Showing papers on "Observer (quantum physics) published in 1984"

What happens when an accelerating observer detects a Rindler particle

Abstract: The nature of the interaction between a quantum field and an accelerating particle detector is analyzed from the point of view of an inertial observer. It is shown in detail for the simple case of a two-level detector how absorption of a Rindler particle corresponds to emission of a Minkowski particle. Several apparently paradoxical aspects of this process related to causality and energy conservation are discussed and resolved.

Acceleration radiation in interacting field theories

Abstract: Using the path-integral formulation of quantum field theory, we generalize the result that an accelerated observer sees a thermal spectrum to a large class of interacting field theories.

Reliability of Singing Bird Surveys: Changes in Observer Efficiency with Avian Density

Abstract: On tente d'estimer le biais methodologique lie a l'observateur lorsque la densite de population varie

Disturbance decoupled observer design via singular value decomposition

Abstract: Singular value decomposition is used to formulate a technique for the design of Luenberger observers when there are completely unknown system inputs.

The Everett Interpretation of Quantum Mechanics: Many Worlds or None?

Abstract: The doctoral dissertation of Hugh Everett, III-written under the direction of J. A. Wheeler-was principally motivated by the wish to obtain a reasonable basis for the quantization of general relativity (see Everett [1], pp. 454, 455, 462; and Wheeler [2], p. 465). To accomplish this aim, it seemed (and still does seem) necessary to eliminate from the formulation of the quantum theory the dualism of what von Neumann ([4], p. 351) called "process 1" and "process 2'" -the former associated with "observation of the object system from outside, the latter consisting in the evolution of an isolated quantum system; for general relativity deals essentially with the universe as a whole, and there is no such thing as "observation of the universe from outside." Thus Everett proposed to state the theory in such a way that all processes, including those of observation (or measurement), are of von Neumann's second type, governed uniformly by the quantum-dynamical law, the (timedependent) Schr6dinger equation. Now, it had been emphasized by von Neumann that, in distinguishing between "object system " and "apparatus-plus-observer" -and, correlatively, between " process 1" and "process 2" -there is considerable latitude as to where to draw the line: in the direction of including more in the "object system," according to von Neumann, one can go far into the body of the acual observer, and can include within "process 2" the neural and cerebral processes of sensation, as long as one does not trespass beyond the point where a result "is perceived by the observer" (see [4], pp. 351-2 and pp. 418-420). Indeed, it is not quite clear whether von Neumann intended even the last-mentioned restriction: he may have meant to allow the inclusion of arbitrary physiological occurrences within observers in process 2, and to have insisted only that at some point a line must be drawn and one must say "and suchand-such is perceived by the observer." In any case, it is already implicit in Schr6dinger's famous example ([5]) of the (possibly)

On the design of a decentralized observation scheme for large-scale systems

Abstract: The problem of designing a decentralized observation scheme with a specified convergence rate for a large-scale system that may be described as an interconnection of several subsystems is considered. A new mathematical result for the factorization of the interconnection matrix in a certain form is given and its application to the observer design problem is discussed. The present results demonstrate how a knowledge of the existing interconnection pattern can be exploited for improving the efficiency in such designs.

Modalized observers

Abstract: The purpose of this paper is to present a special full order observer which utilizes a priori information concerning the initial condition mismatch in its design. This a priori information and the use of an eigenstructure assignment procedure in the design leads to a reduction of the impact of the mismatch.

Compensation for Unbalance in Magnetic Bearing Systems

Abstract: An unbalance on a rotor causes vibration phenomena in the rotating machine. Thus balancing is an important process in manufacturing rotary machinery. Since perfect balancing is rather difficult there are often residual unbalances on the rotor. Moreover the rotor sometimes becomes unbalanced while the machine is in operation. To overcome these problems a new control method is presented for totally active magnetic bearing systems. By this method an unbalanced rotor can be suspended without unbalance vibrations by the magnetic bearing. The method is based on the theory of the output regulation with internal stability. The ways of designing the compensator are described as follows. (1) The system is stabilized by state feedbacks. (2) Since unbalance forces cannot be measured directly, an observer is constructed in order to estimate unbalance forces from measurable quantities: displacements and velocities of the rotor. (3) Using the outputs of the observer the unbalance forces are cancelled by controlling electromagnetic forces of the magnetic bearing. It is shown by numerical examples that the designed system can suspend an unbalanced rotor without whirling motions which appear when the compensation is not done. Moreover the effectiveness of the compensation for unbalance is experimentally studied by an instrument with Gyro mechanism.

