Standard Institute standardized language. The language has special features such as
exception handling
and
tasks
.
Exception handling
is used to make programming easier and to prevent overflow or underflow conditions during the execution of the program.
Tasks
are used to compute the numerator and denominator concurrently, and to maximize the possible number of integer multiplications in the numerator and denominator. All of the computations can be done on currently available machines, and the time consumed by these computations remains reasonably small.
Topological considerations in isosurface generation
Authors: van Gelder Allen , Wilhelms Jane
Published: July 2002

A popular technique for rendition of isosurfaces in sampled data is to consider cells with sample points as corners and approximate the isosurface in each cell by one or more polygons whose vertices are obtained by interpolation of the sample data. That is, each polygon vertex is a point on a cell edge, between two adjacent sample points, where the function is estimated to equal the desired threshold value. The two sample points have values on opposite sides of the threshold, and the interpolated point is called an
intersection point
.

When one cell face has an intersection point in each of its four edges, then the correct connection among intersection points becomes ambiguous. An incorrect connection can lead to erroneous topology in the rendered surface, and possible discontinuities. We show that disambiguation methods, to be at all accurate, need to consider sample values in the neighborhood outside the cell. This paper studies the problems of disambiguation, reports on some solutions, and presents some statistics on the occurrence of such ambiguities.

A natural way to incorporate neighborhood information is through the use of calculated gradients at cell corners. They provide insight into the behavior of a function in well-understood ways. We introduce two
gradient consistency heuristics
that use calculated gradients at the corners of ambiguous faces, as well as the function values at those corners, to disambiguate at a reasonable computational cost. These methods give the correct topology on several examples that caused problems for other methods we examined.
Coupling the user interfaces of a multiuser program
Authors: Dewan Prasun , Choudhary Rajiv
Published: July 2002

We have developed a new model for coupling the user interfaces of a multiuser program. It is based on an interaction model and a user interface framework that allow users and programmers, respectively, to view applications as editors of data. It consists of a semantics model, a specification model, and an implementation model for coupling. The semantics model determines (1) which properties of interaction entities created for a user are shared with corresponding interaction entities created for other users and (2) when changes made by a user to a property of an interaction entity are communicated to other users sharing it. It divides the properties of an interaction entity into multiple coupling sets and allows users to share different coupling sets independently. It supports several criteria for choosing when a change made by a user to a shared property is communicated to other users. These criteria include how structurally complete the change is, how correct it is, and the time at which it was made. The specification model determines how users specify the desired semantics of coupling. It associates interaction entities with inheritable coupling attributes, allows multiple users to specify values of these attributes, and does a runtime matching of the coupling attributes specified by different users to derive the coupling among their user interfaces. The implementation model determines how multiuser programs implement user-customizable coupling. It divides the task of implementing the coupling between system-provided modules and application programs. The modules support automatically a predefined semantics and specification model that can be extended by the programs. We have implemented the coupling model as part of a system called Suite. This paper describes and motivates the model using the concrete example of Suite, discusses how aspects of it can be implemented in other systems, compares it with related work, discusses its shortcomings, and suggests directions for future work.
Secure communication using remote procedure calls
Authors: Birrell Andrew D.
Published: July 2002

Research on encryption-based secure communication protocols has reached a stage where it is feasible to construct end-to-end secure protocols. The design of such a protocol, built as part of a remote procedure call package, is described. The security abstraction presented to users of the package, the authentication mechanisms, and the protocol for encrypting and verifying remote calls are also described.
Model and representation
Authors: Douglas Sarah A. , Kirkpatrick Arthur E.
Published: July 2002

User interfaces for color selection consist of a visible screen
representation, an input method, and the underlying conceptual organization of the color model. We report a two-way factorial, between-subjects variable experiment that tested the effect of high and low visual feedback interfaces on speed and accuracy of color matching for RGB and HSV color models. The only significant effect was improved accuracy due to increased visual feedback. Using color groups as a within-subjects variable, we found differences in performance of both speed and accuracy. We recommend that experimental tests adopt a color test set that does not show bias toward a particular model, but is based instead on a range of colors that would be most likely matched in practice by people using color selection software. We recomment the Macbeth Color Checker naturals, primaries, and grays. As a follow-up study, a qualitative case analysis of the way users navigated through the color space indicates that feedback helps users with limited knowledge of the model, allowing them to refine their match to a higher degree of accuracy. Users with very little or a lot of knowledge of the color model do not appear to be aided by increased feedback. In conclusion, we suggest that visual feedback and design of the interface may be a more important factor in improving the usability of a color selection interface than the particular color model used.
An extension of the performance of a database manager in a virtual memory system using partially locked virtual buffers
Authors: Brice Richard S. , Sherman Stephen W.
Published: July 2002

