Showing papers on "Operator (computer programming) published in 1994"

An exact separation of the spin‐free and spin‐dependent terms of the Dirac–Coulomb–Breit Hamiltonian

Abstract: The Dirac Hamiltonian is transformed by extracting the operator (sigma x p)/2mc from the small component of the wave function and applying it to the operators of the original Hamiltonian. The resultant operators contain products of Paull matrices that can be rearranged to give spin-free and spin-dependent operators. These operators are the ones encountered in the Breit-Pauli Hamiltonian, as well as some of higher order in alpha(sup 2). However, since the transformation of the original Dirac Hamiltonian is exact, the new Hamiltonian can be used in variational calculations, with or without the spin-dependent terms. The new small component functions have the same symmetry properties as the large component. Use of only the spin-free terms of the new Hamiltonian permits the same factorization over spin variables as in nonrelativistic theory, and therefore all the post-Self-Consistent Field (SCF) machinery of nonrelativistic calculations can be applied. However, the single-particle functions are two-component orbitals having a large and small component, and the SCF methods must be modified accordingly. Numerical examples are presented, and comparisons are made with the spin-free second-order Douglas-Kroll transformed Hamiltonian of Hess.

Volcano/spl minus/an extensible and parallel query evaluation system

Abstract: To investigate the interactions of extensibility and parallelism in database query processing, we have developed a new dataflow query execution system called Volcano. The Volcano effort provides a rich environment for research and education in database systems design, heuristics for query optimization, parallel query execution, and resource allocation. Volcano uses a standard interface between algebra operators, allowing easy addition of new operators and operator implementations. Operations on individual items, e.g., predicates, are imported into the query processing operators using support functions. The semantics of support functions is not prescribed; any data type including complex objects and any operation can be realized. Thus, Volcano is extensible with new operators, algorithms, data types, and type-specific methods. Volcano includes two novel meta-operators. The choose-plan meta-operator supports dynamic query evaluation plans that allow delaying selected optimization decisions until run-time, e.g., for embedded queries with free variables. The exchange meta-operator supports intra-operator parallelism on partitioned datasets and both vertical and horizontal inter-operator parallelism, translating between demand-driven dataflow within processes and data-driven dataflow between processes. All operators, with the exception of the exchange operator, have been designed and implemented in a single-process environment, and parallelized using the exchange operator. Even operators not yet designed can be parallelized using this new operator if they use and provide the interator interface. Thus, the issues of data manipulation and parallelism have become orthogonal, making Volcano the first implemented query execution engine that effectively combines extensibility and parallelism. >

Fourier finite-difference migration

Abstract: Many existing migration schemes cannot simultaneously handle the two most important problems of migration: imaging of steep dips and imaging in media with arbitrary velocity variations in all directions. For example, phase‐shift (ω, k) migration is accurate for nearly all dips but it is limited to very simple velocity functions. On the other hand, finite‐difference schemes based on one‐way wave equations consider arbitrary velocity functions but they attenuate steeply dipping events. We propose a new hybrid migration method, named “Fourier finite‐difference migration,” wherein the downward‐continuation operator is split into two downward‐continuation operators: one operator is a phase‐shift operator for a chosen constant background velocity, and the other operator is an optimized finite‐difference operator for the varying component of the velocity function. If there is no variation of velocity, then only a phase‐shift operator will be applied automatically. On the other hand, if there is a strong variatio...

Ill-Posed Problems: Theory and Applications

Abstract: Preface. Introduction. 1. General problems of regularizability. 2. Regularizing algorithms on compacta. 3. Tikhonov's scheme for constructing regularizing algorithms. 4. General technique for constructing linear RA for linear problems in Hilbert space. 5. Iterative algorithms for solving nonlinear ill-posed problems with monotonic operators. Principle of iterative regularization. 6. Applications of the principle of iterative regularization. 7. Iterative methods for solving nonlinear ill-posed operator equations with non-monotonic operators. 8. Application of regularizing algorithms to solving practical problems. Bibliography. Index.