Design and application of reduced-order adaptive observer with exponential rate of convergence for single-input single-output linear systems

Abstract: This paper is concerned with the design of an adaptive observer to estimate state variables and identify parameters of an unknown linear single-input single-output system with desired rate of exponential convergence. The observer structure is based on the Kreisselmeier types representation of parametrized form, but the adaptive law is obtained by a new scheme. The adaptive law is determined by equations forcing the errors into decreasing exponentially and it is designed to guarantee the asymptotic stability of the identification and estimation processes globally. A method of reducing the order of the adaptive law is also proposed. The reduction of the order is executed by using a priori information regarding relations between the unknown parameters. An experimental application using a heated tank with water jacket is included to show the practical effectiveness of the reduced-order adaptive scheme.

Estimation and control techniques for continuous culture fermentation processes.

Abstract: This article presents results obtained when some modern estimation and control techniques are applied to a simulated fermentation process. The control structure uses a particular observer of the substrate concentration and assumes the biomass concentration is measurable. The overall structure has been tested for both external and parametric disturbances, with very good results.

Minimal order observer design for linear time varying multivariable systems

Abstract: Based on a new canonical form for linear time varying systems we present a simple method for the design of minimal order observer. An especially desirable property of the observer is that the observer matrix is time invariant. Some examples are provided to illustrate the techniques.

Optimal object and edge localization in the presence of correlated noise

Abstract: The ideal observer for the task of object localization in the presence of correlated noise is implemented by means of the minimum chi-squared method, which is equivalent to the maximum likelihood method when the noise is additive and normally distributed. The prewhitening approach is explored in which the noise in the data is made uncorrelated by filtering the data with the filter S-1/2, where S is the noise power spectrum. The location of the object is then found by fitting a model of the object to the prewhitened data. A measure of the goodness of fit is proposed that is based upon the serial correlation in the prewhitened residuals, the difference between the data and the fit. These concepts are demonstrated by applying them to simulated data that possess known noise characteristics. It is shown that the accuracies predicted for the ideal observer can be achieved by the prewhitening technique.

Child's decorative garment

Abstract: A garment for human beings to cover at least the upper torso. On the garment is a decorative design having a specific cognitive orientation and is positioned such that the wearer readily recognizes the design. The design is further incorporated into an additional design having a specific cognitive orientation which is readily recognizable by a nonwearing observer.

Feedback Stabilization of Parabolic Distributed Parameter Systems by Discrete-Time Input–Output Data

Abstract: In this paper we investigate feedback stabilizability of continuous-time parabolic distributed parameter systems by discrete-time input-output data. We construct a stabilizer using the concepts of state feedback and output feedback through an observer. The design procedure is basically a modal approach which is realized in finite-dimensional theories and algorithms. It is shown that any initial state is reduced with an arbitrary decay rate. Explicit sufficient conditions are given for the convergence of the design scheme.

The observer SNR penalty for reconstructions from projections.

Abstract: Optimization of the efficiency of information collection in medical imaging requires simultaneous consideration of a number of factors, of which some are obvious, others subtle (1, 2). The factors taken singly seem to have little significance, whereas in concert they often lead to possibilities of more than an order of magnitude improvement in imaging efficiency, i.e., signal-to-noise ratio (SNR) squared per unit exposure or per unit exposure time. The purpose of this note is to point out one of the more subtle points related to CT and NMR information collection efficiency that must be considered when the concert is replayed using NM[R themes. We have found that a rigorous science of imaging can be built by studying the performance of the ideal observer of image data (3-6). The performance of real observers of conventional images seems to cluster about a point that falls short of ideal performance by a factor in the neighborhood of 2 when there is sufficient display contrast (7-9). Now, the ideal observer of images containing uncorrelated or white noise tests for the presence of a suspected lesion by a simple weighted average over the area of a lesion; the ideal observer of images containing negative correlations, such as the high-pass or ramp filter noise in CT, must take these correlations into account in testing for the lesion (10). This can be done either by using a rather complicated weighting in the average, or equivalently by first including a step to rewhiten the noise. Our experience with human observers is that they are incapable of this rewhitening step for a range of tasks of signal detection and signal discrimination that we have studied (9). In this work the signal parameters were explicitly specified for the observer a priori. We expect that human observers will continue to lack this capability for more complicated viewing tasks. This inability to cope with the negative correlatiions in image noise leads to what we call the “reconstruction/obsrver penalty” for images reconstructed from projections (“projection reconstruction” or PR images among MMR researchers). In conventional two-dimensional PR images this penalty is rigorously equal to ?r/2 for lesions with a Gaussian profile (3, 4) ; i.e., the exposure or imaging time required to obtain a given SNR is greater by a factor of 7r/2 for real observers of PR images than it would be for real observers of images from data not requiring the reconstruction process, all other factors being equal. In X-ray imaging this point is academic since the only way to avoid the PR process for an axial slice or tomogram is to excise the slice.