Buffer pools are created and managed in database systems in order to reduce the total number of accesses to the I/O devices. In systems using virtual memory, any reduction in I/O accesses may be accompanied by an increase in paging. The effects of these factors on system performance are quantified, where system performance is a function of page faults and database accesses to the I/O devices. A previous study of this phenomenon is extended through the analysis of empirical data gathered in a multifactor experiment. In this study memory is partitioned between the program and the buffer so that the impact of the controlled factors can be more effectively evaluated. It is possible to improve system performance through the use of different paging algorithms in the program partition and the buffer partition. Also, the effects on system performance as the virtual buffer size is increased beyond the real memory allocated to the buffer partition are investigated.
The Association for Computing Machinery
Authors: Williams Samuel B.
Published: July 2002

As the Association for Computing Machinery enters a new phase of its existence, it seems befitting to review, briefly, the conditions in the computing field just prior to its organization and the events of the past six years of its life. Since its formation, in 1947, the Association has adhered to the originally established policy of informality. That is, meetings and discussions were encouraged and information was generally put out in mimeographed form and more formal publications were discouraged. The function of the organization was to maintain a mailing list of members paying only such dues as were necessary to cover the cost of printing or mimeographing and mailing. Such an organization served its purpose excellently, but times have changed.

Prior to the formation of the Association, the automatic computing field, as such, hardly existed. Probably the first meeting of those interested in the field was held at the Massachusetts Institute of Technology in 1945. The occasion was to introduce the differential analyzer, designed by Dr. Vannevar Bush and Dr. Samuel H. Caldwell, to the public. This machine is a refinement of the original machine built by Dr. Bush in 1925. The earlier machine served as a pattern for several machines which were in operation in 1945, including those at the Aberdeen Proving Ground, the Moore School of Electrical Engineering, the General Electric Company and in Manchester, England.

It is interesting to note that, at the time of this first meeting, other analog type machines were in operation. Network analyzers were employed to simulate power distribution systems and aid in their study. None of these machines employed digital representation but represented the values in analog form, such as voltage, current or angular position. Digital computation was possible only by hand operated calculators or by some business machines.

Although automatic digital computation by machinery was the goal Charles Babbage strove to reach, it was not until the Hollerith rotary counter was suggested in 1890 and the International Business Machines Corporation began producing machines employing such counters for accounting purposes in the period from 1903 to 1905, that such goal was reached. The automatic multiplying punch machine was not produced until 1931.

Computation by means of telephone relays was first introduced in the Bell System Complex Computer, known as Model I, in 1939. The method of employing the relays was suggested by Dr. George R. Stibitz and the machine was designed by Samuel B. Williams. This was not a fully automatic machine. The complex quantities for a single
A Survey of Microcellular Research
Authors: Minnick Robert C.
Published: July 2002

This paper is a survey of research on microcellular techniques. Of particular interest are those techniques that are appropriate for realization by modern batch-fabrication processes, since the rapid emergence of reliable and economical batch-fabricated components represents probably the most important current trend in the field of digital circuits.

First the manufacturing methods for batch-fabricated components are reviewed, and the advantages to be realized from the application of the principles of cellular logic design are discussed. Also two categorizations of cellular arrays are made in terms of the complexity of each cell (only low-complexity cells are considered) and in terms of the various application areas.

After a survey of very early techniques that can be viewed as exemplifying cellular approaches, modern-day cellular arrays are discussed on the basis of whether they are fixed cell-function arrays or variable cell-function arrays. In the fixed cell-function arrays the switching function produced by each cell is fixed; the cell parameters are used only in the modification of the interconnection structure. Several versions of NOR gate arrays, majority gate arrays, adder arrays, and others are reviewed in terms of synthesis techniques and array growth rates.

Similarly, the current status of research is summarized in variable cell-function arrays, where not only the interconnection structure but also the function produced by each cell is determined by parameter selection. These arrays include various general function cascades, outpoint arrays, and cobweb arrays, for example. Again, the various cell types that have been considered are pointed out, as well as synthesis procedures and growth rates appropriate for them.