Local Systems of Vertex Operators, Vertex Superalgebras and Modules

Abstract: We give an analogue for vertex operator algebras and superalgebras of the notion of endomorphism ring of a vector space by means of a notion of ``local system of vertex operators'' for a (super) vector space. We first prove that any local system of vertex operators on a (super) vector space $M$ has a natural vertex (super)algebra structure with $M$ as a module. Then we prove that for a vertex (operator) superalgebra $V$, giving a $V$-module $M$ is equivalent to giving a vertex (operator) superalgebra homomorphism from $V$ to some local system of vertex operators on $M$. As applications, we prove that certain lowest weight modules for some well-known infinite-dimensional Lie algebras or Lie superalgebras have natural vertex operator superalgebra structures. We prove the rationality of vertex operator superalgebras associated to standard modules for an affine algebra. We also give an analogue of the notion of the space of linear homomorphisms from one module to another for a Lie algebra by introducing a notion of ``generalized intertwining operators.'' We prove that $G(M^{1},M^{2})$, the space of generalized intertwining operators from one module $M^{1}$ to another module $M^{2}$ for a vertex operator superalgebra $V$, is a generalized $V$-module. Furthermore, we prove that for a fixed vertex operator superalgebra $V$ and

Regular linear systems with feedback

Abstract: We consider a rather general class of infinite-dimensional linear systems, called regular linear systems, for which convenient representations are known to exist both in time and in the frequency domain. We introduce and study the concept of admissible feedback operator for such a system and of well-posedness radius. We show that the closed-loop system obtained from a regular linear system with an admissible feedback operator is again regular and we describe the relationship between the generating operators of the open-loop and closed-loop systems.

The Algebra of Timed Processes, ATP

Abstract: The algebra of timed processes, ATP, uses a notion of discrete global time and suggests a conceptual framework for introducing time by extending untimed languages. The action vocabularly of ATP contains a special element representing the progress of time. The algebra has, apart from standard operators of process algebras such as prefixing by an action, alternative choice, and parallel composition, a primitive unit-delay operator. For two arguments, processes P and Q, this operator gives a process which behaves as P before the execution of a time event and behaves as Q afterwards. It is shown that several d-unit delay constructs such as timeouts and watchdogs can be expressed in terms of the unit-delay operator and standard process algebra operators. A sound and complete axiomatization for bisimulation semantics is studied and two examples illustrating the adequacy of the language for the description of timed systems are given. Finally we provide a comparison with existing timed process algebras.

Existence Families, Functional Calculi, and Evolution Equations

Abstract: Intuition and elementary examples.- Existence families.- Regularized semigroups.- The solution space of an operator and automatic well-posedness.- Exponentially bounded (Banach) solution spaces.- Well-posedness on a larger space Generalized solutions.- Entire vectors and entire existence families.- Reversibility of parabolic problems.- The cauchy problem for the Laplace equation.- Boundary values of holomorphic semigroups.- The Schrodinger equation.- Functional calculus for commuting generators of bounded strongly continuous groups.- Petrovsky correct matrices of generators of bounded strongly continuous groups.- Arbitrary matrices of generators of bounded strongly continuous groups.- More examples of regularized semigroups.- Existence and uniqueness families.- C-resolvents and Hille-Yosida type theorems.- Relationship to integrated semigroups.- Perturbations.- Type of an operator.- Holomorphic C-existence families.- Unbounded holomorphic functional calculus for operators with polynomially bounded resolvents.- Spectral conditions guaranteeing solutions of the abstract Cauchy problem.- Polynomials of generators.- Iterated abstract Cauchy problems.- Equipartition of energy.- Simultaneous solution space.- Exponentially bounded simultaneous solution space.- Simultaneous existence families.- Simultaneous existence families for matrices of operators.- Time dependent evolution equations.

The algebra of genetic algorithms

Abstract: A rigorous formulation of the generalisation of schema analysis known as forma analysis is presented. This is shown to provide a direct mechanism for harnessing knowledge about a search space, codified through the imposition of equivalence relations over that space, to generate a genetic representation and operators. It is shown that a single characterisation of a space leads to a unique genetic representation, and the kinds of representations that are possible are classified and discussed. A relatively new operator, calledrandom assorting recombination (RAR w ), is defined rigorously and is shown to be, in an important sense, a universal recombination operator.

Concurrent Objects in a Process Calculus

Abstract: A programming style based on concurrent objects arises almost inevitably in languages where processes communicate by exchanging data on channels. Using the pict language as an experimental testbed, we introduce a simple object-based programming style and compare three techniques for controlling concurrency between methods in this setting: explicit locking, a standard choice operator, and a more refined replicated choice operator.

Discrete Magnetic Laplacian

Abstract: We consider a 2-dimensional discrete operator which we call the Discrete Magnetic Laplacian (DML); it is an analogue of the magnetic Schrodinger operator. It follows from well known arguments that DML has the same spectrum (as a subset inR) as the Almost Mathieu operator (AM). They also have the same Integrated Density of States (IDS) which is known to be continuous. We show that DML is an element in a II1-factor and its IDS can be expressed through the trace in the II1-factor. It follows that DML never has anyL2-eigenfunctions (i.e. has no point spectrum). Then we formulate a natural algebraic conjecture which implies that the spectrum of DML (hence the spectrum of AM) is a Cantor set.