Robust observers and regulation for systems with parameters

Abstract: In many cases linear multivariable models describing physical systems contain structured uncertainties expressed in terms of parameters. In this paper we suggest conditions that guarantee the existence of a parameter free observer for the system. Conditions are also given under which this robust observer can be subsequently used in a parameter free controller configuration for regulation.

An objective formulation of orthodox quantum mechanics

Abstract: Relying on some concepts introduced in a companion paper, we set foth in this article a formulation of quantum theory that yields the same experimental predictions as those obtained from von Neumann's formulation. Moreover, this is accomplished in such a manner as to obviate the need for observer intervention.

Design of optimal observers for structural control

Abstract: An easy and fast approach based on the pole assignment method is given in order to design the optimal observer for high-order structural systems. It is shown that the optimal observer is not only the one which is characterised by an optimal gain; the optimal locations of the sensors and their types, the optimal locations of the control forces and their optimal design are also important factors in the design of the optimal observer used to control flexible structures. It has been found that the suitable sensor type and its location differ from one structure to another, depending on the natural frequencies and mode shapes of the structure. Two numerical examples are given to illustrate the application of this method.

Incomplete state feedback for time delay systems: Observer applications in multidelay compensation

Abstract: This paper demonstrates how a recently developed observer for time delay systems may be used to estimate needed state variables for implementation of multivariable time delay compensation. The general results are illustrated by an example of a multireactor plant in which only one reactor concentration can be measured. The observer worked well in simulation for both multivariable PID control and multidelay compensated PID control and allowed both schemes to function with estimated state variables in the feedback loop. 16 references, 5 figures.

Comments on "On the application of matrix generalized inverses to the design of observer for time-varying and time-invariant linear systems"

Abstract: It is shown by counterexample that the correction paper [1] of the paper is incorrect. Following a definition and a theorem, we present a corrected version of the authors' theorem to make the results of the paper precise.

Low order observer for discrete-time systems with slow and fast modes

Abstract: Linear shift-invariant discrete-time systems with slow and fast modes are considered. In particular, investigation of these systems with inadequately modelled but stable fast dynamics, is made. Conditions under which a low-order observer can be designed for estimating the slow states from knowledge of only the degenerate model, are given. A design methodology, which is robust with respect to the neglected fast dynamics, is presented for stabilizing systems satisfying these conditions.

Low-order observer for discrete-time systems with slow and fast modes

Abstract: Linear shift-invariant discrete-time systems with slow and fast modes are considered. In particular, investigation of these systems with inadequately modelled but stable fast dynamics, is made. Conditions under which a low-order observer can be designed for estimating the slow states from knowledge of only the degenerate model, are given. A design methodology, which is robust with respect to the neglected fast dynamics, is presented for stabilizing systems satisfying these conditions.

Relativistically covariant Bohm-Bub hidden-variable theory for spin measurement of a single particle

Abstract: We present a simple first step toward a relativistically covariant generalization of the Bohm-Bub hidden-variable theory. The model is applicable to spin measurement on a single Dirac particle and describes the collapse of the state vector to a spin-up or spin-down state. The essential postulate is that the hidden-variable vector transforms in the same way as the state vector under a Lorentz transformation. This yields a covariant collapse equation, which reduces to the ordinary Bohm-Bub equation for an observer stationary with respect to the particle and shows a time dilated collapse for a moving observer. The model yields the correct quantum transition probabilities for all observers.