Finally, several areas requiring further research effort are summarized. These include the need for more realistic measures of array growth rates, the need for synthesis techniques for multiple-function arrays and programmable arrays, and the need for fault-avoidance algorithms in integrated structures.
Numerical Solution of Parabolic Partial Differential Equations With Two-Point Boundary Conditions by Use of the Method of Lines
Authors: Hicks J. S. , Wei J.
Published: July 2002

The Method of Lines, a numerical technique commonly used for solving partial differential equations on analog computers, is used to attain digital computer solutions of such equations. An extensive theoretical development is presented that establishes convergence and stability for one-dimensional parabolic equations with Dirichlet boundary conditions. A new modification of the method, using noncentral differences, is shown to be much faster, in terms of computer time, than conventional grid methods, for two examples.
Arcs and Curves in Digital Pictures
Authors: Rosenfeld Azriel
Published: July 2002

Characterizations of digital “simple arcs” and “simple closed curves” are given. In particular, it is shown that the following are equivalent for sets
S
having more than four points: (1)
S
is a simple curve; (2)
S
is connected and each point of
S
has exactly two neighbors in
S
; (3)
S
is connected, has exactly one hole, and has no deletable points. It follows that if a “shrinking” algorithm is applied to a connected
S
that has exactly one hole, it shrinks to a simple curve.
An Algorithm for Structuring Flowgraphs
Authors: Baker Brenda S.
Published: July 2002

This paper describes an algorithm which transforms a flowgraph into a program containing control constructs such as if then else statements, repeat (do forever) statements, multilevel break statements (causing jumps out of enclosing repeats), and multilevel next statements (causing jumps to iterations of enclosing repeats). The algorithm can be extended to create other types of control constructs, such as while or until. The program appears natural because the constructs are used according to common programming practices. The algorithm does not copy code, create subroutines, or add new variables. Instead, goto statements are generated when no other available control construct describes the flow of control. The algorithm has been implemented in a program called STRUCT which rewrites Fortran programs using constructs such as while, repeat, and if then else statements. The resulting programs are substantially more readable than their Fortran counterparts.
Accelerating the convergence of random search methods for discrete stochastic optimization
Authors: Andradóttir Sigrún
Published: July 2002

We discuss the choice of the estimation of the optimal solution when random search methods are applied to solve discrete stochastic optimization problems. At the present time, such optimization methods usually estimate the optimal solution using either the feasible solution the method is currently exploring or the feasible solution visited most often so far by the method. We propose using all the observed objective function values generated as the random search method moves around the feasible region seeking an optimal solution to obtain increasingly more precise estimates of the objective function values at the different points in the feasible region. At any given time, the feasible solution that has the best estimated objective function value (largest one for maximization problems; the smallest one for minimization problems) is used as the estimate of the optimal solution. We discuss the advantages of using this approach for estimating the optimal solution and present numerical results showing that modifying an existing random search method to use tnhis approach for estimating the optimal soluation appears to yield improved performance. We also present sereval rate of convergence results for random search methods using our approach for estimating the optimal solution. One these random search methods is a new variant of the stochastic comparison method; in addition to specifying the rate of convergence of this method, we prove that it is guaranteed to converge almost surely to the set of global optimal solutions and present a result that demonstrates that this method is likely to perform well in practice.
Accurate approximate solution of partial differential equations at off-mesh points
Authors: Enright W. H.
Published: July 2002

Numerical methods for partial differential equations often determine approximations that are more accurate at the set of discrete meshpoints than they are at the “off-mesh” points in the domain of interest. These methods are generally most effective if they are allowed to adjust the location of the mesh points to match the local behavior of the solution. Different methods will typically generate their respective approximations on incompatible, unstructured meshes, and it can be difficult to evaluate the quality of a particular solution, or to visualize important properties of a solution. In this paper we will introduce a generic approach which can be used to generate approximate solution values at arbitrary points in the domain of interest for any method that determines approximations to the solution and low-order derivatives at meshpoints. This approach is based on associating a set of “collocation” points with each mesh element and requiring that the local approximation interpolate the meshpoint data and almost satisfy the partial differential equation at the collocation points. The accuracy associated with this interpolation/collocation approach is consistent with the “meshpoint accuracy” of the underlying method. The approach that we develop applies to a large class of methods and problems. It uses local information only and is therefore particularly suitable for implementation in a parallel or network computing environment. Numerical examples are given for some second-order problems in two and three dimensions.
A formalism for translator interactions
Authors: Earley Jay , Sturgis Howard
Published: July 2002

A formalism is presented for describing the actions of processors for programming languages—compilers, interpreters, assemblers—and their interactions in complex systems such as compiler-compilers or extendible languages. The formalism here might be used to define and answer such a question as “Can one do bootstrapping using a metacompiler whose metaphase is interpretive?” In addition an algorithm is presented for deciding whether or not a given system can be produced from a given set of component processors.
Garbage collection for virtual memory computer systems
Authors: Baecker H. D.
Published: July 2002