Virtual image display management system with head-up display

Abstract: A virtual image display management system using a head-up display that improves the ability of an operator of an automobile, or other equipment, to focus on primary functions, such as vehicle operation, while providing secondary information within the operator's primary visual field without requiring the operator to refocus. The present virtual image display management system integrates one or more secondary function displays into one reconfigurable virtual image head-up display. Several secondary functions are displayed sequentially using analog/digital symbology, icon representation, alphanumeric text or static/motion picture format. The operator may select secondary functions to be monitored, the display format, and the data acquisition intervals. A reconfigurable virtual image display processor accommodates more sophisticated sensor and communication functionality without penalizing efficiency and safety of the operator's primary functions. The present system integrates, interprets, selects and displays data derived from multiple sensors and communications systems at an optimum visual location within the operator's primary field of view. By displaying data in this fashion, an operator can vigilantly perform critical system functions while being kept well-informed of vehicle performance data, communication data and other useful functions and information.

Collective fields, Calogero-Sutherland model and generalized matrix models

Abstract: On the basis of the collective field method, we analyze the Calogero--Sutherland model (CSM) and the Selberg--Aomoto integral, which defines, in particular case, the partition function of the matrix models. Vertex operator realizations for some of the eigenstates (the Jack polynomials) of the CSM Hamiltonian are obtained. We derive Virasoro constraint for the generalized matrix models and indicate relations with the CSM operators. Similar results are presented for the $q$--deformed case (the Macdonald operator and polynomials), which gives the generating functional of infinitely many conserved charges in the CSM.

A Tensor Framework for Multidimensional Signal Processing

Abstract: This thesis deals with ltering of multidimensional signals. A large part of the thesis is devoted to a novel filtering method termed "Normalized convolution". The method performs local expansion of a signal in a chosen lter basis which not necessarily has to be orthonormal. A key feature of the method is that it can deal with uncertain data when additional certainty statements are available for the data and/or the lters. It is shown how false operator responses due to missing or uncertain data can be significantly reduced or eliminated using this technique. Perhaps the most well-known of such eects are the various 'edge effects' which invariably occur at the edges of the input data set. The method is an example of the signal/certainty - philosophy, i.e. the separation of both data and operator into a signal part and a certainty part. An estimate of the certainty must accompany the data. Missing data are simply handled by setting the certainty to zero. Localization or windowing of operators is done using an applicability function, the operator equivalent to certainty, not by changing the actual operator coefficients. Spatially or temporally limited operators are handled by setting the applicability function to zero outside the window. The use of tensors in estimation of local structure and orientation using spatiotemporal quadrature filters is reviewed and related to dual tensor bases. The tensor representation conveys the degree and type of local anisotropy. For image sequences, the shape of the tensors describe the local structure of the spatiotemporal neighbourhood and provides information about local velocity. The tensor representation also conveys information for deciding if true flow or only normal flow is present. It is shown how normal flow estimates can be combined into a true flow using averaging of this tensor eld description. Important aspects of representation and techniques for grouping local orientation estimates into global line information are discussed. The uniformity of some standard parameter spaces for line segmentation is investigated. The analysis shows that, to avoid discontinuities, great care should be taken when choosing the parameter space for a particular problem. A new parameter mapping well suited for line extraction, the Mobius strip parameterization, is de ned. The method has similarities to the Hough Transform. Estimation of local frequency and bandwidth is also discussed. Local frequency is an important concept which provides an indication of the appropriate range of scales for subsequent analysis. One-dimensional and two-dimensional examples of local frequency estimation are given. The local bandwidth estimate is used for dening a certainty measure. The certainty measure enables the use of a normalized averaging process increasing robustness and accuracy of the frequency statements.

Electromyographic virtual reality system

Abstract: A finite element model of a structure is manipulated according to electromyographic signal from the musculature of an operator The resulting forces are fed back to the operator and a display provides visual feedback of the resulting displacements

Renormalization of gauge invariant operators and anomalies in Yang-Mills theory

Abstract: A long-standing conjecture on the structure of renormalized, gauge invariant, integrated operators of arbitrary dimension in Yang-Mills theory is established. The general solution of the consistency condition for anomalies with sources included is also derived. This is achieved by computing explicitly the cohomology of the full unrestricted Becchi-Rouet-Stora-Tyutin operator in the space of local polynomial functionals with ghost number equal to zero or one. The argument does not use power counting and is purely cohomological. It relies crucially on standard properties of the antifeld formalism.

Conservative Shape-Preserving Two-Dimensional Transport on a Spherical Reduced Grid

Abstract: A new discretization of the transport equation for two-dimensional transport is introduced. The scheme is two time level, shape preserving, and solves the transport equation in flux form. It uses an upwind-biased stencil of points. To ameliorate the very restrictive constraint on the length of the time step appearing with a regular (equiangular) grid near the pole (generated by the Courant-Friedrichs-Lewy restriction), the scheme is generalized to work on a reduced grid. Application on the reduced grid allows a much longer time step to be used. The method is applied to the test of advection of a coherent structure by solid body rotation on the sphere over the poles. The scheme is shown to be as accurate as current semi-Lagrangian algorithms and is inherently conservative. Tests that use operator splitting in its simplest form (where the 2D transport operator is approximated by applying a sequence of 1D operators for a nondivergent flow field) reveal large errors compared to the proposed unsplit s...

Learning Planning Operators by Observation and Practice.

Abstract: The work described in this paper addresses learning planning operators by observing expert agents and subsequent knowledge refinement in a learning-by-doing paradigm. The observations of the expert agent consist of: 1) the sequence of actions being executed, 2) the state in which each action is executed, and 3) the state resulting from the execution of each action. Planning operators are learned from these observation sequences in an incremental fashion utilizing a conservative specific-to-general inductive generalization process. In order to refine the new operators to make them correct and complete, the system uses the new operators to solve practice problems, analyzing and learning from the execution traces of the resulting solutions or execution failures. We describe techniques for planning and plan repair with incorrect and incomplete domain knowledge, and for operator refinement through a process which integrates planning, execution, and plan repair. Our learning method is implemented on top of the PRODIGY architecture(Carbonell, Knoblock, & Minton 1990; Carbonell et al. 1992) and is demonstrated in the extended-strips domain(Minton 1988) and a subset the process planning domain(Gil 1991).

Pseudo-differential boundary value problems, conical singularities, and Asymptotics

Abstract: Mellin pseudo-differential operators discrete and continuous asymptotics the cone algebra boundary symbolic calculus Mellin operator conventions an analogue of Boutet de Monvel's algebra in the case of violated transmission property parametrics and elliptic regularity with asymptotics edge pseudo-differential operators edge Sobolev spaces.

Electronic automatic offer matching system for freezer exchange transactions among banks

Abstract: An electronic dealing system which performs foreign exchange transactions among banks etc. by matching terms of sale and terms of purchase, provided with a leave-order function whereby a dealing terminal may continue to place orders on the market and automatically perform transactions even after log-out processing. This enables transactions to be safely performed even when the operator is not present.

An operator interface for teleprogramming employing synthetic fixtures

Abstract: In the teleprogramming system an operator is presented with a virtual reality representation of a remote environment. The operator's interaction within that virtual environment is observed and translated into a sequence of robot program instructions for transmission to, and execution by, a robot at the remote site. In this paper we focus on operator interaction with the master station of the teleprogramming system. The use of synthetic fixtures to provide force and visual clues to assist the operator in performing tasks with speed and precision is discussed. It is suggested that, at least in some situations, it is both necessary and desirable to trade off realism for improved task performance. The difficulty of coping with exceptional conditions and, in particular, uncertainty in the world model used to generate the virtual environment is described and the operator interface for diagnosing and resolving errors is presented. An overview is also given of both the hardware and software used to implement the master station for the teleprogramming system.

Pseudospectra of the convection-diffusion operator

Abstract: The spectrum of the simplest 1D convection-diffusion operator is a discrete subset of the negative real axis, but the pseudospectra are regions in the complex plane that approximate parabolas. Put another way, the norm of the resolvent is exponentially large as a function of the Peclet number throughout a certain parabolic region. These observations have a simple physical basis and suggest that conventional spectral analysis for convection-diffusion operators may be of limited value in some applications.

Learning OWA operator weights from data

Abstract: We investigate the issue of obtaining the weights associated with the ordered weighted operator (OWA) aggregation in the situation when we have observed data on the arguments and the aggregated value. This provides a procedure to learn the decision maker's level of confidence from previous decisions. We next introduce a family of OWA operators called exponential OWA operators. >

Control unit for automobile audio system

Abstract: A control unit for an automobile audio system including a transmitting device mounted in correspondence with a shifter for permitting an operator to have easy access to the control unit so that control over the operation of the audio system may be obtained while the operator's hand is supported on the shifter.