In list processing there is typically a growing demand for space during program execution. This paper examines the practical implications of this growth within a virtual memory computer system, proposes two new garbage collection techniques for virtual memory systems, and compares them with traditional methods by discussion and by simulation.
A parser-generating system for constructing compressed compilers
Authors: Mickunas M. D. , Schneider V. B.
Published: July 2002

This paper describes a parser-generating system (PGS) currently in use on the CDC-6500 computer at Purdue University. The PGS is a Fortran-coded program that accepts a translation grammar as input and constructs from it a compact, machine-coded compiler. In the input translation grammar, each BNF syntactic rule corresponds to a (possibly empty) “code generator” realizable as an assembly language, Fortran or Algol, subroutine that is called whenever that syntactic rule is applied in the parse of a program.

Typical one-pass compilers constructed by the PGS translate source programs at speeds approaching 14,000 cards per minute. For an XPL compiler, the parser program and its tables currently occupy 288 words of 60-bit core memory of which 140 words are parsing table entries and 82 words are links to code generators.
Two languages for estimating program efficiency
Authors: Cohen Jacques , Zuckerman Carl
Published: July 2002

Two languages enabling their users to estimate the efficiency of computer programs are presented. The program whose efficiency one wishes to estimate is written in the first language, a go-to-less programming language which includes most of the features of Algol 60. The second language consists of interactive commands enabling its users to provide additional information about the program written in the first language and to output results estimating its efficiency. Processors for the two languages are also described. The first processor is a syntax-directed translator which compiles a program into a symbolic formula representing the execution time for that program. The second processor is a set of procedures for algebraic manipulation which can be called by the user to operate on the formula produced by the first processor. Examples of the usage of the two languages are included. The limitations of the present system, its relation to Knuth's work on the analysis of algorithms, and some of the directions for further research are also discussed.
Structured data structures
Authors: Shneiderman Ben , Scheuermann Peter
Published: July 2002

Programming systems which permit arbitrary linked list structures enable the user to create complicated structures without sufficient protection. Deletions can result in unreachable data elements, and there is no guarantee that additions will be performed properly. To remedy this situation, this paper proposes a Data Structure Description and Manipulation Language which provides for the creation of a restricted class of data structures but ensures the correctness of the program. This is accomplished by an explicit structure declaration facility, a restriction on the permissible operations, and execution-time checks.
High-level binding with low-level linkers
Authors: Hamlet Richard G.
Published: July 2002

An easy to implement scheme is described by which a compiler can enforce agreement between complex data types in separately compiled modules. The scheme is designed to work with any existing link editor or linking loader, no matter how deficient. Obscure runtime errors caused by inconsistent usages are forestalled by static errors detected at linking time.
On the construction of a representative synthetic workload
Authors: Sreenivasan K. , Kleinman A. J.
Published: July 2002

A general method of constructing a drive workload representative of a real workload is described. The real workload is characterized by its demands on the various system resources. These characteristics of the real workload are obtained from the system accounting data. The characteristics of the drive workload are determined by matching the joint probability density of the real workload with that of the drive workload. The drive workload is realized by using a synthetic program in which the characteristics can be varied by varying the appropriate parameters. Calibration experiments are conducted to determine expressions relating the synthetic program parameters with the workload characteristics. The general method is applied to the case of two variables, cpu seconds and number of I/O activities; and a synthetic workload with 88 jobs is constructed to represent a month's workload consisting of about 6000 jobs.
Quadratic search for hash tables of sizes P
n
Authors: Ackerman A. Frank
Published: July 2002

It has previously been claimed [1 and 2] that the quadratic hash table search method of Maurer cannot usefully be applied to tables of size 2

n

. This is not so; the method can in fact be applied to tables of size

p
n

for any prime
p
. It is shown below that rather simple conditions on the coefficients suffice to guarantee that all table locations will be examined once and only once. Specifically, if the equation is
k
+
bi
2
+
ai
mod

p
n

(*) where
k
is the initial hash address and 0 ≤
i
<

p
n

, then, if
p
divides
b
but not
a
, the range of values is all the least positive residues of

p
n

. To prove that all values are covered, we consider some fixed value, say
k
+
bi
2
0
+
ai
0
mod

p
n

and ask, what conditions must be true if the congruence equation
k
+
bi
2
+
ai
≡
k
+
bi
0
2
+
ai
0
mod

p
n

is to have solutions
i
, 0 ≤
i
<

p
n

, other than
i
0
?